diff --git a/compat/mingw.c b/compat/mingw.c index e326c6fcd2..0d9600543c 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -532,6 +532,70 @@ static int mingw_open_append(wchar_t const *wfilename, int oflags, ...) return fd; } +/* + * Ideally, we'd use `_wopen()` to implement this functionality so that we + * don't have to reimplement it, but unfortunately we do not have tight control + * over the share mode there. And while `_wsopen()` and friends exist that give + * us _some_ control over the share mode, this family of functions doesn't give + * us the ability to enable FILE_SHARE_DELETE, either. But this is a strict + * requirement for us though so that we can unlink or rename over files that + * are held open by another process. + * + * We are thus forced to implement our own emulation of `open()`. To make our + * life simpler we only implement basic support for this, namely opening + * existing files for reading and/or writing. This means that newly created + * files won't have their sharing mode set up correctly, but for now I couldn't + * find any case where this matters. We may have to revisit that in the future + * though based on our needs. + */ +static int mingw_open_existing(const wchar_t *filename, int oflags, ...) +{ + SECURITY_ATTRIBUTES security_attributes = { + .nLength = sizeof(security_attributes), + .bInheritHandle = !(oflags & O_NOINHERIT), + }; + HANDLE handle; + DWORD access; + int fd; + + /* We only support basic flags. */ + if (oflags & ~(O_ACCMODE | O_NOINHERIT)) { + errno = ENOSYS; + return -1; + } + + switch (oflags & O_ACCMODE) { + case O_RDWR: + access = GENERIC_READ | GENERIC_WRITE; + break; + case O_WRONLY: + access = GENERIC_WRITE; + break; + default: + access = GENERIC_READ; + break; + } + + handle = CreateFileW(filename, access, + FILE_SHARE_WRITE | FILE_SHARE_READ | FILE_SHARE_DELETE, + &security_attributes, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); + if (handle == INVALID_HANDLE_VALUE) { + DWORD err = GetLastError(); + + /* See `mingw_open_append()` for why we have this conversion. */ + if (err == ERROR_INVALID_PARAMETER) + err = ERROR_PATH_NOT_FOUND; + + errno = err_win_to_posix(err); + return -1; + } + + fd = _open_osfhandle((intptr_t)handle, oflags | 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? @@ -567,6 +631,8 @@ int mingw_open (const char *filename, int oflags, ...) if ((oflags & O_APPEND) && !is_local_named_pipe_path(filename)) open_fn = mingw_open_append; + else if (!(oflags & ~(O_ACCMODE | O_NOINHERIT))) + open_fn = mingw_open_existing; else open_fn = _wopen;