https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108246
Bug ID: 108246
Summary: False-positive Wanalyzer-double-fclose on fclose() in
loop
Product: gcc
Version: 11.3.1
Status: UNCONFIRMED
Keywords: diagnostic
Severity: normal
Priority: P3
Component: analyzer
Assignee: dmalcolm at gcc dot gnu.org
Reporter: roman.zilka at gmail dot com
Target Milestone: ---
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
Build: x86_64-pc-linux-gnu
Created attachment 54164
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54164&action=edit
gcc -v
Encountered a false-positive -Wanalyzer-double-fclose in -fanalyzer in gcc
11.3.1 and 12.2. It's accompanied by -Wanalyzer-double-free, but only in the
11.3.1.
$ cat false_fanalyzer.c
#include <stdio.h>
#include <errno.h>
int main() {
FILE *f = fopen("/dev/null", "w");
if (f) {
fwrite("asd", 1, 3, f);
while (fclose(f)) {
if (errno != EINTR)
break;
}
}
}
$ gcc -fanalyzer -fanalyzer-verbosity=0 false_fanalyzer.c
false_fanalyzer.c: In function ‘main’:
false_fanalyzer.c:7:16: warning: double ‘fclose’ of FILE ‘f’
[-Wanalyzer-double-fclose]
7 | while (fclose(f)) {
| ^~~~~~~~~
‘main’: events 1-4
|
| 4 | FILE *f = fopen("/dev/null", "w");
| | ^~~~~~~~~~~~~~~~~~~~~~~
| | |
| | (1) opened here
| 5 | if (f) {
| | ~
| | |
| | (2) assuming ‘f’ is non-NULL
| 6 | fwrite("asd", 1, 3, f);
| 7 | while (fclose(f)) {
| | ~~~~~~~~~
| | |
| | (3) first ‘fclose’ here
| | (4) second ‘fclose’ here; first ‘fclose’ was at (3)
|
false_fanalyzer.c:7:16: warning: double-‘fclose’ of ‘f’ [CWE-415]
[-Wanalyzer-double-free]
7 | while (fclose(f)) {
| ^~~~~~~~~
‘main’: events 1-4
|
| 4 | FILE *f = fopen("/dev/null", "w");
| | ^~~~~~~~~~~~~~~~~~~~~~~
| | |
| | (1) allocated here
| 5 | if (f) {
| | ~
| | |
| | (2) assuming ‘f’ is non-NULL
| 6 | fwrite("asd", 1, 3, f);
| 7 | while (fclose(f)) {
| | ~~~~~~~~~
| | |
| | (3) first ‘fclose’ here
| | (4) second ‘fclose’ here; first ‘fclose’ was at (3)
|
