https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67193
Bug ID: 67193
Summary: Overzealous -Wstack-usage warning
Product: gcc
Version: 6.0
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: tobi at gcc dot gnu.org
Target Milestone: ---
-Wstack-usage throws a warning if it cannot prove that the stack is bounded.
Therefore it is more noisy with optimization turned off. That is fine, but
sometimes it's really too noisy, such as in this example (this is with current
trunk):
$ cat t.cc
#include <alloca.h>
void f(char *p) {
char *q = (char*)alloca(1);
*q = *p;
return;
}
$ bin/g++ -c -Wstack-usage=898989 t.cc
t.cc: In function ‘void f(char*)’:
t.cc:3:6: warning: stack usage might be unbounded [-Wstack-usage=]
void f(char *p) {
^
$ bin/g++ -O -c -Wstack-usage=898989 t.cc
$ bin/g++ --version
g++ (GCC) 6.0.0 20150812 (experimental)
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$
Constant folding should suffice to get rid of this warning but apparently
alloca is converted to some more complicated operation before the warning is
issued. (I know that alloca with a fixed argument is fairly pointless, but
this can happen with templates.)
