https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109395
Bug ID: 109395
Summary: -Wvla-larger-than has no effect when compiling without
optimizations
Product: gcc
Version: 12.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: dev at joren dot ga
Target Milestone: ---
Let's take the following for an example:
int bar(int n, int[n]);
void foo(int n)
{
int arr[n];
for (int i = 0; i < n; ++i) {
arr[i] = i;
}
bar(n, arr);
}
When compiled with
$ gcc -O -Wvla-larger-than=0 -c foo.c
a warning is shown as expected:
foo.c: In function ‘foo’:
foo.c:5:9: warning: argument to variable-length array may be too large
[-Wvla-larger-than=]
5 | int arr[n];
| ^~~
It works with -O, -O1, -O2, -O3, -Os, -Oz, -Ofast
On the other hand, when compiling with -O0, -Og or no -O flag, no warning is
triggered (https://godbolt.org/z/Penjbqojh).
I've tried to find if only a flag implied by optimization is required, but to
no avail.
