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author | Eric Blake <eblake@redhat.com> | 2023-01-13 16:27:54 -0600 |
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committer | Eric Blake <eblake@redhat.com> | 2023-01-13 16:33:49 -0600 |
commit | a886ea40a29a08954ff80772e267828a1d440cc9 (patch) | |
tree | 12735a422564469ae816fef43b15275919c0d392 | |
parent | dd434e3e958b3cebde954d66010919a40665812e (diff) | |
download | m4-a886ea40a29a08954ff80772e267828a1d440cc9.tar.gz |
output: Avoid tickling UBSAN with memcpy(dest, NULL, 0)branch-1.4
Even though all libc handle it sanely (because size 0 says there is
nothing to copy), NULL is not a valid source pointer per a strict
reading of C, so UBSAN flags it:
+output.c:511:9: runtime error: null pointer passed as argument 2, which is declared to never be null
* src/output.c (make_room_for): Skip no-op memcpy.
Fixes: https://savannah.gnu.org/support/index.php?110809
Reported-by: Sam James
-rw-r--r-- | src/output.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/src/output.c b/src/output.c index 956089b1..6dc8280a 100644 --- a/src/output.c +++ b/src/output.c @@ -508,7 +508,8 @@ make_room_for (int length) { char *buffer = output_diversion->u.buffer; output_diversion->u.buffer = xcharalloc ((size_t) wanted_size); - memcpy (output_diversion->u.buffer, buffer, output_diversion->used); + if (output_diversion->used) + memcpy (output_diversion->u.buffer, buffer, output_diversion->used); free (buffer); } |