Annotate additional APIs with GCC attribute access.

This change continues the improvements to compile-time out of bounds
checking by decorating more APIs with either attribute access, or by
explicitly providing the array bound in APIs such as tmpnam() that
expect arrays of some minimum size as arguments.  (The latter feature
is new in GCC 11.)

The only effects of the attribute and/or the array bound is to check
and diagnose calls to the functions that fail to provide a sufficient
number of elements, and the definitions of the functions that access
elements outside the specified bounds.  (There is no interplay with
_FORTIFY_SOURCE here yet.)

Tested with GCC 7 through 11 on x86_64-linux.

1 files changed, 5 insertions, 2 deletions

diff --git a/nss/makedb.c b/nss/makedb.c
index 74edb74..9389f6b 100644
--- a/nss/makedb.c
+++ b/nss/makedb.c
@@ -747,7 +747,8 @@ write_output (int fd)
   header->valstrlen = valstrlen;
 
   size_t filled_dbs = 0;
-  struct iovec iov[2 + ndatabases * 3];
+  size_t iov_nelts = 2 + ndatabases * 3;
+  struct iovec iov[iov_nelts];
   iov[0].iov_base = header;
   iov[0].iov_len = file_offset;
 
@@ -791,7 +792,9 @@ write_output (int fd)
 			  + nhashentries_total * sizeof (stridx_t)));
   header->allocate = file_offset;
 
-  if (writev (fd, iov, 2 + ndatabases * 3) != keydataoffset)
+  /* Help GCC 10 see iov_nelts doesn't overflow the writev argument.  */
+  assert (iov_nelts <= INT_MAX);
+  if (writev (fd, iov, iov_nelts) != keydataoffset)
     {
       error (0, errno, gettext ("failed to write new database file"));
       return EXIT_FAILURE;