From 980852dbff657a14eecc4a8a72a2874dad2bad71 Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Fri, 9 Jan 2026 20:05:10 +0000 Subject: [PATCH] mingw: implement `readlink()` Implement `readlink()` by reading NTFS reparse points via the `read_reparse_point()` function that was introduced earlier to determine the length of symlink targets. Works for symlinks and directory junctions. Signed-off-by: Karsten Blees Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- compat/mingw-posix.h | 3 +-- compat/mingw.c | 24 ++++++++++++++++++++++++ 2 files changed, 25 insertions(+), 2 deletions(-) diff --git a/compat/mingw-posix.h b/compat/mingw-posix.h index 0939feff27..896aa976b1 100644 --- a/compat/mingw-posix.h +++ b/compat/mingw-posix.h @@ -121,8 +121,6 @@ struct utsname { * trivial stubs */ -static inline int readlink(const char *path UNUSED, char *buf UNUSED, size_t bufsiz UNUSED) -{ errno = ENOSYS; return -1; } static inline int symlink(const char *oldpath UNUSED, const char *newpath UNUSED) { errno = ENOSYS; return -1; } static inline int fchmod(int fildes UNUSED, mode_t mode UNUSED) @@ -197,6 +195,7 @@ int setitimer(int type, struct itimerval *in, struct itimerval *out); int sigaction(int sig, struct sigaction *in, struct sigaction *out); int link(const char *oldpath, const char *newpath); int uname(struct utsname *buf); +int readlink(const char *path, char *buf, size_t bufsiz); /* * replacements of existing functions diff --git a/compat/mingw.c b/compat/mingw.c index 5d2a8c247c..b407a2ac07 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -2698,6 +2698,30 @@ int link(const char *oldpath, const char *newpath) return 0; } +int readlink(const char *path, char *buf, size_t bufsiz) +{ + WCHAR wpath[MAX_PATH]; + char tmpbuf[MAX_PATH]; + int len; + DWORD tag; + + if (xutftowcs_path(wpath, path) < 0) + return -1; + + if (read_reparse_point(wpath, TRUE, tmpbuf, &len, &tag) < 0) + return -1; + + /* + * Adapt to strange readlink() API: Copy up to bufsiz *bytes*, potentially + * cutting off a UTF-8 sequence. Insufficient bufsize is *not* a failure + * condition. There is no conversion function that produces invalid UTF-8, + * so convert to a (hopefully large enough) temporary buffer, then memcpy + * the requested number of bytes (including '\0' for robustness). + */ + memcpy(buf, tmpbuf, min(bufsiz, len + 1)); + return min(bufsiz, len); +} + pid_t waitpid(pid_t pid, int *status, int options) { HANDLE h = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_INFORMATION,