https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98166
Bug ID: 98166
Summary: bogus -Wmismatched-dealloc on user-defined allocator
and inlining
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
Designating using attribute malloc a pair of functions as an allocator and
deallocator and defining one of them inline to call another allocator or
deallocator not associated with the former pair leads to false positive
warnings.
The test case below (inspired by the one in pr98160) shows how this could
happen. The two pairs of allocators are independent with one another
$ cat a.c && gcc -O2 -S -Wall a.c
void dealloc_shrt (short *p) { __builtin_free (p - 1); }
void dealloc_int (int*);
__attribute__ ((malloc (dealloc_shrt)))
short* alloc_shrt (int);
__attribute__ ((malloc (dealloc_int)))
int* alloc_int (int n) { return (int*)__builtin_malloc (n) + 1; }
void f (int n)
{
{
short *p = alloc_shrt (n);
dealloc_shrt (p);
}
{
int *p = alloc_int (n);
dealloc_int (p);
}
}
In function ‘dealloc_shrt’,
inlined from ‘f’ at a.c:14:5:
a.c:1:32: warning: ‘__builtin_free’ called on pointer returned from a
mismatched allocation function [-Wmismatched-dealloc]
1 | void dealloc_shrt (short *p) { __builtin_free (p - 1); }
| ^~~~~~~~~~~~~~~~~~~~~~
a.c: In function ‘f’:
a.c:13:16: note: returned from a call to ‘alloc_shrt’
13 | short *p = alloc_shrt (n);
| ^~~~~~~~~~~~~~
a.c:19:5: warning: ‘dealloc_int’ called on pointer returned from a mismatched
allocation function [-Wmismatched-dealloc]
19 | dealloc_int (p);
| ^~~~~~~~~~~~~~~
a.c:8:39: note: returned from a call to ‘__builtin_malloc’
8 | int* alloc_int (int n) { return (int*)__builtin_malloc (n) + 1; }
| ^~~~~~~~~~~~~~~~~~~~
