https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96296
Bug ID: 96296
Summary: libiberty/dyn-string.c:280:3: warning: ‘strncpy’
output truncated before terminating nul copying as
many bytes from a string as its length
[-Wstringop-truncation]
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: vries at gcc dot gnu.org
Target Milestone: ---
[ Reported and discussed earlier here:
https://gcc.gnu.org/legacy-ml/gcc/2019-03/msg00184.html ]
I ran into this warning in dyn-string.c:
...
$ gcc-11 src/libiberty/dyn-string.c -I src/include/ -c -DHAVE_STRING_H
-DHAVE_STDLIB_H -Wall -O2
src/libiberty/dyn-string.c: In function ‘dyn_string_insert_cstr’:
src/libiberty/dyn-string.c:280:3: warning: ‘strncpy’ output truncated before
terminating nul copying as many bytes from a string as its length
[-Wstringop-truncation]
280 | strncpy (dest->s + pos, src, length);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
src/libiberty/dyn-string.c:272:16: note: length computed here
272 | int length = strlen (src);
| ^~~~~~~~~~~~
...
As mentioned here ( https://gcc.gnu.org/legacy-ml/gcc/2019-03/msg00199.html ):
"Using memcpy instead of strncpy would avoid the warning".
Tentative untested patch fixes the warning:
...
diff --git a/libiberty/dyn-string.c b/libiberty/dyn-string.c
index e10f691181a..bf155effb5f 100644
--- a/libiberty/dyn-string.c
+++ b/libiberty/dyn-string.c
@@ -277,7 +277,7 @@ dyn_string_insert_cstr (dyn_string_t dest, int pos, const
char *sr
c)
for (i = dest->length; i >= pos; --i)
dest->s[i + length] = dest->s[i];
/* Splice in the new stuff. */
- strncpy (dest->s + pos, src, length);
+ memcpy (dest->s + pos, src, length);
/* Compute the new length. */
dest->length += length;
return 1;
...
