Paul Eggert wrote:
> +#if (defined __STDC_VERSION__ && 199901L <= __STDC_VERSION__ \
> + && !defined __STDC_NO_VLA__)
> +# define __ARG_NELTS(n) n
> +#else
> +# define __ARG_NELTS(n)
> +#endif
I would suggest to add a condition __GNUC__ >= 11 in the #if.
Rationale: GCC version 10 provides reasonable diagnostics with
the __access__ attribute, but not with the VLA.
====================== foo.c ======================
int foo1 (int n, int a[])
__attribute__ ((__access__ (read_only, 2, 1)));
int foo1 (int n, int a[])
{
return a[0] + a[n-1];
}
int foo2 (int n, int a[static n]);
int foo2 (int n, int a[static n])
{
return a[0] + a[n-1];
}
void bar (int x)
{
int arr[4] = { 1, 2, 3, 4 };
foo1 (4, arr);
foo1 (5, arr);
foo2 (4, arr);
foo2 (5, arr);
}
===================================================
$ gcc-version 10.3.0 -Wall -S foo.c
foo.c: In function 'bar':
foo.c:21:3: warning: 'foo1' reading 20 bytes from a region of size 16
[-Wstringop-overflow=]
21 | foo1 (5, arr);
| ^~~~~~~~~~~~~
foo.c:5:5: note: in a call to function 'foo1' declared with attribute
'read_only (2, 1)'
5 | int foo1 (int n, int a[])
| ^~~~
$ gcc-version 11.2.0 -Wall -S foo.c
foo.c: In function 'bar':
foo.c:21:3: warning: 'foo1' reading 20 bytes from a region of size 16
[-Wstringop-overread]
21 | foo1 (5, arr);
| ^~~~~~~~~~~~~
foo.c:19:7: note: source object 'arr' of size 16
19 | int arr[4] = { 1, 2, 3, 4 };
| ^~~
foo.c:5:5: note: in a call to function 'foo1' declared with attribute 'access
(read_only, 2, 1)'
5 | int foo1 (int n, int a[])
| ^~~~
foo.c:23:3: warning: 'foo2' accessing 20 bytes in a region of size 16
[-Wstringop-overflow=]
23 | foo2 (5, arr);
| ^~~~~~~~~~~~~
foo.c:23:3: note: referencing argument 2 of type 'int *'
foo.c:12:5: note: in a call to function 'foo2'
12 | int foo2 (int n, int a[static n])
| ^~~~
Bruno
