[PATCH 04/18] mingw: let `mingw_lstat()` error early upon problems with reparse points

From: Karsten Blees via GitGitGadget <gitgitgadget@gmail.com>
Date: Dec 17, 2025, 14:08 UTC
Message-ID: <886044373be1bd4d2e7ecf758c42474e9efbe067.1765980535.git.gitgitgadget@gmail.com>
In-Reply-To: <pull.2018.git.1765980535.gitgitgadget@gmail.com>

From: Karsten Blees <blees@dcon.de>

When obtaining lstat information for reparse points, we need to call `FindFirstFile()` in addition to `GetFileInformationEx()` to obtain the type of the reparse point (symlink, mount point etc.). However, currently there is no error handling whatsoever if `FindFirstFile()` fails.

Call `FindFirstFile()` before modifying the `stat *buf` output parameter and error out if the call fails.

Note: The `FindFirstFile()` return value includes all the data
that we get from `GetFileAttributesEx()`, so we could replace
`GetFileAttributesEx()` with `FindFirstFile()`. We don't do that because
`GetFileAttributesEx()` is about twice as fast for single files. I.e.
we only pay the extra cost of calling `FindFirstFile()` in the rare case
that we encounter a reparse point.

Please also note that the indentation the remaining reparse point code changed, and hence the best way to look at this diff is with `--color-moved -w`. That code was _not_ moved because a subsequent commit will move it to an altogether different function, anyway.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 compat/mingw.c | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/compat/mingw.c b/compat/mingw.c
index ec6c2801d3..23a926c7d1 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -920,6 +920,7 @@ static int has_valid_directory_prefix(wchar_t *wfilename)
 int mingw_lstat(const char *file_name, struct stat *buf)
 {
 	WIN32_FILE_ATTRIBUTE_DATA fdata;
+	WIN32_FIND_DATAW findbuf = { 0 };
 	wchar_t wfilename[MAX_PATH];
 	int wlen = xutftowcs_path(wfilename, file_name);
 	if (wlen < 0)
@@ -934,6 +935,13 @@ int mingw_lstat(const char *file_name, struct stat *buf)
 	}
 
 	if (GetFileAttributesExW(wfilename, GetFileExInfoStandard, &fdata)) {
+		/* for reparse points, use FindFirstFile to get the reparse tag */
+		if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
+			HANDLE handle = FindFirstFileW(wfilename, &findbuf);
+			if (handle == INVALID_HANDLE_VALUE)
+				goto error;
+			FindClose(handle);
+		}
 		buf->st_ino = 0;
 		buf->st_gid = 0;
 		buf->st_uid = 0;
@@ -946,20 +954,16 @@ int mingw_lstat(const char *file_name, struct stat *buf)
 		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)) {
-					buf->st_mode = S_IFLNK | S_IREAD;
-					if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY))
-						buf->st_mode |= S_IWRITE;
-				}
-				FindClose(handle);
+			if ((findbuf.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) &&
+					(findbuf.dwReserved0 == IO_REPARSE_TAG_SYMLINK)) {
+				buf->st_mode = S_IFLNK | S_IREAD;
+				if (!(findbuf.dwFileAttributes & FILE_ATTRIBUTE_READONLY))
+					buf->st_mode |= S_IWRITE;
 			}
 		}
 		return 0;
 	}
+error:
 	switch (GetLastError()) {
 	case ERROR_ACCESS_DENIED:
 	case ERROR_SHARING_VIOLATION:

-- 
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