https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103352
Bug ID: 103352
Summary: Wrong computation of -Wformat-truncation=2
Product: gcc
Version: 10.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: julien at trigofacile dot com
Target Milestone: ---
When building
https://raw.githubusercontent.com/InterNetNews/inn/main/lib/timer.c I have a
warning with -Wformat-truncation=2
len = 52 * timer_count + 27 + (prefix == NULL ? 0 : strlen(prefix)) + 1;
buf = xmalloc(len);
if (prefix == NULL)
rc = 0;
else
rc = snprintf(buf, len, "%s ", prefix);
timer.c: In function ‘TMRsummary’:
timer.c:395:36: warning: ‘ ’ directive output may be truncated writing 1 byte
into a region of size between 0 and 1 [-Wformat-truncation=]
395 | rc = snprintf(buf, len, "%s ", prefix);
| ^
timer.c:395:14: note: ‘snprintf’ output 2 or more bytes (assuming 3) into a
destination of size 1
395 | rc = snprintf(buf, len, "%s ", prefix);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It seems that "len" is considered to be of length 1. I bet it comes from the
"+ 1" at the end of the declaration of "len".
If I move the "+ 27" at the end of the declaration of "len", the warning
disappears.
Isn't there something to improve in the way the computation is done for that
warning?
Thanks beforehand.
