From: Johannes Sixt <j6t@kdbg•org>
To: Johannes Schindelin <johannes.schindelin@gmx•de>
Cc: Karsten Blees via GitGitGadget <gitgitgadget@gmail•com>,
git@vger•kernel.org
Subject: Re: [PATCH 11/18] mingw: support renaming symlinks
Date: Thu, 18 Dec 2025 18:44:37 +0100 [thread overview]
Message-ID: <02fa15af-5a57-4557-b016-fd14b9107c6e@kdbg.org> (raw)
In-Reply-To: <5cb3b10500339fec403b84e30721e4f6a68e42f6.1765980535.git.gitgitgadget@gmail.com>
Am 17.12.25 um 15:08 schrieb Karsten Blees via GitGitGadget:
> From: Karsten Blees <blees@dcon•de>
>
> Older MSVCRT's `_wrename()` function cannot rename symlinks over
> existing files: it returns success without doing anything. Newer
> MSVCR*.dll versions probably do not share this problem: according to CRT
> sources, they just call `MoveFileEx()` with the `MOVEFILE_COPY_ALLOWED`
> flag.
>
> Avoid the `_wrename()` call, and go with directly calling
> `MoveFileEx()`, with proper error handling of course.
>
> Signed-off-by: Karsten Blees <blees@dcon•de>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx•de>
> ---
> compat/mingw.c | 38 ++++++++++++++++----------------------
> 1 file changed, 16 insertions(+), 22 deletions(-)
>
> diff --git a/compat/mingw.c b/compat/mingw.c
> index b1cc30d0f1..55f0bb478e 100644
> --- a/compat/mingw.c
> +++ b/compat/mingw.c
> @@ -2275,7 +2275,7 @@ int mingw_accept(int sockfd1, struct sockaddr *sa, socklen_t *sz)
> int mingw_rename(const char *pold, const char *pnew)
> {
> static int supports_file_rename_info_ex = 1;
> - DWORD attrs, gle;
> + DWORD attrs = INVALID_FILE_ATTRIBUTES, gle;
> int tries = 0;
> wchar_t wpold[MAX_PATH], wpnew[MAX_PATH];
> int wpnew_len;
> @@ -2286,15 +2286,6 @@ int mingw_rename(const char *pold, const char *pnew)
> if (wpnew_len < 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 (supports_file_rename_info_ex) {
> /*
> @@ -2370,13 +2361,22 @@ repeat:
> * to retry.
> */
> } else {
> - if (MoveFileExW(wpold, wpnew, MOVEFILE_REPLACE_EXISTING))
> + if (MoveFileExW(wpold, wpnew,
> + MOVEFILE_REPLACE_EXISTING | MOVEFILE_COPY_ALLOWED))
> return 0;
> gle = GetLastError();
> }
>
> - /* TODO: translate more errors */
> - if (gle == ERROR_ACCESS_DENIED &&
> + /* revert file attributes on failure */
> + if (attrs != INVALID_FILE_ATTRIBUTES)
> + SetFileAttributesW(wpnew, attrs);
> +
> + if (!is_file_in_use_error(gle)) {
> + errno = err_win_to_posix(gle);
> + return -1;
> + }
> +
> + if (attrs == INVALID_FILE_ATTRIBUTES &&
> (attrs = GetFileAttributesW(wpnew)) != INVALID_FILE_ATTRIBUTES) {
> if (attrs & FILE_ATTRIBUTE_DIRECTORY) {
> DWORD attrsold = GetFileAttributesW(wpold);
> @@ -2388,16 +2388,10 @@ 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);
> - }
> + SetFileAttributesW(wpnew, attrs & ~FILE_ATTRIBUTE_READONLY))
> + goto repeat;
> }
> - if (gle == ERROR_ACCESS_DENIED &&
> - retry_ask_yes_no(&tries, "Rename from '%s' to '%s' failed. "
> + if (retry_ask_yes_no(&tries, "Rename from '%s' to '%s' failed. "
> "Should I try again?", pold, pnew))
> goto repeat;
>
The logic in this function is incredibly convoluted. It does look
somewhat reasonable, at least on the non-error path, but whether the
variable attr is changed and reset as needed after 'goto repeat' and the
various failure modes, I cannot tell. I give up and trust that this code
has been battle-tested during the past decade and works as desired.
-- Hannes
next prev parent reply other threads:[~2025-12-18 17:44 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-12-17 14:08 [PATCH 00/18] Support symbolic links on Windows Johannes Schindelin via GitGitGadget
2025-12-17 14:08 ` [PATCH 01/18] mingw: don't call `GetFileAttributes()` twice in `mingw_lstat()` Karsten Blees via GitGitGadget
2025-12-18 10:34 ` Johannes Sixt
2025-12-17 14:08 ` [PATCH 02/18] mingw: implement `stat()` with symlink support Karsten Blees via GitGitGadget
2025-12-18 10:44 ` Johannes Sixt
2026-01-09 20:04 ` Johannes Schindelin
2025-12-17 14:08 ` [PATCH 03/18] mingw: drop the separate `do_lstat()` function Karsten Blees via GitGitGadget
2025-12-18 10:48 ` Johannes Sixt
2025-12-17 14:08 ` [PATCH 04/18] mingw: let `mingw_lstat()` error early upon problems with reparse points Karsten Blees via GitGitGadget
2025-12-17 14:08 ` [PATCH 05/18] mingw: teach dirent about symlinks Karsten Blees via GitGitGadget
2025-12-17 14:08 ` [PATCH 06/18] mingw: compute the correct size for symlinks in `mingw_lstat()` Bill Zissimopoulos via GitGitGadget
2025-12-17 14:08 ` [PATCH 07/18] mingw: factor out the retry logic Karsten Blees via GitGitGadget
2025-12-17 14:08 ` [PATCH 08/18] mingw: change default of `core.symlinks` to false Karsten Blees via GitGitGadget
2025-12-17 14:08 ` [PATCH 09/18] mingw: add symlink-specific error codes Karsten Blees via GitGitGadget
2025-12-17 14:08 ` [PATCH 10/18] mingw: handle symlinks to directories in `mingw_unlink()` Karsten Blees via GitGitGadget
2025-12-18 2:49 ` Ben Knoble
2026-01-09 20:04 ` Johannes Schindelin
2025-12-17 14:08 ` [PATCH 11/18] mingw: support renaming symlinks Karsten Blees via GitGitGadget
2025-12-18 17:44 ` Johannes Sixt [this message]
2026-01-09 20:04 ` Johannes Schindelin
2025-12-17 14:08 ` [PATCH 12/18] mingw: allow `mingw_chdir()` to change to symlink-resolved directories Karsten Blees via GitGitGadget
2025-12-17 14:08 ` [PATCH 13/18] mingw: implement `readlink()` Karsten Blees via GitGitGadget
2025-12-18 18:13 ` Johannes Sixt
2026-01-09 20:04 ` Johannes Schindelin
2025-12-17 14:08 ` [PATCH 14/18] mingw: implement basic `symlink()` functionality (file symlinks only) Karsten Blees via GitGitGadget
2025-12-17 14:08 ` [PATCH 15/18] mingw: add support for symlinks to directories Karsten Blees via GitGitGadget
2025-12-17 14:08 ` [PATCH 16/18] mingw: try to create symlinks without elevated permissions Johannes Schindelin via GitGitGadget
2025-12-17 14:08 ` [PATCH 17/18] mingw: emulate `stat()` a little more faithfully Johannes Schindelin via GitGitGadget
2025-12-17 14:08 ` [PATCH 18/18] mingw: special-case index entries for symlinks with buggy size Johannes Schindelin via GitGitGadget
2025-12-18 0:00 ` [PATCH 00/18] Support symbolic links on Windows Junio C Hamano
2025-12-18 18:51 ` Johannes Sixt
2025-12-18 19:33 ` Karsten Blees
2026-01-09 20:04 ` [PATCH v2 " Johannes Schindelin via GitGitGadget
2026-01-09 20:04 ` [PATCH v2 01/18] mingw: don't call `GetFileAttributes()` twice in `mingw_lstat()` Karsten Blees via GitGitGadget
2026-01-09 20:04 ` [PATCH v2 02/18] mingw: implement `stat()` with symlink support Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 03/18] mingw: drop the separate `do_lstat()` function Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 04/18] mingw: let `mingw_lstat()` error early upon problems with reparse points Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 05/18] mingw: teach dirent about symlinks Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 06/18] mingw: compute the correct size for symlinks in `mingw_lstat()` Bill Zissimopoulos via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 07/18] mingw: factor out the retry logic Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 08/18] mingw: change default of `core.symlinks` to false Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 09/18] mingw: add symlink-specific error codes Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 10/18] mingw: handle symlinks to directories in `mingw_unlink()` Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 11/18] mingw: support renaming symlinks Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 12/18] mingw: allow `mingw_chdir()` to change to symlink-resolved directories Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 13/18] mingw: implement `readlink()` Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 14/18] mingw: implement basic `symlink()` functionality (file symlinks only) Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 15/18] mingw: add support for symlinks to directories Karsten Blees via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 16/18] mingw: try to create symlinks without elevated permissions Johannes Schindelin via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 17/18] mingw: emulate `stat()` a little more faithfully Johannes Schindelin via GitGitGadget
2026-01-09 20:05 ` [PATCH v2 18/18] mingw: special-case index entries for symlinks with buggy size Johannes Schindelin via GitGitGadget
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