On Tue, Sep 09, 2025 at 12:12:11AM +0200, Martin Uecker wrote:
> I meant a string that is valid (and also human readable)
> C representation of the type, not a mangled version.
Oh! Yes, that would be very nice too. :)
> If I am not mistaken, it would currently not agree between C and C.
>
> typedef int arr_t[];
> typedef int arr3_t[3];
>
> void f(arr3_t);
>
> void g(void (*fp)(arr_t)) {
>
> int a[3];
> (*fp)(&a); // this call would fail?
> }
>
> int h()
> {
> g(&f);
> }
Both decay to int *; the mangling ABI sees "void(int*)" as _ZTSFvPiE. I
test for this in a few ways in the last patch with adds the dg tests:
+extern void func_int_array(int arr[]); /* _ZTSFvPiE -> 0xb2a15cf9
(same as int*) */
+extern void func_int_ptr(int *x); /* _ZTSFvPiE -> 0xb2a15cf9 */
...
+extern void func_vla_1d(int n, int arr[n]); /* _ZTSFviPiE ->
0x0d1f87aa */
+extern void func_vla_empty(int n, int arr[]); /* _ZTSFviPiE ->
0x0d1f87aa */
+extern void func_vla_ptr(int n, int *arr); /* _ZTSFviPiE ->
0x0d1f87aa */
...
+extern void func_vla_2d_first(int n, int arr[n][10]); /* _ZTSFviPA10_iE
-> 0x2cd9653d */
+extern void func_vla_2d_empty(int n, int arr[][10]); /* _ZTSFviPA10_iE
-> 0x2cd9653d */
+extern void func_vla_2d_ptr(int n, int (*arr)[10]); /* _ZTSFviPA10_iE
-> 0x2cd9653d */
I can add a non-VLA numeric case, if you want, but I think it's
redundant to the others.
-Kees
--
Kees Cook
