[PATCH] Cygwin: fstatat: call fstat64 instead of fstat

[Ken Brown <kbrown@cornell.edu>]

This fixes a bug on 32-bit Cygwin that was introduced in commit
84252946, "Cygwin: fstatat, fchownat: support the AT_EMPTY_PATH flag".

Add a comment explaining why fstat should not be called.

Addresses: https://cygwin.com/pipermail/cygwin/2021-January/247399.html
---
 winsup/cygwin/release/3.2.0 | 3 +++
 winsup/cygwin/syscalls.cc   | 5 ++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/winsup/cygwin/release/3.2.0 b/winsup/cygwin/release/3.2.0
index 22f78e7a7..132d5c810 100644
--- a/winsup/cygwin/release/3.2.0
+++ b/winsup/cygwin/release/3.2.0
@@ -42,3 +42,6 @@ Bug Fixes
 
 - Fix return value of sqrtl on negative infinity.
   Addresses: https://cygwin.com/pipermail/cygwin/2020-October/246606.html
+
+- Fix a bug in fstatat(2) on 32 bit that could cause it to return garbage.
+  Addresses: https://cygwin.com/pipermail/cygwin/2021-January/247399.html
diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
index 885ca375a..525efecf3 100644
--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -1929,6 +1929,9 @@ _fstat64_r (struct _reent *ptr, int fd, struct stat *buf)
 }
 
 #ifdef __i386__
+/* This entry point is retained only to serve old 32 bit applications
+built under Cygwin 1.3.x or earlier.  Newer 32 bit apps are redirected
+to fstat64; see NEW_FUNCTIONS in Makefile.in. */
 extern "C" int
 fstat (int fd, struct stat *buf)
 {
@@ -4852,7 +4855,7 @@ fstatat (int dirfd, const char *__restrict pathname, struct stat *__restrict st,
 	      cwdstuff::cwd_lock.release ();
 	    }
 	  else
-	    return fstat (dirfd, st);
+	    return fstat64 (dirfd, st);
 	}
       path_conv pc (path, ((flags & AT_SYMLINK_NOFOLLOW)
 			   ? PC_SYM_NOFOLLOW : PC_SYM_FOLLOW)
-- 
2.30.0