Re: [PATCH] dwarf2out: Don't move variable sized aggregates to comdat [PR114015]

[Jason Merrill <jason@redhat.com>]

On 2/29/24 07:10, Jakub Jelinek wrote:
> Hi!
> 
> The following testcase ICEs, because we decide to move that
> struct { char a[n]; } DW_TAG_structure_type into .debug_types section
> / DW_UT_type DWARF5 unit, but refer from there to a DW_TAG_variable
> (created artificially for the array bounds).
> Even with non-bitint, I think it is just wrong to use .debug_types
> section / DW_UT_type for something that uses DW_OP_fbreg and similar
> in it, things clearly dependent on a particular function.
> In most cases, is_nested_in_subprogram (die) check results in such
> aggregates not being moved, but in the function parameter type case
> that is not the case.
> 
> The following patch fixes it by returning false from should_move_die_to_comdat
> for non-constant sized aggregate types, i.e. when either we gave up on
> adding DW_AT_byte_size for it because it wasn't expressable, or when
> it is something non-constant (location description, reference, ...).
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

> 2024-02-29  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR debug/114015
> 	* dwarf2out.cc (should_move_die_to_comdat): Return false for
> 	aggregates without DW_AT_byte_size attribute or with non-constant
> 	DW_AT_byte_size.
> 
> 	* gcc.dg/debug/dwarf2/pr114015.c: New test.
> 
> --- gcc/dwarf2out.cc.jj	2024-02-17 01:14:48.157790666 +0100
> +++ gcc/dwarf2out.cc	2024-02-28 17:11:44.259252850 +0100
> @@ -8215,6 +8215,15 @@ should_move_die_to_comdat (dw_die_ref di
>             || is_nested_in_subprogram (die)
>             || contains_subprogram_definition (die))
>   	return false;
> +      if (die->die_tag != DW_TAG_enumeration_type)
> +	{
> +	  /* Don't move non-constant size aggregates.  */
> +	  dw_attr_node *sz = get_AT (die, DW_AT_byte_size);
> +	  if (sz == NULL
> +	      || (AT_class (sz) != dw_val_class_unsigned_const
> +		  && AT_class (sz) != dw_val_class_unsigned_const_implicit))
> +	    return false;
> +	}
>         return true;
>       case DW_TAG_array_type:
>       case DW_TAG_interface_type:
> --- gcc/testsuite/gcc.dg/debug/dwarf2/pr114015.c.jj	2024-02-28 17:22:33.206221495 +0100
> +++ gcc/testsuite/gcc.dg/debug/dwarf2/pr114015.c	2024-02-28 17:21:49.357831730 +0100
> @@ -0,0 +1,14 @@
> +/* PR debug/114015 */
> +/* { dg-do compile { target bitint } } */
> +/* { dg-options "-g -fvar-tracking-assignments -fdebug-types-section -w" } */
> +
> +#if __BITINT_MAXWIDTH__ >= 236
> +typedef _BitInt(236) B;
> +#else
> +typedef _BitInt(63) B;
> +#endif
> +
> +int
> +foo (B n, struct { char a[n]; } o)
> +{
> +}
> 
> 	Jakub
>