https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90264
Bug ID: 90264
Summary: [9/10 Regression] -Wnull-dereference false positive
after r270574
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zhroma at gcc dot gnu.org
CC: jakub at gcc dot gnu.org, law at redhat dot com, rguenth at
gcc dot gnu.org
Blocks: 86172
Target Milestone: ---
Reduced manually from lib/colors.c in util-linux 2.33.1
int like_asprintf(char **strp);
int cn_sequence(char **seq) {
char *out;
int len;
*seq = 0;
/* Warning disappears when using second line
(comment line A and uncomment line B). */
if ((len = like_asprintf(seq)) < 1) return -1; //line A
//len = like_asprintf(seq); //line B
for (out = *seq; out && *out; out++);
if ((out - *seq) > len) return -2;
*out = '\0';
return 0;
}
with "-O2 -Wnull-dereference"
<source>: In function 'cn_sequence':
<source>:13:8: warning: potential null pointer dereference [-Wnull-dereference]
13 | *out = '\0';
| ~~~~~^~~~~~
It seems odd to have warning with "line A" version and not to warn in "line B"
example.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86172
[Bug 86172] [meta-bug] issues with -Wnull-dereference
