mingw: do not treat `COM0` as a reserved file name

[git] / compat / mingw.c

#include "../git-compat-util.h"
#include "win32.h"
#include <conio.h>
#include <wchar.h>
#include "../strbuf.h"
#include "../run-command.h"
#include "../cache.h"
#include "win32/lazyload.h"
#include "../config.h"
#include "dir.h"

#define HCAST(type, handle) ((type)(intptr_t)handle)

static const int delay[] = { 0, 1, 10, 20, 40 };

void open_in_gdb(void)
{
        static struct child_process cp = CHILD_PROCESS_INIT;
        extern char *_pgmptr;

        argv_array_pushl(&cp.args, "mintty", "gdb", NULL);
        argv_array_pushf(&cp.args, "--pid=%d", getpid());
        cp.clean_on_exit = 1;
        if (start_command(&cp) < 0)
                die_errno("Could not start gdb");
        sleep(1);
}

int err_win_to_posix(DWORD winerr)
{
        int error = ENOSYS;
        switch(winerr) {
        case ERROR_ACCESS_DENIED: error = EACCES; break;
        case ERROR_ACCOUNT_DISABLED: error = EACCES; break;
        case ERROR_ACCOUNT_RESTRICTION: error = EACCES; break;
        case ERROR_ALREADY_ASSIGNED: error = EBUSY; break;
        case ERROR_ALREADY_EXISTS: error = EEXIST; break;
        case ERROR_ARITHMETIC_OVERFLOW: error = ERANGE; break;
        case ERROR_BAD_COMMAND: error = EIO; break;
        case ERROR_BAD_DEVICE: error = ENODEV; break;
        case ERROR_BAD_DRIVER_LEVEL: error = ENXIO; break;
        case ERROR_BAD_EXE_FORMAT: error = ENOEXEC; break;
        case ERROR_BAD_FORMAT: error = ENOEXEC; break;
        case ERROR_BAD_LENGTH: error = EINVAL; break;
        case ERROR_BAD_PATHNAME: error = ENOENT; break;
        case ERROR_BAD_PIPE: error = EPIPE; break;
        case ERROR_BAD_UNIT: error = ENODEV; break;
        case ERROR_BAD_USERNAME: error = EINVAL; break;
        case ERROR_BROKEN_PIPE: error = EPIPE; break;
        case ERROR_BUFFER_OVERFLOW: error = ENAMETOOLONG; break;
        case ERROR_BUSY: error = EBUSY; break;
        case ERROR_BUSY_DRIVE: error = EBUSY; break;
        case ERROR_CALL_NOT_IMPLEMENTED: error = ENOSYS; break;
        case ERROR_CANNOT_MAKE: error = EACCES; break;
        case ERROR_CANTOPEN: error = EIO; break;
        case ERROR_CANTREAD: error = EIO; break;
        case ERROR_CANTWRITE: error = EIO; break;
        case ERROR_CRC: error = EIO; break;
        case ERROR_CURRENT_DIRECTORY: error = EACCES; break;
        case ERROR_DEVICE_IN_USE: error = EBUSY; break;
        case ERROR_DEV_NOT_EXIST: error = ENODEV; break;
        case ERROR_DIRECTORY: error = EINVAL; break;
        case ERROR_DIR_NOT_EMPTY: error = ENOTEMPTY; break;
        case ERROR_DISK_CHANGE: error = EIO; break;
        case ERROR_DISK_FULL: error = ENOSPC; break;
        case ERROR_DRIVE_LOCKED: error = EBUSY; break;
        case ERROR_ENVVAR_NOT_FOUND: error = EINVAL; break;
        case ERROR_EXE_MARKED_INVALID: error = ENOEXEC; break;
        case ERROR_FILENAME_EXCED_RANGE: error = ENAMETOOLONG; break;
        case ERROR_FILE_EXISTS: error = EEXIST; break;
        case ERROR_FILE_INVALID: error = ENODEV; break;
        case ERROR_FILE_NOT_FOUND: error = ENOENT; break;
        case ERROR_GEN_FAILURE: error = EIO; break;
        case ERROR_HANDLE_DISK_FULL: error = ENOSPC; break;
        case ERROR_INSUFFICIENT_BUFFER: error = ENOMEM; break;
        case ERROR_INVALID_ACCESS: error = EACCES; break;
        case ERROR_INVALID_ADDRESS: error = EFAULT; break;
        case ERROR_INVALID_BLOCK: error = EFAULT; break;
        case ERROR_INVALID_DATA: error = EINVAL; break;
        case ERROR_INVALID_DRIVE: error = ENODEV; break;
        case ERROR_INVALID_EXE_SIGNATURE: error = ENOEXEC; break;
        case ERROR_INVALID_FLAGS: error = EINVAL; break;
        case ERROR_INVALID_FUNCTION: error = ENOSYS; break;
        case ERROR_INVALID_HANDLE: error = EBADF; break;
        case ERROR_INVALID_LOGON_HOURS: error = EACCES; break;
        case ERROR_INVALID_NAME: error = EINVAL; break;
        case ERROR_INVALID_OWNER: error = EINVAL; break;
        case ERROR_INVALID_PARAMETER: error = EINVAL; break;
        case ERROR_INVALID_PASSWORD: error = EPERM; break;
        case ERROR_INVALID_PRIMARY_GROUP: error = EINVAL; break;
        case ERROR_INVALID_SIGNAL_NUMBER: error = EINVAL; break;
        case ERROR_INVALID_TARGET_HANDLE: error = EIO; break;
        case ERROR_INVALID_WORKSTATION: error = EACCES; break;
        case ERROR_IO_DEVICE: error = EIO; break;
        case ERROR_IO_INCOMPLETE: error = EINTR; break;
        case ERROR_LOCKED: error = EBUSY; break;
        case ERROR_LOCK_VIOLATION: error = EACCES; break;
        case ERROR_LOGON_FAILURE: error = EACCES; break;
        case ERROR_MAPPED_ALIGNMENT: error = EINVAL; break;
        case ERROR_META_EXPANSION_TOO_LONG: error = E2BIG; break;
        case ERROR_MORE_DATA: error = EPIPE; break;
        case ERROR_NEGATIVE_SEEK: error = ESPIPE; break;
        case ERROR_NOACCESS: error = EFAULT; break;
        case ERROR_NONE_MAPPED: error = EINVAL; break;
        case ERROR_NOT_ENOUGH_MEMORY: error = ENOMEM; break;
        case ERROR_NOT_READY: error = EAGAIN; break;
        case ERROR_NOT_SAME_DEVICE: error = EXDEV; break;
        case ERROR_NO_DATA: error = EPIPE; break;
        case ERROR_NO_MORE_SEARCH_HANDLES: error = EIO; break;
        case ERROR_NO_PROC_SLOTS: error = EAGAIN; break;
        case ERROR_NO_SUCH_PRIVILEGE: error = EACCES; break;
        case ERROR_OPEN_FAILED: error = EIO; break;
        case ERROR_OPEN_FILES: error = EBUSY; break;
        case ERROR_OPERATION_ABORTED: error = EINTR; break;
        case ERROR_OUTOFMEMORY: error = ENOMEM; break;
        case ERROR_PASSWORD_EXPIRED: error = EACCES; break;
        case ERROR_PATH_BUSY: error = EBUSY; break;
        case ERROR_PATH_NOT_FOUND: error = ENOENT; break;
        case ERROR_PIPE_BUSY: error = EBUSY; break;
        case ERROR_PIPE_CONNECTED: error = EPIPE; break;
        case ERROR_PIPE_LISTENING: error = EPIPE; break;
        case ERROR_PIPE_NOT_CONNECTED: error = EPIPE; break;
        case ERROR_PRIVILEGE_NOT_HELD: error = EACCES; break;
        case ERROR_READ_FAULT: error = EIO; break;
        case ERROR_SEEK: error = EIO; break;
        case ERROR_SEEK_ON_DEVICE: error = ESPIPE; break;
        case ERROR_SHARING_BUFFER_EXCEEDED: error = ENFILE; break;
        case ERROR_SHARING_VIOLATION: error = EACCES; break;
        case ERROR_STACK_OVERFLOW: error = ENOMEM; break;
        case ERROR_SUCCESS: BUG("err_win_to_posix() called without an error!");
        case ERROR_SWAPERROR: error = ENOENT; break;
        case ERROR_TOO_MANY_MODULES: error = EMFILE; break;
        case ERROR_TOO_MANY_OPEN_FILES: error = EMFILE; break;
        case ERROR_UNRECOGNIZED_MEDIA: error = ENXIO; break;
        case ERROR_UNRECOGNIZED_VOLUME: error = ENODEV; break;
        case ERROR_WAIT_NO_CHILDREN: error = ECHILD; break;
        case ERROR_WRITE_FAULT: error = EIO; break;
        case ERROR_WRITE_PROTECT: error = EROFS; break;
        }
        return error;
}

static inline int is_file_in_use_error(DWORD errcode)
{
        switch (errcode) {
        case ERROR_SHARING_VIOLATION:
        case ERROR_ACCESS_DENIED:
                return 1;
        }

        return 0;
}

static int read_yes_no_answer(void)
{
        char answer[1024];

        if (fgets(answer, sizeof(answer), stdin)) {
                size_t answer_len = strlen(answer);
                int got_full_line = 0, c;

                /* remove the newline */
                if (answer_len >= 2 && answer[answer_len-2] == '\r') {
                        answer[answer_len-2] = '\0';
                        got_full_line = 1;
                } else if (answer_len >= 1 && answer[answer_len-1] == '\n') {
                        answer[answer_len-1] = '\0';
                        got_full_line = 1;
                }
                /* flush the buffer in case we did not get the full line */
                if (!got_full_line)
                        while ((c = getchar()) != EOF && c != '\n')
                                ;
        } else
                /* we could not read, return the
                 * default answer which is no */
                return 0;

        if (tolower(answer[0]) == 'y' && !answer[1])
                return 1;
        if (!strncasecmp(answer, "yes", sizeof(answer)))
                return 1;
        if (tolower(answer[0]) == 'n' && !answer[1])
                return 0;
        if (!strncasecmp(answer, "no", sizeof(answer)))
                return 0;

        /* did not find an answer we understand */
        return -1;
}

static int ask_yes_no_if_possible(const char *format, ...)
{
        char question[4096];
        const char *retry_hook[] = { NULL, NULL, NULL };
        va_list args;

        va_start(args, format);
        vsnprintf(question, sizeof(question), format, args);
        va_end(args);

        if ((retry_hook[0] = mingw_getenv("GIT_ASK_YESNO"))) {
                retry_hook[1] = question;
                return !run_command_v_opt(retry_hook, 0);
        }

        if (!isatty(_fileno(stdin)) || !isatty(_fileno(stderr)))
                return 0;

        while (1) {
                int answer;
                fprintf(stderr, "%s (y/n) ", question);

                if ((answer = read_yes_no_answer()) >= 0)
                        return answer;

                fprintf(stderr, "Sorry, I did not understand your answer. "
                                "Please type 'y' or 'n'\n");
        }
}

/* Windows only */
enum hide_dotfiles_type {
        HIDE_DOTFILES_FALSE = 0,
        HIDE_DOTFILES_TRUE,
        HIDE_DOTFILES_DOTGITONLY
};

static int core_restrict_inherited_handles = -1;
static enum hide_dotfiles_type hide_dotfiles = HIDE_DOTFILES_DOTGITONLY;
static char *unset_environment_variables;

int mingw_core_config(const char *var, const char *value, void *cb)
{
        if (!strcmp(var, "core.hidedotfiles")) {
                if (value && !strcasecmp(value, "dotgitonly"))
                        hide_dotfiles = HIDE_DOTFILES_DOTGITONLY;
                else
                        hide_dotfiles = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp(var, "core.unsetenvvars")) {
                free(unset_environment_variables);
                unset_environment_variables = xstrdup(value);
                return 0;
        }

        if (!strcmp(var, "core.restrictinheritedhandles")) {
                if (value && !strcasecmp(value, "auto"))
                        core_restrict_inherited_handles = -1;
                else
                        core_restrict_inherited_handles =
                                git_config_bool(var, value);
                return 0;
        }

        return 0;
}

/* Normalizes NT paths as returned by some low-level APIs. */
static wchar_t *normalize_ntpath(wchar_t *wbuf)
{
        int i;
        /* fix absolute path prefixes */
        if (wbuf[0] == '\\') {
                /* strip NT namespace prefixes */
                if (!wcsncmp(wbuf, L"\\??\\", 4) ||
                    !wcsncmp(wbuf, L"\\\\?\\", 4))
                        wbuf += 4;
                else if (!wcsnicmp(wbuf, L"\\DosDevices\\", 12))
                        wbuf += 12;
                /* replace remaining '...UNC\' with '\\' */
                if (!wcsnicmp(wbuf, L"UNC\\", 4)) {
                        wbuf += 2;
                        *wbuf = '\\';
                }
        }
        /* convert backslashes to slashes */
        for (i = 0; wbuf[i]; i++)
                if (wbuf[i] == '\\')
                        wbuf[i] = '/';
        return wbuf;
}

int mingw_unlink(const char *pathname)
{
        int ret, tries = 0;
        wchar_t wpathname[MAX_PATH];
        if (xutftowcs_path(wpathname, pathname) < 0)
                return -1;

        /* read-only files cannot be removed */
        _wchmod(wpathname, 0666);
        while ((ret = _wunlink(wpathname)) == -1 && tries < ARRAY_SIZE(delay)) {
                if (!is_file_in_use_error(GetLastError()))
                        break;
                /*
                 * We assume that some other process had the source or
                 * destination file open at the wrong moment and retry.
                 * In order to give the other process a higher chance to
                 * complete its operation, we give up our time slice now.
                 * If we have to retry again, we do sleep a bit.
                 */
                Sleep(delay[tries]);
                tries++;
        }
        while (ret == -1 && is_file_in_use_error(GetLastError()) &&
               ask_yes_no_if_possible("Unlink of file '%s' failed. "
                        "Should I try again?", pathname))
               ret = _wunlink(wpathname);
        return ret;
}

static int is_dir_empty(const wchar_t *wpath)
{
        WIN32_FIND_DATAW findbuf;
        HANDLE handle;
        wchar_t wbuf[MAX_PATH + 2];
        wcscpy(wbuf, wpath);
        wcscat(wbuf, L"\\*");
        handle = FindFirstFileW(wbuf, &findbuf);
        if (handle == INVALID_HANDLE_VALUE)
                return GetLastError() == ERROR_NO_MORE_FILES;

        while (!wcscmp(findbuf.cFileName, L".") ||
                        !wcscmp(findbuf.cFileName, L".."))
                if (!FindNextFileW(handle, &findbuf)) {
                        DWORD err = GetLastError();
                        FindClose(handle);
                        return err == ERROR_NO_MORE_FILES;
                }
        FindClose(handle);
        return 0;
}

int mingw_rmdir(const char *pathname)
{
        int ret, tries = 0;
        wchar_t wpathname[MAX_PATH];
        if (xutftowcs_path(wpathname, pathname) < 0)
                return -1;

        while ((ret = _wrmdir(wpathname)) == -1 && tries < ARRAY_SIZE(delay)) {
                if (!is_file_in_use_error(GetLastError()))
                        errno = err_win_to_posix(GetLastError());
                if (errno != EACCES)
                        break;
                if (!is_dir_empty(wpathname)) {
                        errno = ENOTEMPTY;
                        break;
                }
                /*
                 * We assume that some other process had the source or
                 * destination file open at the wrong moment and retry.
                 * In order to give the other process a higher chance to
                 * complete its operation, we give up our time slice now.
                 * If we have to retry again, we do sleep a bit.
                 */
                Sleep(delay[tries]);
                tries++;
        }
        while (ret == -1 && errno == EACCES && is_file_in_use_error(GetLastError()) &&
               ask_yes_no_if_possible("Deletion of directory '%s' failed. "
                        "Should I try again?", pathname))
               ret = _wrmdir(wpathname);
        return ret;
}

static inline int needs_hiding(const char *path)
{
        const char *basename;

        if (hide_dotfiles == HIDE_DOTFILES_FALSE)
                return 0;

        /* We cannot use basename(), as it would remove trailing slashes */
        win32_skip_dos_drive_prefix((char **)&path);
        if (!*path)
                return 0;

        for (basename = path; *path; path++)
                if (is_dir_sep(*path)) {
                        do {
                                path++;
                        } while (is_dir_sep(*path));
                        /* ignore trailing slashes */
                        if (*path)
                                basename = path;
                        else
                                break;
                }

        if (hide_dotfiles == HIDE_DOTFILES_TRUE)
                return *basename == '.';

        assert(hide_dotfiles == HIDE_DOTFILES_DOTGITONLY);
        return !strncasecmp(".git", basename, 4) &&
                (!basename[4] || is_dir_sep(basename[4]));
}

static int set_hidden_flag(const wchar_t *path, int set)
{
        DWORD original = GetFileAttributesW(path), modified;
        if (set)
                modified = original | FILE_ATTRIBUTE_HIDDEN;
        else
                modified = original & ~FILE_ATTRIBUTE_HIDDEN;
        if (original == modified || SetFileAttributesW(path, modified))
                return 0;
        errno = err_win_to_posix(GetLastError());
        return -1;
}

int mingw_mkdir(const char *path, int mode)
{
        int ret;
        wchar_t wpath[MAX_PATH];

        if (!is_valid_win32_path(path, 0)) {
                errno = EINVAL;
                return -1;
        }

        if (xutftowcs_path(wpath, path) < 0)
                return -1;
        ret = _wmkdir(wpath);
        if (!ret && needs_hiding(path))
                return set_hidden_flag(wpath, 1);
        return ret;
}

/*
 * Calling CreateFile() using FILE_APPEND_DATA and without FILE_WRITE_DATA
 * is documented in [1] as opening a writable file handle in append mode.
 * (It is believed that) this is atomic since it is maintained by the
 * kernel unlike the O_APPEND flag which is racily maintained by the CRT.
 *
 * [1] https://docs.microsoft.com/en-us/windows/desktop/fileio/file-access-rights-constants
 *
 * This trick does not appear to work for named pipes.  Instead it creates
 * a named pipe client handle that cannot be written to.  Callers should
 * just use the regular _wopen() for them.  (And since client handle gets
 * bound to a unique server handle, it isn't really an issue.)
 */
static int mingw_open_append(wchar_t const *wfilename, int oflags, ...)
{
        HANDLE handle;
        int fd;
        DWORD create = (oflags & O_CREAT) ? OPEN_ALWAYS : OPEN_EXISTING;

        /* only these flags are supported */
        if ((oflags & ~O_CREAT) != (O_WRONLY | O_APPEND))
                return errno = ENOSYS, -1;

        /*
         * FILE_SHARE_WRITE is required to permit child processes
         * to append to the file.
         */
        handle = CreateFileW(wfilename, FILE_APPEND_DATA,
                        FILE_SHARE_WRITE | FILE_SHARE_READ,
                        NULL, create, FILE_ATTRIBUTE_NORMAL, NULL);
        if (handle == INVALID_HANDLE_VALUE)
                return errno = err_win_to_posix(GetLastError()), -1;

        /*
         * No O_APPEND here, because the CRT uses it only to reset the
         * file pointer to EOF before each write(); but that is not
         * necessary (and may lead to races) for a file created with
         * FILE_APPEND_DATA.
         */
        fd = _open_osfhandle((intptr_t)handle, O_BINARY);
        if (fd < 0)
                CloseHandle(handle);
        return fd;
}

/*
 * Does the pathname map to the local named pipe filesystem?
 * That is, does it have a "//./pipe/" prefix?
 */
static int is_local_named_pipe_path(const char *filename)
{
        return (is_dir_sep(filename[0]) &&
                is_dir_sep(filename[1]) &&
                filename[2] == '.'  &&
                is_dir_sep(filename[3]) &&
                !strncasecmp(filename+4, "pipe", 4) &&
                is_dir_sep(filename[8]) &&
                filename[9]);
}

int mingw_open (const char *filename, int oflags, ...)
{
        typedef int (*open_fn_t)(wchar_t const *wfilename, int oflags, ...);
        va_list args;
        unsigned mode;
        int fd, create = (oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL);
        wchar_t wfilename[MAX_PATH];
        open_fn_t open_fn;

        va_start(args, oflags);
        mode = va_arg(args, int);
        va_end(args);

        if (!is_valid_win32_path(filename, !create)) {
                errno = create ? EINVAL : ENOENT;
                return -1;
        }

        if ((oflags & O_APPEND) && !is_local_named_pipe_path(filename))
                open_fn = mingw_open_append;
        else
                open_fn = _wopen;

        if (filename && !strcmp(filename, "/dev/null"))
                wcscpy(wfilename, L"nul");
        else if (xutftowcs_path(wfilename, filename) < 0)
                return -1;

        fd = open_fn(wfilename, oflags, mode);

        if (fd < 0 && (oflags & O_ACCMODE) != O_RDONLY && errno == EACCES) {
                DWORD attrs = GetFileAttributesW(wfilename);
                if (attrs != INVALID_FILE_ATTRIBUTES && (attrs & FILE_ATTRIBUTE_DIRECTORY))
                        errno = EISDIR;
        }
        if ((oflags & O_CREAT) && needs_hiding(filename)) {
                /*
                 * Internally, _wopen() uses the CreateFile() API which errors
                 * out with an ERROR_ACCESS_DENIED if CREATE_ALWAYS was
                 * specified and an already existing file's attributes do not
                 * match *exactly*. As there is no mode or flag we can set that
                 * would correspond to FILE_ATTRIBUTE_HIDDEN, let's just try
                 * again *without* the O_CREAT flag (that corresponds to the
                 * CREATE_ALWAYS flag of CreateFile()).
                 */
                if (fd < 0 && errno == EACCES)
                        fd = open_fn(wfilename, oflags & ~O_CREAT, mode);
                if (fd >= 0 && set_hidden_flag(wfilename, 1))
                        warning("could not mark '%s' as hidden.", filename);
        }
        return fd;
}

static BOOL WINAPI ctrl_ignore(DWORD type)
{
        return TRUE;
}

#undef fgetc
int mingw_fgetc(FILE *stream)
{
        int ch;
        if (!isatty(_fileno(stream)))
                return fgetc(stream);

        SetConsoleCtrlHandler(ctrl_ignore, TRUE);
        while (1) {
                ch = fgetc(stream);
                if (ch != EOF || GetLastError() != ERROR_OPERATION_ABORTED)
                        break;

                /* Ctrl+C was pressed, simulate SIGINT and retry */
                mingw_raise(SIGINT);
        }
        SetConsoleCtrlHandler(ctrl_ignore, FALSE);
        return ch;
}

#undef fopen
FILE *mingw_fopen (const char *filename, const char *otype)
{
        int hide = needs_hiding(filename);
        FILE *file;
        wchar_t wfilename[MAX_PATH], wotype[4];
        if (filename && !strcmp(filename, "/dev/null"))
                wcscpy(wfilename, L"nul");
        else if (!is_valid_win32_path(filename, 1)) {
                int create = otype && strchr(otype, 'w');
                errno = create ? EINVAL : ENOENT;
                return NULL;
        } else if (xutftowcs_path(wfilename, filename) < 0)
                return NULL;

        if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
                return NULL;

        if (hide && !access(filename, F_OK) && set_hidden_flag(wfilename, 0)) {
                error("could not unhide %s", filename);
                return NULL;
        }
        file = _wfopen(wfilename, wotype);
        if (!file && GetLastError() == ERROR_INVALID_NAME)
                errno = ENOENT;
        if (file && hide && set_hidden_flag(wfilename, 1))
                warning("could not mark '%s' as hidden.", filename);
        return file;
}

FILE *mingw_freopen (const char *filename, const char *otype, FILE *stream)
{
        int hide = needs_hiding(filename);
        FILE *file;
        wchar_t wfilename[MAX_PATH], wotype[4];
        if (filename && !strcmp(filename, "/dev/null"))
                wcscpy(wfilename, L"nul");
        else if (!is_valid_win32_path(filename, 1)) {
                int create = otype && strchr(otype, 'w');
                errno = create ? EINVAL : ENOENT;
                return NULL;
        } else if (xutftowcs_path(wfilename, filename) < 0)
                return NULL;

        if (xutftowcs(wotype, otype, ARRAY_SIZE(wotype)) < 0)
                return NULL;

        if (hide && !access(filename, F_OK) && set_hidden_flag(wfilename, 0)) {
                error("could not unhide %s", filename);
                return NULL;
        }
        file = _wfreopen(wfilename, wotype, stream);
        if (file && hide && set_hidden_flag(wfilename, 1))
                warning("could not mark '%s' as hidden.", filename);
        return file;
}

#undef fflush
int mingw_fflush(FILE *stream)
{
        int ret = fflush(stream);

        /*
         * write() is used behind the scenes of stdio output functions.
         * Since git code does not check for errors after each stdio write
         * operation, it can happen that write() is called by a later
         * stdio function even if an earlier write() call failed. In the
         * case of a pipe whose readable end was closed, only the first
         * call to write() reports EPIPE on Windows. Subsequent write()
         * calls report EINVAL. It is impossible to notice whether this
         * fflush invocation triggered such a case, therefore, we have to
         * catch all EINVAL errors whole-sale.
         */
        if (ret && errno == EINVAL)
                errno = EPIPE;

        return ret;
}

#undef write
ssize_t mingw_write(int fd, const void *buf, size_t len)
{
        ssize_t result = write(fd, buf, len);

        if (result < 0 && errno == EINVAL && buf) {
                /* check if fd is a pipe */
                HANDLE h = (HANDLE) _get_osfhandle(fd);
                if (GetFileType(h) == FILE_TYPE_PIPE)
                        errno = EPIPE;
                else
                        errno = EINVAL;
        }

        return result;
}

int mingw_access(const char *filename, int mode)
{
        wchar_t wfilename[MAX_PATH];
        if (xutftowcs_path(wfilename, filename) < 0)
                return -1;
        /* X_OK is not supported by the MSVCRT version */
        return _waccess(wfilename, mode & ~X_OK);
}

int mingw_chdir(const char *dirname)
{
        wchar_t wdirname[MAX_PATH];
        if (xutftowcs_path(wdirname, dirname) < 0)
                return -1;
        return _wchdir(wdirname);
}

int mingw_chmod(const char *filename, int mode)
{
        wchar_t wfilename[MAX_PATH];
        if (xutftowcs_path(wfilename, filename) < 0)
                return -1;
        return _wchmod(wfilename, mode);
}

/*
 * The unit of FILETIME is 100-nanoseconds since January 1, 1601, UTC.
 * Returns the 100-nanoseconds ("hekto nanoseconds") since the epoch.
 */
static inline long long filetime_to_hnsec(const FILETIME *ft)
{
        long long winTime = ((long long)ft->dwHighDateTime << 32) + ft->dwLowDateTime;
        /* Windows to Unix Epoch conversion */
        return winTime - 116444736000000000LL;
}

static inline void filetime_to_timespec(const FILETIME *ft, struct timespec *ts)
{
        long long hnsec = filetime_to_hnsec(ft);
        ts->tv_sec = (time_t)(hnsec / 10000000);
        ts->tv_nsec = (hnsec % 10000000) * 100;
}

/**
 * Verifies that safe_create_leading_directories() would succeed.
 */
static int has_valid_directory_prefix(wchar_t *wfilename)
{
        int n = wcslen(wfilename);

        while (n > 0) {
                wchar_t c = wfilename[--n];
                DWORD attributes;

                if (!is_dir_sep(c))
                        continue;

                wfilename[n] = L'\0';
                attributes = GetFileAttributesW(wfilename);
                wfilename[n] = c;
                if (attributes == FILE_ATTRIBUTE_DIRECTORY ||
                                attributes == FILE_ATTRIBUTE_DEVICE)
                        return 1;
                if (attributes == INVALID_FILE_ATTRIBUTES)
                        switch (GetLastError()) {
                        case ERROR_PATH_NOT_FOUND:
                                continue;
                        case ERROR_FILE_NOT_FOUND:
                                /* This implies parent directory exists. */
                                return 1;
                        }
                return 0;
        }
        return 1;
}

/* We keep the do_lstat code in a separate function to avoid recursion.
 * When a path ends with a slash, the stat will fail with ENOENT. In
 * this case, we strip the trailing slashes and stat again.
 *
 * If follow is true then act like stat() and report on the link
 * target. Otherwise report on the link itself.
 */
static int do_lstat(int follow, const char *file_name, struct stat *buf)
{
        WIN32_FILE_ATTRIBUTE_DATA fdata;
        wchar_t wfilename[MAX_PATH];
        if (xutftowcs_path(wfilename, file_name) < 0)
                return -1;

        if (GetFileAttributesExW(wfilename, GetFileExInfoStandard, &fdata)) {
                buf->st_ino = 0;
                buf->st_gid = 0;
                buf->st_uid = 0;
                buf->st_nlink = 1;
                buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes);
                buf->st_size = fdata.nFileSizeLow |
                        (((off_t)fdata.nFileSizeHigh)<<32);
                buf->st_dev = buf->st_rdev = 0; /* not used by Git */
                filetime_to_timespec(&(fdata.ftLastAccessTime), &(buf->st_atim));
                filetime_to_timespec(&(fdata.ftLastWriteTime), &(buf->st_mtim));
                filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim));
                if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
                        WIN32_FIND_DATAW findbuf;
                        HANDLE handle = FindFirstFileW(wfilename, &findbuf);
                        if (handle != INVALID_HANDLE_VALUE) {
                                if ((findbuf.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) &&
                                                (findbuf.dwReserved0 == IO_REPARSE_TAG_SYMLINK)) {
                                        if (follow) {
                                                char buffer[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
                                                buf->st_size = readlink(file_name, buffer, MAXIMUM_REPARSE_DATA_BUFFER_SIZE);
                                        } else {
                                                buf->st_mode = S_IFLNK;
                                        }
                                        buf->st_mode |= S_IREAD;
                                        if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY))
                                                buf->st_mode |= S_IWRITE;
                                }
                                FindClose(handle);
                        }
                }
                return 0;
        }
        switch (GetLastError()) {
        case ERROR_ACCESS_DENIED:
        case ERROR_SHARING_VIOLATION:
        case ERROR_LOCK_VIOLATION:
        case ERROR_SHARING_BUFFER_EXCEEDED:
                errno = EACCES;
                break;
        case ERROR_BUFFER_OVERFLOW:
                errno = ENAMETOOLONG;
                break;
        case ERROR_NOT_ENOUGH_MEMORY:
                errno = ENOMEM;
                break;
        case ERROR_PATH_NOT_FOUND:
                if (!has_valid_directory_prefix(wfilename)) {
                        errno = ENOTDIR;
                        break;
                }
                /* fallthru */
        default:
                errno = ENOENT;
                break;
        }
        return -1;
}

/* We provide our own lstat/fstat functions, since the provided
 * lstat/fstat functions are so slow. These stat functions are
 * tailored for Git's usage (read: fast), and are not meant to be
 * complete. Note that Git stat()s are redirected to mingw_lstat()
 * too, since Windows doesn't really handle symlinks that well.
 */
static int do_stat_internal(int follow, const char *file_name, struct stat *buf)
{
        int namelen;
        char alt_name[PATH_MAX];

        if (!do_lstat(follow, file_name, buf))
                return 0;

        /* if file_name ended in a '/', Windows returned ENOENT;
         * try again without trailing slashes
         */
        if (errno != ENOENT)
                return -1;

        namelen = strlen(file_name);
        if (namelen && file_name[namelen-1] != '/')
                return -1;
        while (namelen && file_name[namelen-1] == '/')
                --namelen;
        if (!namelen || namelen >= PATH_MAX)
                return -1;

        memcpy(alt_name, file_name, namelen);
        alt_name[namelen] = 0;
        return do_lstat(follow, alt_name, buf);
}

static int get_file_info_by_handle(HANDLE hnd, struct stat *buf)
{
        BY_HANDLE_FILE_INFORMATION fdata;

        if (!GetFileInformationByHandle(hnd, &fdata)) {
                errno = err_win_to_posix(GetLastError());
                return -1;
        }

        buf->st_ino = 0;
        buf->st_gid = 0;
        buf->st_uid = 0;
        buf->st_nlink = 1;
        buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes);
        buf->st_size = fdata.nFileSizeLow |
                (((off_t)fdata.nFileSizeHigh)<<32);
        buf->st_dev = buf->st_rdev = 0; /* not used by Git */
        filetime_to_timespec(&(fdata.ftLastAccessTime), &(buf->st_atim));
        filetime_to_timespec(&(fdata.ftLastWriteTime), &(buf->st_mtim));
        filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim));
        return 0;
}

int mingw_lstat(const char *file_name, struct stat *buf)
{
        return do_stat_internal(0, file_name, buf);
}
int mingw_stat(const char *file_name, struct stat *buf)
{
        return do_stat_internal(1, file_name, buf);
}

int mingw_fstat(int fd, struct stat *buf)
{
        HANDLE fh = (HANDLE)_get_osfhandle(fd);
        DWORD avail, type = GetFileType(fh) & ~FILE_TYPE_REMOTE;

        switch (type) {
        case FILE_TYPE_DISK:
                return get_file_info_by_handle(fh, buf);

        case FILE_TYPE_CHAR:
        case FILE_TYPE_PIPE:
                /* initialize stat fields */
                memset(buf, 0, sizeof(*buf));
                buf->st_nlink = 1;

                if (type == FILE_TYPE_CHAR) {
                        buf->st_mode = _S_IFCHR;
                } else {
                        buf->st_mode = _S_IFIFO;
                        if (PeekNamedPipe(fh, NULL, 0, NULL, &avail, NULL))
                                buf->st_size = avail;
                }
                return 0;

        default:
                errno = EBADF;
                return -1;
        }
}

static inline void time_t_to_filetime(time_t t, FILETIME *ft)
{
        long long winTime = t * 10000000LL + 116444736000000000LL;
        ft->dwLowDateTime = winTime;
        ft->dwHighDateTime = winTime >> 32;
}

int mingw_utime (const char *file_name, const struct utimbuf *times)
{
        FILETIME mft, aft;
        int fh, rc;
        DWORD attrs;
        wchar_t wfilename[MAX_PATH];
        if (xutftowcs_path(wfilename, file_name) < 0)
                return -1;

        /* must have write permission */
        attrs = GetFileAttributesW(wfilename);
        if (attrs != INVALID_FILE_ATTRIBUTES &&
            (attrs & FILE_ATTRIBUTE_READONLY)) {
                /* ignore errors here; open() will report them */
                SetFileAttributesW(wfilename, attrs & ~FILE_ATTRIBUTE_READONLY);
        }

        if ((fh = _wopen(wfilename, O_RDWR | O_BINARY)) < 0) {
                rc = -1;
                goto revert_attrs;
        }

        if (times) {
                time_t_to_filetime(times->modtime, &mft);
                time_t_to_filetime(times->actime, &aft);
        } else {
                GetSystemTimeAsFileTime(&mft);
                aft = mft;
        }
        if (!SetFileTime((HANDLE)_get_osfhandle(fh), NULL, &aft, &mft)) {
                errno = EINVAL;
                rc = -1;
        } else
                rc = 0;
        close(fh);

revert_attrs:
        if (attrs != INVALID_FILE_ATTRIBUTES &&
            (attrs & FILE_ATTRIBUTE_READONLY)) {
                /* ignore errors again */
                SetFileAttributesW(wfilename, attrs);
        }
        return rc;
}

#undef strftime
size_t mingw_strftime(char *s, size_t max,
                      const char *format, const struct tm *tm)
{
        /* a pointer to the original strftime in case we can't find the UCRT version */
        static size_t (*fallback)(char *, size_t, const char *, const struct tm *) = strftime;
        size_t ret;
        DECLARE_PROC_ADDR(ucrtbase.dll, size_t, strftime, char *, size_t,
                const char *, const struct tm *);

        if (INIT_PROC_ADDR(strftime))
                ret = strftime(s, max, format, tm);
        else
                ret = fallback(s, max, format, tm);

        if (!ret && errno == EINVAL)
                die("invalid strftime format: '%s'", format);
        return ret;
}

unsigned int sleep (unsigned int seconds)
{
        Sleep(seconds*1000);
        return 0;
}

char *mingw_mktemp(char *template)
{
        wchar_t wtemplate[MAX_PATH];
        if (xutftowcs_path(wtemplate, template) < 0)
                return NULL;
        if (!_wmktemp(wtemplate))
                return NULL;
        if (xwcstoutf(template, wtemplate, strlen(template) + 1) < 0)
                return NULL;
        return template;
}

int mkstemp(char *template)
{
        char *filename = mktemp(template);
        if (filename == NULL)
                return -1;
        return open(filename, O_RDWR | O_CREAT, 0600);
}

int gettimeofday(struct timeval *tv, void *tz)
{
        FILETIME ft;
        long long hnsec;

        GetSystemTimeAsFileTime(&ft);
        hnsec = filetime_to_hnsec(&ft);
        tv->tv_sec = hnsec / 10000000;
        tv->tv_usec = (hnsec % 10000000) / 10;
        return 0;
}

int pipe(int filedes[2])
{
        HANDLE h[2];

        /* this creates non-inheritable handles */
        if (!CreatePipe(&h[0], &h[1], NULL, 8192)) {
                errno = err_win_to_posix(GetLastError());
                return -1;
        }
        filedes[0] = _open_osfhandle(HCAST(int, h[0]), O_NOINHERIT);
        if (filedes[0] < 0) {
                CloseHandle(h[0]);
                CloseHandle(h[1]);
                return -1;
        }
        filedes[1] = _open_osfhandle(HCAST(int, h[1]), O_NOINHERIT);
        if (filedes[1] < 0) {
                close(filedes[0]);
                CloseHandle(h[1]);
                return -1;
        }
        return 0;
}

struct tm *gmtime_r(const time_t *timep, struct tm *result)
{
        if (gmtime_s(result, timep) == 0)
                return result;
        return NULL;
}

struct tm *localtime_r(const time_t *timep, struct tm *result)
{
        if (localtime_s(result, timep) == 0)
                return result;
        return NULL;
}

char *mingw_getcwd(char *pointer, int len)
{
        wchar_t cwd[MAX_PATH], wpointer[MAX_PATH];
        DWORD ret = GetCurrentDirectoryW(ARRAY_SIZE(cwd), cwd);

        if (!ret || ret >= ARRAY_SIZE(cwd)) {
                errno = ret ? ENAMETOOLONG : err_win_to_posix(GetLastError());
                return NULL;
        }
        ret = GetLongPathNameW(cwd, wpointer, ARRAY_SIZE(wpointer));
        if (!ret && GetLastError() == ERROR_ACCESS_DENIED) {
                HANDLE hnd = CreateFileW(cwd, 0,
                        FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL,
                        OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
                if (hnd == INVALID_HANDLE_VALUE)
                        return NULL;
                ret = GetFinalPathNameByHandleW(hnd, wpointer, ARRAY_SIZE(wpointer), 0);
                CloseHandle(hnd);
                if (!ret || ret >= ARRAY_SIZE(wpointer))
                        return NULL;
                if (xwcstoutf(pointer, normalize_ntpath(wpointer), len) < 0)
                        return NULL;
                return pointer;
        }
        if (!ret || ret >= ARRAY_SIZE(wpointer))
                return NULL;
        if (xwcstoutf(pointer, wpointer, len) < 0)
                return NULL;
        convert_slashes(pointer);
        return pointer;
}

/*
 * See "Parsing C++ Command-Line Arguments" at Microsoft's Docs:
 * https://docs.microsoft.com/en-us/cpp/cpp/parsing-cpp-command-line-arguments
 */
static const char *quote_arg_msvc(const char *arg)
{
        /* count chars to quote */
        int len = 0, n = 0;
        int force_quotes = 0;
        char *q, *d;
        const char *p = arg;
        if (!*p) force_quotes = 1;
        while (*p) {
                if (isspace(*p) || *p == '*' || *p == '?' || *p == '{' || *p == '\'')
                        force_quotes = 1;
                else if (*p == '"')
                        n++;
                else if (*p == '\\') {
                        int count = 0;
                        while (*p == '\\') {
                                count++;
                                p++;
                                len++;
                        }
                        if (*p == '"' || !*p)
                                n += count*2 + 1;
                        continue;
                }
                len++;
                p++;
        }
        if (!force_quotes && n == 0)
                return arg;

        /* insert \ where necessary */
        d = q = xmalloc(st_add3(len, n, 3));
        *d++ = '"';
        while (*arg) {
                if (*arg == '"')
                        *d++ = '\\';
                else if (*arg == '\\') {
                        int count = 0;
                        while (*arg == '\\') {
                                count++;
                                *d++ = *arg++;
                        }
                        if (*arg == '"' || !*arg) {
                                while (count-- > 0)
                                        *d++ = '\\';
                                /* don't escape the surrounding end quote */
                                if (!*arg)
                                        break;
                                *d++ = '\\';
                        }
                }
                *d++ = *arg++;
        }
        *d++ = '"';
        *d++ = '\0';
        return q;
}

#include "quote.h"

static const char *quote_arg_msys2(const char *arg)
{
        struct strbuf buf = STRBUF_INIT;
        const char *p2 = arg, *p;

        for (p = arg; *p; p++) {
                int ws = isspace(*p);
                if (!ws && *p != '\\' && *p != '"' && *p != '{' && *p != '\'' &&
                    *p != '?' && *p != '*' && *p != '~')
                        continue;
                if (!buf.len)
                        strbuf_addch(&buf, '"');
                if (p != p2)
                        strbuf_add(&buf, p2, p - p2);
                if (*p == '\\' || *p == '"')
                        strbuf_addch(&buf, '\\');
                p2 = p;
        }

        if (p == arg)
                strbuf_addch(&buf, '"');
        else if (!buf.len)
                return arg;
        else
                strbuf_add(&buf, p2, p - p2);

        strbuf_addch(&buf, '"');
        return strbuf_detach(&buf, 0);
}

static const char *parse_interpreter(const char *cmd)
{
        static char buf[100];
        char *p, *opt;
        int n, fd;

        /* don't even try a .exe */
        n = strlen(cmd);
        if (n >= 4 && !strcasecmp(cmd+n-4, ".exe"))
                return NULL;

        fd = open(cmd, O_RDONLY);
        if (fd < 0)
                return NULL;
        n = read(fd, buf, sizeof(buf)-1);
        close(fd);
        if (n < 4)      /* at least '#!/x' and not error */
                return NULL;

        if (buf[0] != '#' || buf[1] != '!')
                return NULL;
        buf[n] = '\0';
        p = buf + strcspn(buf, "\r\n");
        if (!*p)
                return NULL;

        *p = '\0';
        if (!(p = strrchr(buf+2, '/')) && !(p = strrchr(buf+2, '\\')))
                return NULL;
        /* strip options */
        if ((opt = strchr(p+1, ' ')))
                *opt = '\0';
        return p+1;
}

/*
 * exe_only means that we only want to detect .exe files, but not scripts
 * (which do not have an extension)
 */
static char *lookup_prog(const char *dir, int dirlen, const char *cmd,
                         int isexe, int exe_only)
{
        char path[MAX_PATH];
        wchar_t wpath[MAX_PATH];
        snprintf(path, sizeof(path), "%.*s\\%s.exe", dirlen, dir, cmd);

        if (xutftowcs_path(wpath, path) < 0)
                return NULL;

        if (!isexe && _waccess(wpath, F_OK) == 0)
                return xstrdup(path);
        wpath[wcslen(wpath)-4] = '\0';
        if ((!exe_only || isexe) && _waccess(wpath, F_OK) == 0) {
                if (!(GetFileAttributesW(wpath) & FILE_ATTRIBUTE_DIRECTORY)) {
                        path[strlen(path)-4] = '\0';
                        return xstrdup(path);
                }
        }
        return NULL;
}

/*
 * Determines the absolute path of cmd using the split path in path.
 * If cmd contains a slash or backslash, no lookup is performed.
 */
static char *path_lookup(const char *cmd, int exe_only)
{
        const char *path;
        char *prog = NULL;
        int len = strlen(cmd);
        int isexe = len >= 4 && !strcasecmp(cmd+len-4, ".exe");

        if (strpbrk(cmd, "/\\"))
                return xstrdup(cmd);

        path = mingw_getenv("PATH");
        if (!path)
                return NULL;

        while (!prog) {
                const char *sep = strchrnul(path, ';');
                int dirlen = sep - path;
                if (dirlen)
                        prog = lookup_prog(path, dirlen, cmd, isexe, exe_only);
                if (!*sep)
                        break;
                path = sep + 1;
        }

        return prog;
}

static const wchar_t *wcschrnul(const wchar_t *s, wchar_t c)
{
        while (*s && *s != c)
                s++;
        return s;
}

/* Compare only keys */
static int wenvcmp(const void *a, const void *b)
{
        wchar_t *p = *(wchar_t **)a, *q = *(wchar_t **)b;
        size_t p_len, q_len;

        /* Find the keys */
        p_len = wcschrnul(p, L'=') - p;
        q_len = wcschrnul(q, L'=') - q;

        /* If the length differs, include the shorter key's NUL */
        if (p_len < q_len)
                p_len++;
        else if (p_len > q_len)
                p_len = q_len + 1;

        return _wcsnicmp(p, q, p_len);
}

/*
 * Build an environment block combining the inherited environment
 * merged with the given list of settings.
 *
 * Values of the form "KEY=VALUE" in deltaenv override inherited values.
 * Values of the form "KEY" in deltaenv delete inherited values.
 *
 * Multiple entries in deltaenv for the same key are explicitly allowed.
 *
 * We return a contiguous block of UNICODE strings with a final trailing
 * zero word.
 */
static wchar_t *make_environment_block(char **deltaenv)
{
        wchar_t *wenv = GetEnvironmentStringsW(), *wdeltaenv, *result, *p;
        size_t wlen, s, delta_size, size;

        wchar_t **array = NULL;
        size_t alloc = 0, nr = 0, i;

        size = 1; /* for extra NUL at the end */

        /* If there is no deltaenv to apply, simply return a copy. */
        if (!deltaenv || !*deltaenv) {
                for (p = wenv; p && *p; ) {
                        size_t s = wcslen(p) + 1;
                        size += s;
                        p += s;
                }

                ALLOC_ARRAY(result, size);
                COPY_ARRAY(result, wenv, size);
                FreeEnvironmentStringsW(wenv);
                return result;
        }

        /*
         * If there is a deltaenv, let's accumulate all keys into `array`,
         * sort them using the stable git_stable_qsort() and then copy,
         * skipping duplicate keys
         */
        for (p = wenv; p && *p; ) {
                ALLOC_GROW(array, nr + 1, alloc);
                s = wcslen(p) + 1;
                array[nr++] = p;
                p += s;
                size += s;
        }

        /* (over-)assess size needed for wchar version of deltaenv */
        for (delta_size = 0, i = 0; deltaenv[i]; i++)
                delta_size += strlen(deltaenv[i]) * 2 + 1;
        ALLOC_ARRAY(wdeltaenv, delta_size);

        /* convert the deltaenv, appending to array */
        for (i = 0, p = wdeltaenv; deltaenv[i]; i++) {
                ALLOC_GROW(array, nr + 1, alloc);
                wlen = xutftowcs(p, deltaenv[i], wdeltaenv + delta_size - p);
                array[nr++] = p;
                p += wlen + 1;
        }

        git_stable_qsort(array, nr, sizeof(*array), wenvcmp);
        ALLOC_ARRAY(result, size + delta_size);

        for (p = result, i = 0; i < nr; i++) {
                /* Skip any duplicate keys; last one wins */
                while (i + 1 < nr && !wenvcmp(array + i, array + i + 1))
                       i++;

                /* Skip "to delete" entry */
                if (!wcschr(array[i], L'='))
                        continue;

                size = wcslen(array[i]) + 1;
                COPY_ARRAY(p, array[i], size);
                p += size;
        }
        *p = L'\0';

        free(array);
        free(wdeltaenv);
        FreeEnvironmentStringsW(wenv);
        return result;
}

static void do_unset_environment_variables(void)
{
        static int done;
        char *p = unset_environment_variables;

        if (done || !p)
                return;
        done = 1;

        for (;;) {
                char *comma = strchr(p, ',');

                if (comma)
                        *comma = '\0';
                unsetenv(p);
                if (!comma)
                        break;
                p = comma + 1;
        }
}

struct pinfo_t {
        struct pinfo_t *next;
        pid_t pid;
        HANDLE proc;
};
static struct pinfo_t *pinfo = NULL;
CRITICAL_SECTION pinfo_cs;

/* Used to match and chomp off path components */
static inline int match_last_path_component(const char *path, size_t *len,
                                            const char *component)
{
        size_t component_len = strlen(component);
        if (*len < component_len + 1 ||
            !is_dir_sep(path[*len - component_len - 1]) ||
            fspathncmp(path + *len - component_len, component, component_len))
                return 0;
        *len -= component_len + 1;
        /* chomp off repeated dir separators */
        while (*len > 0 && is_dir_sep(path[*len - 1]))
                (*len)--;
        return 1;
}

static int is_msys2_sh(const char *cmd)
{
        if (!cmd)
                return 0;

        if (!strcmp(cmd, "sh")) {
                static int ret = -1;
                char *p;

                if (ret >= 0)
                        return ret;

                p = path_lookup(cmd, 0);
                if (!p)
                        ret = 0;
                else {
                        size_t len = strlen(p);

                        ret = match_last_path_component(p, &len, "sh.exe") &&
                                match_last_path_component(p, &len, "bin") &&
                                match_last_path_component(p, &len, "usr");
                        free(p);
                }
                return ret;
        }

        if (ends_with(cmd, "\\sh.exe")) {
                static char *sh;

                if (!sh)
                        sh = path_lookup("sh", 0);

                return !fspathcmp(cmd, sh);
        }

        return 0;
}

static pid_t mingw_spawnve_fd(const char *cmd, const char **argv, char **deltaenv,
                              const char *dir,
                              int prepend_cmd, int fhin, int fhout, int fherr)
{
        static int restrict_handle_inheritance = -1;
        STARTUPINFOEXW si;
        PROCESS_INFORMATION pi;
        LPPROC_THREAD_ATTRIBUTE_LIST attr_list = NULL;
        HANDLE stdhandles[3];
        DWORD stdhandles_count = 0;
        SIZE_T size;
        struct strbuf args;
        wchar_t wcmd[MAX_PATH], wdir[MAX_PATH], *wargs, *wenvblk = NULL;
        unsigned flags = CREATE_UNICODE_ENVIRONMENT;
        BOOL ret;
        HANDLE cons;
        const char *(*quote_arg)(const char *arg) =
                is_msys2_sh(cmd ? cmd : *argv) ?
                quote_arg_msys2 : quote_arg_msvc;

        /* Make sure to override previous errors, if any */
        errno = 0;

        if (restrict_handle_inheritance < 0)
                restrict_handle_inheritance = core_restrict_inherited_handles;
        /*
         * The following code to restrict which handles are inherited seems
         * to work properly only on Windows 7 and later, so let's disable it
         * on Windows Vista and 2008.
         */
        if (restrict_handle_inheritance < 0)
                restrict_handle_inheritance = GetVersion() >> 16 >= 7601;

        do_unset_environment_variables();

        /* Determine whether or not we are associated to a console */
        cons = CreateFileW(L"CONOUT$", GENERIC_WRITE,
                        FILE_SHARE_WRITE, NULL, OPEN_EXISTING,
                        FILE_ATTRIBUTE_NORMAL, NULL);
        if (cons == INVALID_HANDLE_VALUE) {
                /* There is no console associated with this process.
                 * Since the child is a console process, Windows
                 * would normally create a console window. But
                 * since we'll be redirecting std streams, we do
                 * not need the console.
                 * It is necessary to use DETACHED_PROCESS
                 * instead of CREATE_NO_WINDOW to make ssh
                 * recognize that it has no console.
                 */
                flags |= DETACHED_PROCESS;
        } else {
                /* There is already a console. If we specified
                 * DETACHED_PROCESS here, too, Windows would
                 * disassociate the child from the console.
                 * The same is true for CREATE_NO_WINDOW.
                 * Go figure!
                 */
                CloseHandle(cons);
        }
        memset(&si, 0, sizeof(si));
        si.StartupInfo.cb = sizeof(si);
        si.StartupInfo.hStdInput = winansi_get_osfhandle(fhin);
        si.StartupInfo.hStdOutput = winansi_get_osfhandle(fhout);
        si.StartupInfo.hStdError = winansi_get_osfhandle(fherr);

        /* The list of handles cannot contain duplicates */
        if (si.StartupInfo.hStdInput != INVALID_HANDLE_VALUE)
                stdhandles[stdhandles_count++] = si.StartupInfo.hStdInput;
        if (si.StartupInfo.hStdOutput != INVALID_HANDLE_VALUE &&
            si.StartupInfo.hStdOutput != si.StartupInfo.hStdInput)
                stdhandles[stdhandles_count++] = si.StartupInfo.hStdOutput;
        if (si.StartupInfo.hStdError != INVALID_HANDLE_VALUE &&
            si.StartupInfo.hStdError != si.StartupInfo.hStdInput &&
            si.StartupInfo.hStdError != si.StartupInfo.hStdOutput)
                stdhandles[stdhandles_count++] = si.StartupInfo.hStdError;
        if (stdhandles_count)
                si.StartupInfo.dwFlags |= STARTF_USESTDHANDLES;

        if (*argv && !strcmp(cmd, *argv))
                wcmd[0] = L'\0';
        else if (xutftowcs_path(wcmd, cmd) < 0)
                return -1;
        if (dir && xutftowcs_path(wdir, dir) < 0)
                return -1;

        /* concatenate argv, quoting args as we go */
        strbuf_init(&args, 0);
        if (prepend_cmd) {
                char *quoted = (char *)quote_arg(cmd);
                strbuf_addstr(&args, quoted);
                if (quoted != cmd)
                        free(quoted);
        }
        for (; *argv; argv++) {
                char *quoted = (char *)quote_arg(*argv);
                if (*args.buf)
                        strbuf_addch(&args, ' ');
                strbuf_addstr(&args, quoted);
                if (quoted != *argv)
                        free(quoted);
        }

        ALLOC_ARRAY(wargs, st_add(st_mult(2, args.len), 1));
        xutftowcs(wargs, args.buf, 2 * args.len + 1);
        strbuf_release(&args);

        wenvblk = make_environment_block(deltaenv);

        memset(&pi, 0, sizeof(pi));
        if (restrict_handle_inheritance && stdhandles_count &&
            (InitializeProcThreadAttributeList(NULL, 1, 0, &size) ||
             GetLastError() == ERROR_INSUFFICIENT_BUFFER) &&
            (attr_list = (LPPROC_THREAD_ATTRIBUTE_LIST)
                        (HeapAlloc(GetProcessHeap(), 0, size))) &&
            InitializeProcThreadAttributeList(attr_list, 1, 0, &size) &&
            UpdateProcThreadAttribute(attr_list, 0,
                                      PROC_THREAD_ATTRIBUTE_HANDLE_LIST,
                                      stdhandles,
                                      stdhandles_count * sizeof(HANDLE),
                                      NULL, NULL)) {
                si.lpAttributeList = attr_list;
                flags |= EXTENDED_STARTUPINFO_PRESENT;
        }

        ret = CreateProcessW(*wcmd ? wcmd : NULL, wargs, NULL, NULL,
                             stdhandles_count ? TRUE : FALSE,
                             flags, wenvblk, dir ? wdir : NULL,
                             &si.StartupInfo, &pi);

        /*
         * On Windows 2008 R2, it seems that specifying certain types of handles
         * (such as FILE_TYPE_CHAR or FILE_TYPE_PIPE) will always produce an
         * error. Rather than playing finicky and fragile games, let's just try
         * to detect this situation and simply try again without restricting any
         * handle inheritance. This is still better than failing to create
         * processes.
         */
        if (!ret && restrict_handle_inheritance && stdhandles_count) {
                DWORD err = GetLastError();
                struct strbuf buf = STRBUF_INIT;

                if (err != ERROR_NO_SYSTEM_RESOURCES &&
                    /*
                     * On Windows 7 and earlier, handles on pipes and character
                     * devices are inherited automatically, and cannot be
                     * specified in the thread handle list. Rather than trying
                     * to catch each and every corner case (and running the
                     * chance of *still* forgetting a few), let's just fall
                     * back to creating the process without trying to limit the
                     * handle inheritance.
                     */
                    !(err == ERROR_INVALID_PARAMETER &&
                      GetVersion() >> 16 < 9200) &&
                    !getenv("SUPPRESS_HANDLE_INHERITANCE_WARNING")) {
                        DWORD fl = 0;
                        int i;

                        setenv("SUPPRESS_HANDLE_INHERITANCE_WARNING", "1", 1);

                        for (i = 0; i < stdhandles_count; i++) {
                                HANDLE h = stdhandles[i];
                                strbuf_addf(&buf, "handle #%d: %p (type %lx, "
                                            "handle info (%d) %lx\n", i, h,
                                            GetFileType(h),
                                            GetHandleInformation(h, &fl),
                                            fl);
                        }
                        strbuf_addstr(&buf, "\nThis is a bug; please report it "
                                      "at\nhttps://github.com/git-for-windows/"
                                      "git/issues/new\n\n"
                                      "To suppress this warning, please set "
                                      "the environment variable\n\n"
                                      "\tSUPPRESS_HANDLE_INHERITANCE_WARNING=1"
                                      "\n");
                }
                restrict_handle_inheritance = 0;
                flags &= ~EXTENDED_STARTUPINFO_PRESENT;
                ret = CreateProcessW(*wcmd ? wcmd : NULL, wargs, NULL, NULL,
                                     TRUE, flags, wenvblk, dir ? wdir : NULL,
                                     &si.StartupInfo, &pi);
                if (!ret)
                        errno = err_win_to_posix(GetLastError());
                if (ret && buf.len) {
                        warning("failed to restrict file handles (%ld)\n\n%s",
                                err, buf.buf);
                }
                strbuf_release(&buf);
        } else if (!ret)
                errno = err_win_to_posix(GetLastError());

        if (si.lpAttributeList)
                DeleteProcThreadAttributeList(si.lpAttributeList);
        if (attr_list)
                HeapFree(GetProcessHeap(), 0, attr_list);

        free(wenvblk);
        free(wargs);

        if (!ret)
                return -1;

        CloseHandle(pi.hThread);

        /*
         * The process ID is the human-readable identifier of the process
         * that we want to present in log and error messages. The handle
         * is not useful for this purpose. But we cannot close it, either,
         * because it is not possible to turn a process ID into a process
         * handle after the process terminated.
         * Keep the handle in a list for waitpid.
         */
        EnterCriticalSection(&pinfo_cs);
        {
                struct pinfo_t *info = xmalloc(sizeof(struct pinfo_t));
                info->pid = pi.dwProcessId;
                info->proc = pi.hProcess;
                info->next = pinfo;
                pinfo = info;
        }
        LeaveCriticalSection(&pinfo_cs);

        return (pid_t)pi.dwProcessId;
}

static pid_t mingw_spawnv(const char *cmd, const char **argv, int prepend_cmd)
{
        return mingw_spawnve_fd(cmd, argv, NULL, NULL, prepend_cmd, 0, 1, 2);
}

pid_t mingw_spawnvpe(const char *cmd, const char **argv, char **deltaenv,
                     const char *dir,
                     int fhin, int fhout, int fherr)
{
        pid_t pid;
        char *prog = path_lookup(cmd, 0);

        if (!prog) {
                errno = ENOENT;
                pid = -1;
        }
        else {
                const char *interpr = parse_interpreter(prog);

                if (interpr) {
                        const char *argv0 = argv[0];
                        char *iprog = path_lookup(interpr, 1);
                        argv[0] = prog;
                        if (!iprog) {
                                errno = ENOENT;
                                pid = -1;
                        }
                        else {
                                pid = mingw_spawnve_fd(iprog, argv, deltaenv, dir, 1,
                                                       fhin, fhout, fherr);
                                free(iprog);
                        }
                        argv[0] = argv0;
                }
                else
                        pid = mingw_spawnve_fd(prog, argv, deltaenv, dir, 0,
                                               fhin, fhout, fherr);
                free(prog);
        }
        return pid;
}

static int try_shell_exec(const char *cmd, char *const *argv)
{
        const char *interpr = parse_interpreter(cmd);
        char *prog;
        int pid = 0;

        if (!interpr)
                return 0;
        prog = path_lookup(interpr, 1);
        if (prog) {
                int exec_id;
                int argc = 0;
#ifndef _MSC_VER
                const
#endif
                char **argv2;
                while (argv[argc]) argc++;
                ALLOC_ARRAY(argv2, argc + 1);
                argv2[0] = (char *)cmd; /* full path to the script file */
                COPY_ARRAY(&argv2[1], &argv[1], argc);
                exec_id = trace2_exec(prog, argv2);
                pid = mingw_spawnv(prog, argv2, 1);
                if (pid >= 0) {
                        int status;
                        if (waitpid(pid, &status, 0) < 0)
                                status = 255;
                        trace2_exec_result(exec_id, status);
                        exit(status);
                }
                trace2_exec_result(exec_id, -1);
                pid = 1;        /* indicate that we tried but failed */
                free(prog);
                free(argv2);
        }
        return pid;
}

int mingw_execv(const char *cmd, char *const *argv)
{
        /* check if git_command is a shell script */
        if (!try_shell_exec(cmd, argv)) {
                int pid, status;
                int exec_id;

                exec_id = trace2_exec(cmd, (const char **)argv);
                pid = mingw_spawnv(cmd, (const char **)argv, 0);
                if (pid < 0) {
                        trace2_exec_result(exec_id, -1);
                        return -1;
                }
                if (waitpid(pid, &status, 0) < 0)
                        status = 255;
                trace2_exec_result(exec_id, status);
                exit(status);
        }
        return -1;
}

int mingw_execvp(const char *cmd, char *const *argv)
{
        char *prog = path_lookup(cmd, 0);

        if (prog) {
                mingw_execv(prog, argv);
                free(prog);
        } else
                errno = ENOENT;

        return -1;
}

int mingw_kill(pid_t pid, int sig)
{
        if (pid > 0 && sig == SIGTERM) {
                HANDLE h = OpenProcess(PROCESS_TERMINATE, FALSE, pid);

                if (TerminateProcess(h, -1)) {
                        CloseHandle(h);
                        return 0;
                }

                errno = err_win_to_posix(GetLastError());
                CloseHandle(h);
                return -1;
        } else if (pid > 0 && sig == 0) {
                HANDLE h = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, pid);
                if (h) {
                        CloseHandle(h);
                        return 0;
                }
        }

        errno = EINVAL;
        return -1;
}

/*
 * UTF-8 versions of getenv(), putenv() and unsetenv().
 * Internally, they use the CRT's stock UNICODE routines
 * to avoid data loss.
 */
char *mingw_getenv(const char *name)
{
#define GETENV_MAX_RETAIN 64
        static char *values[GETENV_MAX_RETAIN];
        static int value_counter;
        int len_key, len_value;
        wchar_t *w_key;
        char *value;
        wchar_t w_value[32768];

        if (!name || !*name)
                return NULL;

        len_key = strlen(name) + 1;
        /* We cannot use xcalloc() here because that uses getenv() itself */
        w_key = calloc(len_key, sizeof(wchar_t));
        if (!w_key)
                die("Out of memory, (tried to allocate %u wchar_t's)", len_key);
        xutftowcs(w_key, name, len_key);
        /* GetEnvironmentVariableW() only sets the last error upon failure */
        SetLastError(ERROR_SUCCESS);
        len_value = GetEnvironmentVariableW(w_key, w_value, ARRAY_SIZE(w_value));
        if (!len_value && GetLastError() == ERROR_ENVVAR_NOT_FOUND) {
                free(w_key);
                return NULL;
        }
        free(w_key);

        len_value = len_value * 3 + 1;
        /* We cannot use xcalloc() here because that uses getenv() itself */
        value = calloc(len_value, sizeof(char));
        if (!value)
                die("Out of memory, (tried to allocate %u bytes)", len_value);
        xwcstoutf(value, w_value, len_value);

        /*
         * We return `value` which is an allocated value and the caller is NOT
         * expecting to have to free it, so we keep a round-robin array,
         * invalidating the buffer after GETENV_MAX_RETAIN getenv() calls.
         */
        free(values[value_counter]);
        values[value_counter++] = value;
        if (value_counter >= ARRAY_SIZE(values))
                value_counter = 0;

        return value;
}

int mingw_putenv(const char *namevalue)
{
        int size;
        wchar_t *wide, *equal;
        BOOL result;

        if (!namevalue || !*namevalue)
                return 0;

        size = strlen(namevalue) * 2 + 1;
        wide = calloc(size, sizeof(wchar_t));
        if (!wide)
                die("Out of memory, (tried to allocate %u wchar_t's)", size);
        xutftowcs(wide, namevalue, size);
        equal = wcschr(wide, L'=');
        if (!equal)
                result = SetEnvironmentVariableW(wide, NULL);
        else {
                *equal = L'\0';
                result = SetEnvironmentVariableW(wide, equal + 1);
        }
        free(wide);

        if (!result)
                errno = err_win_to_posix(GetLastError());

        return result ? 0 : -1;
}

static void ensure_socket_initialization(void)
{
        WSADATA wsa;
        static int initialized = 0;

        if (initialized)
                return;

        if (WSAStartup(MAKEWORD(2,2), &wsa))
                die("unable to initialize winsock subsystem, error %d",
                        WSAGetLastError());

        atexit((void(*)(void)) WSACleanup);
        initialized = 1;
}

#undef gethostname
int mingw_gethostname(char *name, int namelen)
{
    ensure_socket_initialization();
    return gethostname(name, namelen);
}

#undef gethostbyname
struct hostent *mingw_gethostbyname(const char *host)
{
        ensure_socket_initialization();
        return gethostbyname(host);
}

#undef getaddrinfo
int mingw_getaddrinfo(const char *node, const char *service,
                      const struct addrinfo *hints, struct addrinfo **res)
{
        ensure_socket_initialization();
        return getaddrinfo(node, service, hints, res);
}

int mingw_socket(int domain, int type, int protocol)
{
        int sockfd;
        SOCKET s;

        ensure_socket_initialization();
        s = WSASocket(domain, type, protocol, NULL, 0, 0);
        if (s == INVALID_SOCKET) {
                /*
                 * WSAGetLastError() values are regular BSD error codes
                 * biased by WSABASEERR.
                 * However, strerror() does not know about networking
                 * specific errors, which are values beginning at 38 or so.
                 * Therefore, we choose to leave the biased error code
                 * in errno so that _if_ someone looks up the code somewhere,
                 * then it is at least the number that are usually listed.
                 */
                errno = WSAGetLastError();
                return -1;
        }
        /* convert into a file descriptor */
        if ((sockfd = _open_osfhandle(s, O_RDWR|O_BINARY)) < 0) {
                closesocket(s);
                return error("unable to make a socket file descriptor: %s",
                        strerror(errno));
        }
        return sockfd;
}

#undef connect
int mingw_connect(int sockfd, struct sockaddr *sa, size_t sz)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return connect(s, sa, sz);
}

#undef bind
int mingw_bind(int sockfd, struct sockaddr *sa, size_t sz)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return bind(s, sa, sz);
}

#undef setsockopt
int mingw_setsockopt(int sockfd, int lvl, int optname, void *optval, int optlen)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return setsockopt(s, lvl, optname, (const char*)optval, optlen);
}

#undef shutdown
int mingw_shutdown(int sockfd, int how)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return shutdown(s, how);
}

#undef listen
int mingw_listen(int sockfd, int backlog)
{
        SOCKET s = (SOCKET)_get_osfhandle(sockfd);
        return listen(s, backlog);
}

#undef accept
int mingw_accept(int sockfd1, struct sockaddr *sa, socklen_t *sz)
{
        int sockfd2;

        SOCKET s1 = (SOCKET)_get_osfhandle(sockfd1);
        SOCKET s2 = accept(s1, sa, sz);

        /* convert into a file descriptor */
        if ((sockfd2 = _open_osfhandle(s2, O_RDWR|O_BINARY)) < 0) {
                int err = errno;
                closesocket(s2);
                return error("unable to make a socket file descriptor: %s",
                        strerror(err));
        }
        return sockfd2;
}

#undef rename
int mingw_rename(const char *pold, const char *pnew)
{
        DWORD attrs, gle;
        int tries = 0;
        wchar_t wpold[MAX_PATH], wpnew[MAX_PATH];
        if (xutftowcs_path(wpold, pold) < 0 || xutftowcs_path(wpnew, pnew) < 0)
                return -1;

        /*
         * Try native rename() first to get errno right.
         * It is based on MoveFile(), which cannot overwrite existing files.
         */
        if (!_wrename(wpold, wpnew))
                return 0;
        if (errno != EEXIST)
                return -1;
repeat:
        if (MoveFileExW(wpold, wpnew, MOVEFILE_REPLACE_EXISTING))
                return 0;
        /* TODO: translate more errors */
        gle = GetLastError();
        if (gle == ERROR_ACCESS_DENIED &&
            (attrs = GetFileAttributesW(wpnew)) != INVALID_FILE_ATTRIBUTES) {
                if (attrs & FILE_ATTRIBUTE_DIRECTORY) {
                        DWORD attrsold = GetFileAttributesW(wpold);
                        if (attrsold == INVALID_FILE_ATTRIBUTES ||
                            !(attrsold & FILE_ATTRIBUTE_DIRECTORY))
                                errno = EISDIR;
                        else if (!_wrmdir(wpnew))
                                goto repeat;
                        return -1;
                }
                if ((attrs & FILE_ATTRIBUTE_READONLY) &&
                    SetFileAttributesW(wpnew, attrs & ~FILE_ATTRIBUTE_READONLY)) {
                        if (MoveFileExW(wpold, wpnew, MOVEFILE_REPLACE_EXISTING))
                                return 0;
                        gle = GetLastError();
                        /* revert file attributes on failure */
                        SetFileAttributesW(wpnew, attrs);
                }
        }
        if (tries < ARRAY_SIZE(delay) && gle == ERROR_ACCESS_DENIED) {
                /*
                 * We assume that some other process had the source or
                 * destination file open at the wrong moment and retry.
                 * In order to give the other process a higher chance to
                 * complete its operation, we give up our time slice now.
                 * If we have to retry again, we do sleep a bit.
                 */
                Sleep(delay[tries]);
                tries++;
                goto repeat;
        }
        if (gle == ERROR_ACCESS_DENIED &&
               ask_yes_no_if_possible("Rename from '%s' to '%s' failed. "
                       "Should I try again?", pold, pnew))
                goto repeat;

        errno = EACCES;
        return -1;
}

/*
 * Note that this doesn't return the actual pagesize, but
 * the allocation granularity. If future Windows specific git code
 * needs the real getpagesize function, we need to find another solution.
 */
int mingw_getpagesize(void)
{
        SYSTEM_INFO si;
        GetSystemInfo(&si);
        return si.dwAllocationGranularity;
}

/* See https://msdn.microsoft.com/en-us/library/windows/desktop/ms724435.aspx */
enum EXTENDED_NAME_FORMAT {
        NameDisplay = 3,
        NameUserPrincipal = 8
};

static char *get_extended_user_info(enum EXTENDED_NAME_FORMAT type)
{
        DECLARE_PROC_ADDR(secur32.dll, BOOL, GetUserNameExW,
                enum EXTENDED_NAME_FORMAT, LPCWSTR, PULONG);
        static wchar_t wbuffer[1024];
        DWORD len;

        if (!INIT_PROC_ADDR(GetUserNameExW))
                return NULL;

        len = ARRAY_SIZE(wbuffer);
        if (GetUserNameExW(type, wbuffer, &len)) {
                char *converted = xmalloc((len *= 3));
                if (xwcstoutf(converted, wbuffer, len) >= 0)
                        return converted;
                free(converted);
        }

        return NULL;
}

char *mingw_query_user_email(void)
{
        return get_extended_user_info(NameUserPrincipal);
}

struct passwd *getpwuid(int uid)
{
        static unsigned initialized;
        static char user_name[100];
        static struct passwd *p;
        wchar_t buf[100];
        DWORD len;

        if (initialized)
                return p;

        len = ARRAY_SIZE(buf);
        if (!GetUserNameW(buf, &len)) {
                initialized = 1;
                return NULL;
        }

        if (xwcstoutf(user_name, buf, sizeof(user_name)) < 0) {
                initialized = 1;
                return NULL;
        }

        p = xmalloc(sizeof(*p));
        p->pw_name = user_name;
        p->pw_gecos = get_extended_user_info(NameDisplay);
        if (!p->pw_gecos)
                p->pw_gecos = "unknown";
        p->pw_dir = NULL;

        initialized = 1;
        return p;
}

static HANDLE timer_event;
static HANDLE timer_thread;
static int timer_interval;
static int one_shot;
static sig_handler_t timer_fn = SIG_DFL, sigint_fn = SIG_DFL;

/* The timer works like this:
 * The thread, ticktack(), is a trivial routine that most of the time
 * only waits to receive the signal to terminate. The main thread tells
 * the thread to terminate by setting the timer_event to the signalled
 * state.
 * But ticktack() interrupts the wait state after the timer's interval
 * length to call the signal handler.
 */

static unsigned __stdcall ticktack(void *dummy)
{
        while (WaitForSingleObject(timer_event, timer_interval) == WAIT_TIMEOUT) {
                mingw_raise(SIGALRM);
                if (one_shot)
                        break;
        }
        return 0;
}

static int start_timer_thread(void)
{
        timer_event = CreateEvent(NULL, FALSE, FALSE, NULL);
        if (timer_event) {
                timer_thread = (HANDLE) _beginthreadex(NULL, 0, ticktack, NULL, 0, NULL);
                if (!timer_thread )
                        return errno = ENOMEM,
                                error("cannot start timer thread");
        } else
                return errno = ENOMEM,
                        error("cannot allocate resources for timer");
        return 0;
}

static void stop_timer_thread(void)
{
        if (timer_event)
                SetEvent(timer_event);  /* tell thread to terminate */
        if (timer_thread) {
                int rc = WaitForSingleObject(timer_thread, 10000);
                if (rc == WAIT_TIMEOUT)
                        error("timer thread did not terminate timely");
                else if (rc != WAIT_OBJECT_0)
                        error("waiting for timer thread failed: %lu",
                              GetLastError());
                CloseHandle(timer_thread);
        }
        if (timer_event)
                CloseHandle(timer_event);
        timer_event = NULL;
        timer_thread = NULL;
}

static inline int is_timeval_eq(const struct timeval *i1, const struct timeval *i2)
{
        return i1->tv_sec == i2->tv_sec && i1->tv_usec == i2->tv_usec;
}

int setitimer(int type, struct itimerval *in, struct itimerval *out)
{
        static const struct timeval zero;
        static int atexit_done;

        if (out != NULL)
                return errno = EINVAL,
                        error("setitimer param 3 != NULL not implemented");
        if (!is_timeval_eq(&in->it_interval, &zero) &&
            !is_timeval_eq(&in->it_interval, &in->it_value))
                return errno = EINVAL,
                        error("setitimer: it_interval must be zero or eq it_value");

        if (timer_thread)
                stop_timer_thread();

        if (is_timeval_eq(&in->it_value, &zero) &&
            is_timeval_eq(&in->it_interval, &zero))
                return 0;

        timer_interval = in->it_value.tv_sec * 1000 + in->it_value.tv_usec / 1000;
        one_shot = is_timeval_eq(&in->it_interval, &zero);
        if (!atexit_done) {
                atexit(stop_timer_thread);
                atexit_done = 1;
        }
        return start_timer_thread();
}

int sigaction(int sig, struct sigaction *in, struct sigaction *out)
{
        if (sig != SIGALRM)
                return errno = EINVAL,
                        error("sigaction only implemented for SIGALRM");
        if (out != NULL)
                return errno = EINVAL,
                        error("sigaction: param 3 != NULL not implemented");

        timer_fn = in->sa_handler;
        return 0;
}

#undef signal
sig_handler_t mingw_signal(int sig, sig_handler_t handler)
{
        sig_handler_t old;

        switch (sig) {
        case SIGALRM:
                old = timer_fn;
                timer_fn = handler;
                break;

        case SIGINT:
                old = sigint_fn;
                sigint_fn = handler;
                break;

        default:
                return signal(sig, handler);
        }

        return old;
}

#undef raise
int mingw_raise(int sig)
{
        switch (sig) {
        case SIGALRM:
                if (timer_fn == SIG_DFL) {
                        if (isatty(STDERR_FILENO))
                                fputs("Alarm clock\n", stderr);
                        exit(128 + SIGALRM);
                } else if (timer_fn != SIG_IGN)
                        timer_fn(SIGALRM);
                return 0;

        case SIGINT:
                if (sigint_fn == SIG_DFL)
                        exit(128 + SIGINT);
                else if (sigint_fn != SIG_IGN)
                        sigint_fn(SIGINT);
                return 0;

#if defined(_MSC_VER)
        case SIGILL:
        case SIGFPE:
        case SIGSEGV:
        case SIGTERM:
        case SIGBREAK:
        case SIGABRT:
        case SIGABRT_COMPAT:
                /*
                 * The <signal.h> header in the MS C Runtime defines 8 signals
                 * as being supported on the platform. Anything else causes an
                 * "Invalid signal or error" (which in DEBUG builds causes the
                 * Abort/Retry/Ignore dialog). We by-pass the CRT for things we
                 * already know will fail.
                 */
                return raise(sig);
        default:
                errno = EINVAL;
                return -1;

#else

        default:
                return raise(sig);

#endif

        }
}

int link(const char *oldpath, const char *newpath)
{
        wchar_t woldpath[MAX_PATH], wnewpath[MAX_PATH];
        if (xutftowcs_path(woldpath, oldpath) < 0 ||
                xutftowcs_path(wnewpath, newpath) < 0)
                return -1;

        if (!CreateHardLinkW(wnewpath, woldpath, NULL)) {
                errno = err_win_to_posix(GetLastError());
                return -1;
        }
        return 0;
}

pid_t waitpid(pid_t pid, int *status, int options)
{
        HANDLE h = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION,
            FALSE, pid);
        if (!h) {
                errno = ECHILD;
                return -1;
        }

        if (pid > 0 && options & WNOHANG) {
                if (WAIT_OBJECT_0 != WaitForSingleObject(h, 0)) {
                        CloseHandle(h);
                        return 0;
                }
                options &= ~WNOHANG;
        }

        if (options == 0) {
                struct pinfo_t **ppinfo;
                if (WaitForSingleObject(h, INFINITE) != WAIT_OBJECT_0) {
                        CloseHandle(h);
                        return 0;
                }

                if (status)
                        GetExitCodeProcess(h, (LPDWORD)status);

                EnterCriticalSection(&pinfo_cs);

                ppinfo = &pinfo;
                while (*ppinfo) {
                        struct pinfo_t *info = *ppinfo;
                        if (info->pid == pid) {
                                CloseHandle(info->proc);
                                *ppinfo = info->next;
                                free(info);
                                break;
                        }
                        ppinfo = &info->next;
                }

                LeaveCriticalSection(&pinfo_cs);

                CloseHandle(h);
                return pid;
        }
        CloseHandle(h);

        errno = EINVAL;
        return -1;
}

int xutftowcsn(wchar_t *wcs, const char *utfs, size_t wcslen, int utflen)
{
        int upos = 0, wpos = 0;
        const unsigned char *utf = (const unsigned char*) utfs;
        if (!utf || !wcs || wcslen < 1) {
                errno = EINVAL;
                return -1;
        }
        /* reserve space for \0 */
        wcslen--;
        if (utflen < 0)
                utflen = INT_MAX;

        while (upos < utflen) {
                int c = utf[upos++] & 0xff;
                if (utflen == INT_MAX && c == 0)
                        break;

                if (wpos >= wcslen) {
                        wcs[wpos] = 0;
                        errno = ERANGE;
                        return -1;
                }

                if (c < 0x80) {
                        /* ASCII */
                        wcs[wpos++] = c;
                } else if (c >= 0xc2 && c < 0xe0 && upos < utflen &&
                                (utf[upos] & 0xc0) == 0x80) {
                        /* 2-byte utf-8 */
                        c = ((c & 0x1f) << 6);
                        c |= (utf[upos++] & 0x3f);
                        wcs[wpos++] = c;
                } else if (c >= 0xe0 && c < 0xf0 && upos + 1 < utflen &&
                                !(c == 0xe0 && utf[upos] < 0xa0) && /* over-long encoding */
                                (utf[upos] & 0xc0) == 0x80 &&
                                (utf[upos + 1] & 0xc0) == 0x80) {
                        /* 3-byte utf-8 */
                        c = ((c & 0x0f) << 12);
                        c |= ((utf[upos++] & 0x3f) << 6);
                        c |= (utf[upos++] & 0x3f);
                        wcs[wpos++] = c;
                } else if (c >= 0xf0 && c < 0xf5 && upos + 2 < utflen &&
                                wpos + 1 < wcslen &&
                                !(c == 0xf0 && utf[upos] < 0x90) && /* over-long encoding */
                                !(c == 0xf4 && utf[upos] >= 0x90) && /* > \u10ffff */
                                (utf[upos] & 0xc0) == 0x80 &&
                                (utf[upos + 1] & 0xc0) == 0x80 &&
                                (utf[upos + 2] & 0xc0) == 0x80) {
                        /* 4-byte utf-8: convert to \ud8xx \udcxx surrogate pair */
                        c = ((c & 0x07) << 18);
                        c |= ((utf[upos++] & 0x3f) << 12);
                        c |= ((utf[upos++] & 0x3f) << 6);
                        c |= (utf[upos++] & 0x3f);
                        c -= 0x10000;
                        wcs[wpos++] = 0xd800 | (c >> 10);
                        wcs[wpos++] = 0xdc00 | (c & 0x3ff);
                } else if (c >= 0xa0) {
                        /* invalid utf-8 byte, printable unicode char: convert 1:1 */
                        wcs[wpos++] = c;
                } else {
                        /* invalid utf-8 byte, non-printable unicode: convert to hex */
                        static const char *hex = "0123456789abcdef";
                        wcs[wpos++] = hex[c >> 4];
                        if (wpos < wcslen)
                                wcs[wpos++] = hex[c & 0x0f];
                }
        }
        wcs[wpos] = 0;
        return wpos;
}

int xwcstoutf(char *utf, const wchar_t *wcs, size_t utflen)
{
        if (!wcs || !utf || utflen < 1) {
                errno = EINVAL;
                return -1;
        }
        utflen = WideCharToMultiByte(CP_UTF8, 0, wcs, -1, utf, utflen, NULL, NULL);
        if (utflen)
                return utflen - 1;
        errno = ERANGE;
        return -1;
}

static void setup_windows_environment(void)
{
        char *tmp = getenv("TMPDIR");

        /* on Windows it is TMP and TEMP */
        if (!tmp) {
                if (!(tmp = getenv("TMP")))
                        tmp = getenv("TEMP");
                if (tmp) {
                        setenv("TMPDIR", tmp, 1);
                        tmp = getenv("TMPDIR");
                }
        }

        if (tmp) {
                /*
                 * Convert all dir separators to forward slashes,
                 * to help shell commands called from the Git
                 * executable (by not mistaking the dir separators
                 * for escape characters).
                 */
                convert_slashes(tmp);
        }

        /* simulate TERM to enable auto-color (see color.c) */
        if (!getenv("TERM"))
                setenv("TERM", "cygwin", 1);

        /* calculate HOME if not set */
        if (!getenv("HOME")) {
                /*
                 * try $HOMEDRIVE$HOMEPATH - the home share may be a network
                 * location, thus also check if the path exists (i.e. is not
                 * disconnected)
                 */
                if ((tmp = getenv("HOMEDRIVE"))) {
                        struct strbuf buf = STRBUF_INIT;
                        strbuf_addstr(&buf, tmp);
                        if ((tmp = getenv("HOMEPATH"))) {
                                strbuf_addstr(&buf, tmp);
                                if (is_directory(buf.buf))
                                        setenv("HOME", buf.buf, 1);
                                else
                                        tmp = NULL; /* use $USERPROFILE */
                        }
                        strbuf_release(&buf);
                }
                /* use $USERPROFILE if the home share is not available */
                if (!tmp && (tmp = getenv("USERPROFILE")))
                        setenv("HOME", tmp, 1);
        }
}

int is_valid_win32_path(const char *path, int allow_literal_nul)
{
        const char *p = path;
        int preceding_space_or_period = 0, i = 0, periods = 0;

        if (!protect_ntfs)
                return 1;

        skip_dos_drive_prefix((char **)&path);
        goto segment_start;

        for (;;) {
                char c = *(path++);
                switch (c) {
                case '\0':
                case '/': case '\\':
                        /* cannot end in ` ` or `.`, except for `.` and `..` */
                        if (preceding_space_or_period &&
                            (i != periods || periods > 2))
                                return 0;
                        if (!c)
                                return 1;

                        i = periods = preceding_space_or_period = 0;

segment_start:
                        switch (*path) {
                        case 'a': case 'A': /* AUX */
                                if (((c = path[++i]) != 'u' && c != 'U') ||
                                    ((c = path[++i]) != 'x' && c != 'X')) {
not_a_reserved_name:
                                        path += i;
                                        continue;
                                }
                                break;
                        case 'c': case 'C':
                                /* COM1 ... COM9, CON, CONIN$, CONOUT$ */
                                if ((c = path[++i]) != 'o' && c != 'O')
                                        goto not_a_reserved_name;
                                c = path[++i];
                                if (c == 'm' || c == 'M') { /* COM1 ... COM9 */
                                        c = path[++i];
                                        if (c < '1' || c > '9')
                                                goto not_a_reserved_name;
                                } else if (c == 'n' || c == 'N') { /* CON */
                                        c = path[i + 1];
                                        if ((c == 'i' || c == 'I') &&
                                            ((c = path[i + 2]) == 'n' ||
                                             c == 'N') &&
                                            path[i + 3] == '$')
                                                i += 3; /* CONIN$ */
                                        else if ((c == 'o' || c == 'O') &&
                                                 ((c = path[i + 2]) == 'u' ||
                                                  c == 'U') &&
                                                 ((c = path[i + 3]) == 't' ||
                                                  c == 'T') &&
                                                 path[i + 4] == '$')
                                                i += 4; /* CONOUT$ */
                                } else
                                        goto not_a_reserved_name;
                                break;
                        case 'l': case 'L': /* LPT<N> */
                                if (((c = path[++i]) != 'p' && c != 'P') ||
                                    ((c = path[++i]) != 't' && c != 'T') ||
                                    !isdigit(path[++i]))
                                        goto not_a_reserved_name;
                                break;
                        case 'n': case 'N': /* NUL */
                                if (((c = path[++i]) != 'u' && c != 'U') ||
                                    ((c = path[++i]) != 'l' && c != 'L') ||
                                    (allow_literal_nul &&
                                     !path[i + 1] && p == path))
                                        goto not_a_reserved_name;
                                break;
                        case 'p': case 'P': /* PRN */
                                if (((c = path[++i]) != 'r' && c != 'R') ||
                                    ((c = path[++i]) != 'n' && c != 'N'))
                                        goto not_a_reserved_name;
                                break;
                        default:
                                continue;
                        }

                        /*
                         * So far, this looks like a reserved name. Let's see
                         * whether it actually is one: trailing spaces, a file
                         * extension, or an NTFS Alternate Data Stream do not
                         * matter, the name is still reserved if any of those
                         * follow immediately after the actual name.
                         */
                        i++;
                        if (path[i] == ' ') {
                                preceding_space_or_period = 1;
                                while (path[++i] == ' ')
                                        ; /* skip all spaces */
                        }

                        c = path[i];
                        if (c && c != '.' && c != ':' && c != '/' && c != '\\')
                                goto not_a_reserved_name;

                        /* contains reserved name */
                        return 0;
                case '.':
                        periods++;
                        /* fallthru */
                case ' ':
                        preceding_space_or_period = 1;
                        i++;
                        continue;
                case ':': /* DOS drive prefix was already skipped */
                case '<': case '>': case '"': case '|': case '?': case '*':
                        /* illegal character */
                        return 0;
                default:
                        if (c > '\0' && c < '\x20')
                                /* illegal character */
                                return 0;
                }
                preceding_space_or_period = 0;
                i++;
        }
}

#if !defined(_MSC_VER)
/*
 * Disable MSVCRT command line wildcard expansion (__getmainargs called from
 * mingw startup code, see init.c in mingw runtime).
 */
int _CRT_glob = 0;
#endif

static NORETURN void die_startup(void)
{
        fputs("fatal: not enough memory for initialization", stderr);
        exit(128);
}

static void *malloc_startup(size_t size)
{
        void *result = malloc(size);
        if (!result)
                die_startup();
        return result;
}

static char *wcstoutfdup_startup(char *buffer, const wchar_t *wcs, size_t len)
{
        len = xwcstoutf(buffer, wcs, len) + 1;
        return memcpy(malloc_startup(len), buffer, len);
}

static void maybe_redirect_std_handle(const wchar_t *key, DWORD std_id, int fd,
                                      DWORD desired_access, DWORD flags)
{
        DWORD create_flag = fd ? OPEN_ALWAYS : OPEN_EXISTING;
        wchar_t buf[MAX_PATH];
        DWORD max = ARRAY_SIZE(buf);
        HANDLE handle;
        DWORD ret = GetEnvironmentVariableW(key, buf, max);

        if (!ret || ret >= max)
                return;

        /* make sure this does not leak into child processes */
        SetEnvironmentVariableW(key, NULL);
        if (!wcscmp(buf, L"off")) {
                close(fd);
                handle = GetStdHandle(std_id);
                if (handle != INVALID_HANDLE_VALUE)
                        CloseHandle(handle);
                return;
        }
        if (std_id == STD_ERROR_HANDLE && !wcscmp(buf, L"2>&1")) {
                handle = GetStdHandle(STD_OUTPUT_HANDLE);
                if (handle == INVALID_HANDLE_VALUE) {
                        close(fd);
                        handle = GetStdHandle(std_id);
                        if (handle != INVALID_HANDLE_VALUE)
                                CloseHandle(handle);
                } else {
                        int new_fd = _open_osfhandle((intptr_t)handle, O_BINARY);
                        SetStdHandle(std_id, handle);
                        dup2(new_fd, fd);
                        /* do *not* close the new_fd: that would close stdout */
                }
                return;
        }
        handle = CreateFileW(buf, desired_access, 0, NULL, create_flag,
                             flags, NULL);
        if (handle != INVALID_HANDLE_VALUE) {
                int new_fd = _open_osfhandle((intptr_t)handle, O_BINARY);
                SetStdHandle(std_id, handle);
                dup2(new_fd, fd);
                close(new_fd);
        }
}

static void maybe_redirect_std_handles(void)
{
        maybe_redirect_std_handle(L"GIT_REDIRECT_STDIN", STD_INPUT_HANDLE, 0,
                                  GENERIC_READ, FILE_ATTRIBUTE_NORMAL);
        maybe_redirect_std_handle(L"GIT_REDIRECT_STDOUT", STD_OUTPUT_HANDLE, 1,
                                  GENERIC_WRITE, FILE_ATTRIBUTE_NORMAL);
        maybe_redirect_std_handle(L"GIT_REDIRECT_STDERR", STD_ERROR_HANDLE, 2,
                                  GENERIC_WRITE, FILE_FLAG_NO_BUFFERING);
}

#ifdef _MSC_VER
#ifdef _DEBUG
#include <crtdbg.h>
#endif
#endif

/*
 * We implement wmain() and compile with -municode, which would
 * normally ignore main(), but we call the latter from the former
 * so that we can handle non-ASCII command-line parameters
 * appropriately.
 *
 * To be more compatible with the core git code, we convert
 * argv into UTF8 and pass them directly to main().
 */
int wmain(int argc, const wchar_t **wargv)
{
        int i, maxlen, exit_status;
        char *buffer, **save;
        const char **argv;

        trace2_initialize_clock();

#ifdef _MSC_VER
#ifdef _DEBUG
        _CrtSetReportMode(_CRT_ASSERT, _CRTDBG_MODE_DEBUG);
#endif

#ifdef USE_MSVC_CRTDBG
        _CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
#endif
#endif

        maybe_redirect_std_handles();

        /* determine size of argv and environ conversion buffer */
        maxlen = wcslen(wargv[0]);
        for (i = 1; i < argc; i++)
                maxlen = max(maxlen, wcslen(wargv[i]));

        /* allocate buffer (wchar_t encodes to max 3 UTF-8 bytes) */
        maxlen = 3 * maxlen + 1;
        buffer = malloc_startup(maxlen);

        /*
         * Create a UTF-8 version of w_argv. Also create a "save" copy
         * to remember all the string pointers because parse_options()
         * will remove claimed items from the argv that we pass down.
         */
        ALLOC_ARRAY(argv, argc + 1);
        ALLOC_ARRAY(save, argc + 1);
        for (i = 0; i < argc; i++)
                argv[i] = save[i] = wcstoutfdup_startup(buffer, wargv[i], maxlen);
        argv[i] = save[i] = NULL;
        free(buffer);

        /* fix Windows specific environment settings */
        setup_windows_environment();

        unset_environment_variables = xstrdup("PERL5LIB");

        /* initialize critical section for waitpid pinfo_t list */
        InitializeCriticalSection(&pinfo_cs);

        /* set up default file mode and file modes for stdin/out/err */
        _fmode = _O_BINARY;
        _setmode(_fileno(stdin), _O_BINARY);
        _setmode(_fileno(stdout), _O_BINARY);
        _setmode(_fileno(stderr), _O_BINARY);

        /* initialize Unicode console */
        winansi_init();

        /* invoke the real main() using our utf8 version of argv. */
        exit_status = main(argc, argv);

        for (i = 0; i < argc; i++)
                free(save[i]);
        free(save);
        free(argv);

        return exit_status;
}

int uname(struct utsname *buf)
{
        unsigned v = (unsigned)GetVersion();
        memset(buf, 0, sizeof(*buf));
        xsnprintf(buf->sysname, sizeof(buf->sysname), "Windows");
        xsnprintf(buf->release, sizeof(buf->release),
                 "%u.%u", v & 0xff, (v >> 8) & 0xff);
        /* assuming NT variants only.. */
        xsnprintf(buf->version, sizeof(buf->version),
                  "%u", (v >> 16) & 0x7fff);
        return 0;
}