[PATCH] Fix GCC 8's -Wstringop-overflow on bfd/coff-rs6000.c

[Sergio Durigan Junior]

GCC 8 will bring a new warning option which will detect possible
overflow and truncation on string manipulation functions.  For more
details, see:

  https://gcc.gnu.org/ml/gcc-patches/2017-08/msg00471.html

While compiling BFD with it, I can see one place on bfd/coff-rs6000.c
where the warning is triggered.  This:

  (void) strncpy (fhdr.magic, XCOFFARMAG, SXCOFFARMAG);

will not include the trailing NUL on fhdr.magic, but that's fine
because it's a magic number.  The fix is trivial: just use memcpy
instead.

OK to push?

2018-02-05  Sergio Durigan Junior  <sergiodj@redhat.com>

	* coff-rs6000.c (xcoff_write_archive_contents_old): Use
	'memcpy' instead of 'strncpy' when writing the magic number.
---
 bfd/coff-rs6000.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/bfd/coff-rs6000.c b/bfd/coff-rs6000.c
index 2fc1feb1c5..d02835ede6 100644
--- a/bfd/coff-rs6000.c
+++ b/bfd/coff-rs6000.c
@@ -2090,7 +2090,7 @@ xcoff_write_archive_contents_old (bfd *abfd)
   char decbuf[XCOFFARMAG_ELEMENT_SIZE + 1];
 
   memset (&fhdr, 0, sizeof fhdr);
-  (void) strncpy (fhdr.magic, XCOFFARMAG, SXCOFFARMAG);
+  (void) memcpy (fhdr.magic, XCOFFARMAG, SXCOFFARMAG);
   sprintf (fhdr.firstmemoff, "%d", SIZEOF_AR_FILE_HDR);
   sprintf (fhdr.freeoff, "%d", 0);
 
-- 
2.14.3