Re: [PATCH 1/2] Fix ICE due to c_safe_arg_type_equiv_p not checking for error_mark node

[Marek Polacek <polacek@redhat.com>]

On Sat, Oct 14, 2023 at 06:16:47PM -0700, Andrew Pinski wrote:
> This is a simple error recovery issue when c_safe_arg_type_equiv_p
> was added in r8-5312-gc65e18d3331aa999. The issue is that after
> an error, an argument type (of a function type) might turn
> into an error mark node and c_safe_arg_type_equiv_p was not ready
> for that. So this just adds a check for error operand for its
> arguments before getting the main variant.
> 
> OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

Please don't include this line in the commit message.
 
> 	PR c/101285
> 
> gcc/c/ChangeLog:
> 
> 	* c-typeck.cc (c_safe_arg_type_equiv_p): Return true for error
> 	operands early.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* gcc.dg/pr101285-1.c: New test.
> ---
>  gcc/c/c-typeck.cc                 |  3 +++
>  gcc/testsuite/gcc.dg/pr101285-1.c | 10 ++++++++++
>  2 files changed, 13 insertions(+)
>  create mode 100644 gcc/testsuite/gcc.dg/pr101285-1.c
> 
> diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
> index e55e887da14..6e044b4afbc 100644
> --- a/gcc/c/c-typeck.cc
> +++ b/gcc/c/c-typeck.cc
> @@ -5960,6 +5960,9 @@ handle_warn_cast_qual (location_t loc, tree type, tree otype)
>  static bool
>  c_safe_arg_type_equiv_p (tree t1, tree t2)
>  {
> +  if (error_operand_p (t1) || error_operand_p (t2))
> +    return true;

I thought it would be more natural to return false but that would result in:
cast between incompatible function types from 'void (*)(int *)' to 'void (*)(<type-error>)'
but we don't want that so pretending the cast is safe is probably better.

>    t1 = TYPE_MAIN_VARIANT (t1);
>    t2 = TYPE_MAIN_VARIANT (t2);
>  
> diff --git a/gcc/testsuite/gcc.dg/pr101285-1.c b/gcc/testsuite/gcc.dg/pr101285-1.c
> new file mode 100644
> index 00000000000..831e35f7662
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101285-1.c
> @@ -0,0 +1,10 @@

Let's put

/* PR c/101285 */

here.

> +/* { dg-do compile } */
> +/* { dg-options "-W -Wall" } */
> +const int b;
> +typedef void (*ft1)(int[b++]); /* { dg-error "read-only variable" } */
> +void bar(int * z);
> +void baz()
> +{
> +    (ft1) bar; /* { dg-warning "statement with no effect" } */
> +}
> +

Extra newline.

Thanks,
Marek