https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100425
Bug ID: 100425
Summary: missing -Walloca-larger-than with -O0
Product: gcc
Version: 11.1.0
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: ---
The gimple-ssa-warn-alloca.c pass only both with and without optimization and
-Walloca triggers when it's enabled but the more useful -Walloca-larger-than
fails to diagnose the excessive constant allocations because at -O0 the pass
only runs when -Walloca is enabled and not when -Walloca-larger-than. The pass
should run for both warning options even at -O0 and only diagnose the subset it
can reliably detect.
$ cat z.c && gcc -S -Wall -fdump-tree-lower=/dev/stdout
-Walloca-larger-than=100 z.c
void f (void*);
void g (void)
{
f (__builtin_alloca (1234));
}
#pragma GCC diagnostic error "-Walloca"
void h (void)
{
f (__builtin_alloca (1234));
}
;; Function g (g, funcdef_no=0, decl_uid=1945, cgraph_uid=1, symbol_order=0)
void g ()
{
_1 = __builtin_alloca (1234);
f (_1);
return;
}
;; Function h (h, funcdef_no=1, decl_uid=1948, cgraph_uid=2, symbol_order=1)
void h ()
{
_1 = __builtin_alloca (1234);
f (_1);
return;
}
z.c: In function ‘h’:
z.c:12:3: error: use of ‘alloca’ [-Werror=alloca]
12 | f (__builtin_alloca (1234));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors
