diff options
Diffstat (limited to 'compat/mingw.c')
| -rw-r--r-- | compat/mingw.c | 76 |
1 files changed, 71 insertions, 5 deletions
diff --git a/compat/mingw.c b/compat/mingw.c index a67872babf..18caf21969 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -341,12 +341,74 @@ int mingw_mkdir(const char *path, int mode) 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; wchar_t wfilename[MAX_PATH]; + open_fn_t open_fn; va_start(args, oflags); mode = va_arg(args, int); @@ -355,9 +417,14 @@ int mingw_open (const char *filename, int oflags, ...) if (filename && !strcmp(filename, "/dev/null")) filename = "nul"; + if ((oflags & O_APPEND) && !is_local_named_pipe_path(filename)) + open_fn = mingw_open_append; + else + open_fn = _wopen; + if (xutftowcs_path(wfilename, filename) < 0) return -1; - fd = _wopen(wfilename, oflags, mode); + fd = open_fn(wfilename, oflags, mode); if (fd < 0 && (oflags & O_ACCMODE) != O_RDONLY && errno == EACCES) { DWORD attrs = GetFileAttributesW(wfilename); @@ -375,7 +442,7 @@ int mingw_open (const char *filename, int oflags, ...) * CREATE_ALWAYS flag of CreateFile()). */ if (fd < 0 && errno == EACCES) - fd = _wopen(wfilename, oflags & ~O_CREAT, mode); + fd = open_fn(wfilename, oflags & ~O_CREAT, mode); if (fd >= 0 && set_hidden_flag(wfilename, 1)) warning("could not mark '%s' as hidden.", filename); } @@ -2221,7 +2288,7 @@ void mingw_startup(void) die_startup(); /* determine size of argv and environ conversion buffer */ - maxlen = wcslen(_wpgmptr); + maxlen = wcslen(wargv[0]); for (i = 1; i < argc; i++) maxlen = max(maxlen, wcslen(wargv[i])); for (i = 0; wenv[i]; i++) @@ -2241,8 +2308,7 @@ void mingw_startup(void) buffer = malloc_startup(maxlen); /* convert command line arguments and environment to UTF-8 */ - __argv[0] = wcstoutfdup_startup(buffer, _wpgmptr, maxlen); - for (i = 1; i < argc; i++) + for (i = 0; i < argc; i++) __argv[i] = wcstoutfdup_startup(buffer, wargv[i], maxlen); for (i = 0; wenv[i]; i++) environ[i] = wcstoutfdup_startup(buffer, wenv[i], maxlen); |