Use __builtin___stpncpy_chk when available

The builtin has been available in gcc since 4.7.0 and in clang since
2.6.  This fixes stpncpy fortification with clang since it does a
better job of plugging in __stpncpy_chk in the right place than the
header hackery.

This has been tested by building and running all tests with gcc 10.2.1
and also with clang tip as of a few days ago (just the tests in debug/
since running all tests don't work with clang at the moment) to make
sure that both compilers pass the stpncpy tests.

1 files changed, 8 insertions, 1 deletions

diff --git a/string/bits/string_fortified.h b/string/bits/string_fortified.h
index c8d3051af8..4c1aeb45f1 100644
--- a/string/bits/string_fortified.h
+++ b/string/bits/string_fortified.h
@@ -91,7 +91,13 @@ __NTH (strncpy (char *__restrict __dest, const char *__restrict __src,
   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
 }
 
-/* XXX We have no corresponding builtin yet.  */
+#if __GNUC_PREREQ (4, 7) || __glibc_clang_prereq (2, 6)
+__fortify_function char *
+__NTH (stpncpy (char *__dest, const char *__src, size_t __n))
+{
+  return __builtin___stpncpy_chk (__dest, __src, __n, __bos (__dest));
+}
+#else
 extern char *__stpncpy_chk (char *__dest, const char *__src, size_t __n,
 			    size_t __destlen) __THROW
   __attr_access ((__write_only__, 1, 3)) __attr_access ((__read_only__, 2));
@@ -106,6 +112,7 @@ __NTH (stpncpy (char *__dest, const char *__src, size_t __n))
     return __stpncpy_chk (__dest, __src, __n, __bos (__dest));
   return __stpncpy_alias (__dest, __src, __n);
 }
+#endif
 
 
 __fortify_function char *