From: Junio C Hamano <gitster@pobox•com>
To: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail•com>
Cc: git@vger•kernel.org, Johannes Schindelin <johannes.schindelin@gmx•de>
Subject: Re: [PATCH 03/10] mingw: special-case `open(symlink, O_CREAT | O_EXCL)`
Date: Sat, 29 Nov 2025 22:49:22 -0800 [thread overview]
Message-ID: <xmqqecpgc8wd.fsf@gitster.g> (raw)
In-Reply-To: <96e279f50ebc26084095e781cf58db233fa05b74.1764440906.git.gitgitgadget@gmail.com> (Johannes Schindelin via GitGitGadget's message of "Sat, 29 Nov 2025 18:28:19 +0000")
"Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail•com>
writes:
> From: Johannes Schindelin <johannes.schindelin@gmx•de>
>
> The `_wopen()` function would gladly follow a symbolic link to a
> non-existent file and create it when given above-mentioned flags.
>
> Git expects the `open()` call to fail, though. So let's add yet another
> work-around to pretend that Windows behaves like Linux.
"like Linux" -> "as POSIX expects"?
cf. https://pubs.opengroup.org/onlinepubs/007904875/functions/open.html#:~:text=If%20O_CREAT%20and%20O_EXCL%20are,set%2C%20the%20result%20is%20undefined.
> This is required to let t4115.8(--reject removes .rej symlink if it
> exists) pass on Windows when enabling the MSYS2 runtime's symbolic link
> support.
>
> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx•de>
> ---
> compat/mingw.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/compat/mingw.c b/compat/mingw.c
> index 736a07a028..9fbf12a3d3 100644
> --- a/compat/mingw.c
> +++ b/compat/mingw.c
> @@ -627,6 +627,7 @@ int mingw_open (const char *filename, int oflags, ...)
> int fd, create = (oflags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL);
> wchar_t wfilename[MAX_PATH];
> open_fn_t open_fn;
> + WIN32_FILE_ATTRIBUTE_DATA fdata;
>
> DECLARE_PROC_ADDR(ntdll.dll, NTSTATUS, NTAPI, RtlGetLastNtStatus, void);
>
> @@ -651,6 +652,19 @@ int mingw_open (const char *filename, int oflags, ...)
> else if (xutftowcs_path(wfilename, filename) < 0)
> return -1;
>
> + /*
> + * When `symlink` exists and is a symbolic link pointing to a
> + * non-existing file, `_wopen(symlink, O_CREAT | O_EXCL)` would
> + * create that file. Not what we want: Linux would say `EEXIST`
> + * in that instance, which is therefore what Git expects.
> + */
"Linux" -> "open() on POSIX-compliant systems".
IOW, _wopen() does not have to behave like POSIX open() and the compat/
layer is how the emulation goes.
FWIW, this is not limited to symbolic links but anything that exists
at the path specified should cause the same EEXIST failure. The
O_CREAT|O_EXCL combination asks the system to atomically create the
thing anew (or fail).
O_EXCL
If O_CREAT and O_EXCL are set, open() shall fail if the file
exists. The check for the existence of the file and the creation of
the file if it does not exist shall be atomic with respect to other
threads executing open() naming the same filename in the same
directory with O_EXCL and O_CREAT set. If O_EXCL and O_CREAT are
set, and path names a symbolic link, open() shall fail and set errno
to [EEXIST], regardless of the contents of the symbolic link. If
O_EXCL is set and O_CREAT is not set, the result is undefined.
> + if (create &&
> + GetFileAttributesExW(wfilename, GetFileExInfoStandard, &fdata) &&
> + (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT)) {
> + errno = EEXIST;
> + return -1;
> + }
> +
> fd = open_fn(wfilename, oflags, mode);
>
> /*
next prev parent reply other threads:[~2025-11-30 6:49 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-29 18:28 [PATCH 00/10] Prepare Git's test suite for symbolic link support on Windows Johannes Schindelin via GitGitGadget
2025-11-29 18:28 ` [PATCH 01/10] t9700: accommodate for Windows paths Johannes Schindelin via GitGitGadget
2025-11-29 18:28 ` [PATCH 02/10] apply: symbolic links lack a "trustable executable bit" Johannes Schindelin via GitGitGadget
2025-11-29 18:28 ` [PATCH 03/10] mingw: special-case `open(symlink, O_CREAT | O_EXCL)` Johannes Schindelin via GitGitGadget
2025-11-30 6:49 ` Junio C Hamano [this message]
2025-12-01 13:18 ` Johannes Schindelin
2025-12-06 2:17 ` Junio C Hamano
2025-11-29 18:28 ` [PATCH 04/10] t0001: handle `diff --no-index` gracefully Johannes Schindelin via GitGitGadget
2025-11-30 5:59 ` Junio C Hamano
2025-12-01 13:20 ` Johannes Schindelin
2025-12-02 8:15 ` Junio C Hamano
2025-11-29 18:28 ` [PATCH 05/10] t0301: another fix for Windows compatibility Johannes Schindelin via GitGitGadget
2025-11-30 6:09 ` Junio C Hamano
2025-12-01 13:25 ` Johannes Schindelin
2025-12-02 8:15 ` Junio C Hamano
2025-12-02 11:14 ` Johannes Schindelin
2025-12-06 1:05 ` Junio C Hamano
2025-11-29 18:28 ` [PATCH 06/10] t0600: fix incomplete prerequisite for a test case Johannes Schindelin via GitGitGadget
2025-12-01 9:46 ` Patrick Steinhardt
2025-12-01 13:27 ` Johannes Schindelin
2025-11-29 18:28 ` [PATCH 07/10] t1006: accommodate for symlink support in MSYS2 Johannes Schindelin via GitGitGadget
2025-12-01 9:47 ` Patrick Steinhardt
2025-12-01 13:29 ` Johannes Schindelin
2025-12-01 13:34 ` Patrick Steinhardt
2025-11-29 18:28 ` [PATCH 08/10] t1305: skip symlink tests that do not apply to Windows Johannes Schindelin via GitGitGadget
2025-11-29 18:28 ` [PATCH 09/10] t6423: introduce Windows-specific handling for symlinking to /dev/null Johannes Schindelin via GitGitGadget
2025-11-29 18:28 ` [PATCH 10/10] t7800: work around the MSYS path conversion on Windows Johannes Schindelin via GitGitGadget
2025-11-30 6:49 ` Junio C Hamano
2025-11-30 6:57 ` Eric Sunshine
2025-12-01 13:30 ` Johannes Schindelin
2025-12-05 15:02 ` [PATCH v2 00/10] Prepare Git's test suite for symbolic link support " Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 01/10] t9700: accommodate for Windows paths Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 02/10] apply: symbolic links lack a "trustable executable bit" Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 03/10] mingw: special-case `open(symlink, O_CREAT | O_EXCL)` Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 04/10] t0001: handle `diff --no-index` gracefully Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 05/10] t0301: another fix for Windows compatibility Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 06/10] t0600: fix incomplete prerequisite for a test case Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 07/10] t1006: accommodate for symlink support in MSYS2 Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 08/10] t1305: skip symlink tests that do not apply to Windows Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 09/10] t6423: introduce Windows-specific handling for symlinking to /dev/null Johannes Schindelin via GitGitGadget
2025-12-05 15:02 ` [PATCH v2 10/10] t7800: work around the MSYS path conversion on Windows Johannes Schindelin via GitGitGadget
2025-12-09 8:04 ` [PATCH v2 00/10] Prepare Git's test suite for symbolic link support " Patrick Steinhardt
2025-12-09 22:18 ` Junio C Hamano
2025-12-16 11:46 ` [PATCH v3 " Johannes Schindelin via GitGitGadget
2025-12-16 11:46 ` [PATCH v3 01/10] t9700: accommodate for Windows paths Johannes Schindelin via GitGitGadget
2025-12-16 11:46 ` [PATCH v3 02/10] apply: symbolic links lack a "trustable executable bit" Johannes Schindelin via GitGitGadget
2025-12-16 11:46 ` [PATCH v3 03/10] mingw: special-case `open(symlink, O_CREAT | O_EXCL)` Johannes Schindelin via GitGitGadget
2025-12-16 11:46 ` [PATCH v3 04/10] t0001: handle `diff --no-index` gracefully Johannes Schindelin via GitGitGadget
2025-12-16 11:46 ` [PATCH v3 05/10] t0301: another fix for Windows compatibility Johannes Schindelin via GitGitGadget
2025-12-16 11:46 ` [PATCH v3 07/10] t1006: accommodate for symlink support in MSYS2 Johannes Schindelin via GitGitGadget
2025-12-16 11:46 ` [PATCH v3 08/10] t1305: skip symlink tests that do not apply to Windows Johannes Schindelin via GitGitGadget
2025-12-16 11:46 ` [PATCH v3 09/10] t6423: introduce Windows-specific handling for symlinking to /dev/null Johannes Schindelin via GitGitGadget
2025-12-16 11:46 ` [PATCH v3 10/10] t7800: work around the MSYS path conversion on Windows Johannes Schindelin via GitGitGadget
2025-12-16 18:42 ` [PATCH v3 00/10] Prepare Git's test suite for symbolic link support " Junio C Hamano
2025-12-16 19:35 ` Johannes Schindelin
2025-12-17 4:31 ` Junio C Hamano
2025-12-17 14:18 ` [PATCH v4 " Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 01/10] t9700: accommodate for Windows paths Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 02/10] apply: symbolic links lack a "trustable executable bit" Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 03/10] mingw: special-case `open(symlink, O_CREAT | O_EXCL)` Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 04/10] t0001: handle `diff --no-index` gracefully Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 05/10] t0301: another fix for Windows compatibility Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 06/10] t0600: fix incomplete prerequisite for a test case Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 07/10] t1006: accommodate for symlink support in MSYS2 Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 08/10] t1305: skip symlink tests that do not apply to Windows Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 09/10] t6423: introduce Windows-specific handling for symlinking to /dev/null Johannes Schindelin via GitGitGadget
2025-12-17 14:18 ` [PATCH v4 10/10] t7800: work around the MSYS path conversion on Windows Johannes Schindelin via GitGitGadget
2025-12-17 23:19 ` [PATCH v4 00/10] Prepare Git's test suite for symbolic link support " Junio C Hamano
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