[PATCH] libio: Add __nonnull for FILE * arguments of fclose and freopen

[Xi Ruoyao <xry111@xry111.site>]

Calling fclose or freopen with a null FILE * is undefined behavior, and
doing so in practice will cause a SIGSEGV.  So it seems suitable for
__nonnull.

This will help the compiler to warn for some buggy code, like
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109570.
---
 libio/stdio.h | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/libio/stdio.h b/libio/stdio.h
index 45ddafdf20..bfb8415d3b 100644
--- a/libio/stdio.h
+++ b/libio/stdio.h
@@ -180,7 +180,7 @@ extern int renameat2 (int __oldfd, const char *__old, int __newfd,
 
    This function is a possible cancellation point and therefore not
    marked with __THROW.  */
-extern int fclose (FILE *__stream);
+extern int fclose (FILE *__stream) __nonnull ((1));
 
 #undef __attr_dealloc_fclose
 #define __attr_dealloc_fclose __attr_dealloc (fclose, 1)
@@ -269,7 +269,7 @@ extern FILE *fopen (const char *__restrict __filename,
    marked with __THROW.  */
 extern FILE *freopen (const char *__restrict __filename,
 		      const char *__restrict __modes,
-		      FILE *__restrict __stream) __wur;
+		      FILE *__restrict __stream) __wur __nonnull ((3));
 #else
 # ifdef __REDIRECT
 extern FILE *__REDIRECT (fopen, (const char *__restrict __filename,
@@ -290,7 +290,7 @@ extern FILE *fopen64 (const char *__restrict __filename,
   __attribute_malloc__ __attr_dealloc_fclose __wur;
 extern FILE *freopen64 (const char *__restrict __filename,
 			const char *__restrict __modes,
-			FILE *__restrict __stream) __wur;
+			FILE *__restrict __stream) __wur __nonnull ((3));
 #endif
 
 #ifdef	__USE_POSIX
-- 
2.40.0