https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110830
Bug ID: 110830
Summary: -Wanalyzer-use-of-uninitialized-value false negative
due to use-after-free::supercedes_p.
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: analyzer
Assignee: dmalcolm at gcc dot gnu.org
Reporter: vultkayn at gcc dot gnu.org
Target Milestone: ---
state_machine::supercedes_p is called when two diagnostics are emitted for the
same statement, without regarding the path that led to this statement.
See reproducer on trunk https://godbolt.org/z/GqebW5s5h
#include <stdlib.h>
extern int ext();
int* foo()
{
int *p = 0;
if (ext() > 5)
{
p = malloc (sizeof(int));
*p = 0;
free (p);
return p;
}
else
return malloc(sizeof(int));
}
void test()
{
int *y = foo(); // (*)
int x = 4 + *y;
free (y);
}
At statement (*) both -Wanalyzer-use-of-uninitialized-value and
-Wanalyzer-use-after-free should be emitted as solving the latter won't impact
the former, since they result from two independent branches. But
use_after_free::supercedes_p hides the other.
In the case of a false positive -Wanalyzer-use-after-free, or simply one
ignored by the user, the adjacent -Wanalyzer-use-of-uninitialized-value would
therefore never be emitted.
