Re: [C PATCH, v2] Fix ICE with -g and -std=c23 related to incomplete types [PR114361]

[Richard Biener <rguenther@suse.de>]

On Sun, 14 Apr 2024, Martin Uecker wrote:

> 
> I had to revert the old patch because it broke LTO which lead
> to PR114574.  We now set TYPE_STRUCTURAL_EQUALITY and properly
> update TYPE_CANONICAL for such types and also for pointers
> to such types via a new function c_update_type_canonical
> (thanks to Jakob).
> 
> 
> Bootstrapped and regession tested on x86_64.
> 
> 
> 
> Fix ICE with -g and -std=c23 related to incomplete types [PR114361]
> 
> We did not update TYPE_CANONICAL for incomplete variants when
> completing a structure.  We now set TYPE_STRUCTURAL_EQUALITY for
> incomplete structure and union types and then update TYPE_CANONICAL
> later. See PR114574 for discussion.
> 
> 
> 2024-04-12  Martin Uecker  <uecker@tugraz.at>
> 	    Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR lto/114574
> 	PR c/114361
> gcc/
> 	* ipa-free-lang-data.cc (fld_incomplete_type_of): Allow
> 	either of the types in the assert to have TYPE_STRUCTURAL_EQUALITY_P.
> gcc/c/
> 	* c-decl.cc (shadow_tag_warned): For flag_isoc23 and code not
> 	ENUMERAL_TYPE use SET_TYPE_STRUCTURAL_EQUALITY.
> 	(parser_xref_tag): Likewise.
> 	(start_struct): For flag_isoc23 use SET_TYPE_STRUCTURAL_EQUALITY.
> 	(c_update_type_canonical): New function.
> 	(finish_struct): Put NULL as second == operand rather than first.
> 	Assert TYPE_STRUCTURAL_EQUALITY_P.  Call c_update_type_canonical.
> 	* c-typeck.cc (composite_type_internal): Use
> 	SET_TYPE_STRUCTURAL_EQUALITY.  Formatting fix.
> gcc/testsuite/
> 	* gcc.dg/pr114574-1.c: New test.
> 	* gcc.dg/pr114574-2.c: New test.
> 	* gcc.dg/pr114361.c: New test.
> 	* gcc.dg/c23-tag-incomplete-1.c: New test.
> 	* gcc.dg/c23-tag-incomplete-2.c: New test.
> ---
>  gcc/c/c-decl.cc                             | 47 ++++++++++++++++++++-
>  gcc/c/c-typeck.cc                           |  4 +-
>  gcc/ipa-free-lang-data.cc                   |  4 +-
>  gcc/testsuite/gcc.dg/c23-tag-incomplete-1.c | 14 ++++++
>  gcc/testsuite/gcc.dg/c23-tag-incomplete-2.c | 13 ++++++
>  gcc/testsuite/gcc.dg/pr114361.c             | 11 +++++
>  gcc/testsuite/gcc.dg/pr114574-1.c           | 10 +++++
>  gcc/testsuite/gcc.dg/pr114574-2.c           | 10 +++++
>  8 files changed, 110 insertions(+), 3 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.dg/c23-tag-incomplete-1.c
>  create mode 100644 gcc/testsuite/gcc.dg/c23-tag-incomplete-2.c
>  create mode 100644 gcc/testsuite/gcc.dg/pr114361.c
>  create mode 100644 gcc/testsuite/gcc.dg/pr114574-1.c
>  create mode 100644 gcc/testsuite/gcc.dg/pr114574-2.c
> 
> diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
> index 345090dae38..54917297b6a 100644
> --- a/gcc/c/c-decl.cc
> +++ b/gcc/c/c-decl.cc
> @@ -5051,6 +5051,8 @@ shadow_tag_warned (const struct c_declspecs *declspecs, int warned)
>  	      if (t == NULL_TREE)
>  		{
>  		  t = make_node (code);
> +		  if (flag_isoc23 && code != ENUMERAL_TYPE)
> +		    SET_TYPE_STRUCTURAL_EQUALITY (t);
>  		  pushtag (input_location, name, t);
>  		}
>  	    }
> @@ -8809,6 +8811,8 @@ parser_xref_tag (location_t loc, enum tree_code code, tree name,
>       the forward-reference will be altered into a real type.  */
>  
>    ref = make_node (code);
> +  if (flag_isoc23 && code != ENUMERAL_TYPE)
> +    SET_TYPE_STRUCTURAL_EQUALITY (ref);
>    if (code == ENUMERAL_TYPE)
>      {
>        /* Give the type a default layout like unsigned int
> @@ -8910,6 +8914,8 @@ start_struct (location_t loc, enum tree_code code, tree name,
>    if (ref == NULL_TREE || TREE_CODE (ref) != code)
>      {
>        ref = make_node (code);
> +      if (flag_isoc23)
> +	SET_TYPE_STRUCTURAL_EQUALITY (ref);
>        pushtag (loc, name, ref);
>      }
>  
> @@ -9347,6 +9353,43 @@ is_flexible_array_member_p (bool is_last_field,
>    return false;
>  }
>  
> +/* Recompute TYPE_CANONICAL for qualified versions of the type and
> +   related pointer types after an aggregate type has been finalized.
> +   Will not update array types, pointers to array types, function
> +   types and other derived types created while the type was still
> +   incomplete, those will remain TYPE_STRUCTURAL_EQUALITY_P.  */
> +
> +static void
> +c_update_type_canonical (tree t)
> +{
> +  for (tree x = TYPE_MAIN_VARIANT (t); x; x = TYPE_NEXT_VARIANT (x))
> +    {
> +      if (x != t
> +	  && TYPE_STRUCTURAL_EQUALITY_P (x)
> +	  && check_qualified_type (x, t, TYPE_QUALS (x)))
> +	{
> +	  if (TYPE_CANONICAL (t) != t)
> +	    TYPE_CANONICAL (x)
> +	      = build_qualified_type (TYPE_CANONICAL (t), TYPE_QUALS (x));
> +	  else
> +	    TYPE_CANONICAL (x) = x;
> +	}
> +      else if (x != t)
> +	continue;
> +      for (tree p = TYPE_POINTER_TO (x); p; p = TYPE_NEXT_PTR_TO (p))
> +	{
> +	  if (!TYPE_STRUCTURAL_EQUALITY_P (p))
> +	    continue;
> +	  if (TYPE_CANONICAL (x) != x || TYPE_REF_CAN_ALIAS_ALL (p))
> +	    TYPE_CANONICAL (p)
> +	      = build_pointer_type_for_mode (TYPE_CANONICAL (x), TYPE_MODE (p),
> +					     false);
> +	  else
> +	    TYPE_CANONICAL (p) = p;
> +	  c_update_type_canonical (p);
> +	}
> +    }
> +}
>  
>  /* Fill in the fields of a RECORD_TYPE or UNION_TYPE node, T.
>     LOC is the location of the RECORD_TYPE or UNION_TYPE's definition.
> @@ -9695,11 +9738,12 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes,
>    /* Set type canonical based on equivalence class.  */
>    if (flag_isoc23)
>      {
> -      if (NULL == c_struct_htab)
> +      if (c_struct_htab == NULL)
>  	c_struct_htab = hash_table<c_struct_hasher>::create_ggc (61);
>  
>        hashval_t hash = c_struct_hasher::hash (t);
>  
> +      gcc_checking_assert (TYPE_STRUCTURAL_EQUALITY_P (t));
>        tree *e = c_struct_htab->find_slot_with_hash (t, hash, INSERT);
>        if (*e)
>  	TYPE_CANONICAL (t) = *e;
> @@ -9708,6 +9752,7 @@ finish_struct (location_t loc, tree t, tree fieldlist, tree attributes,
>  	  TYPE_CANONICAL (t) = t;
>  	  *e = t;
>  	}
> +      c_update_type_canonical (t);
>      }
>  
>    tree incomplete_vars = C_TYPE_INCOMPLETE_VARS (TYPE_MAIN_VARIANT (t));
> diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
> index ddeab1e2a8a..4567b114734 100644
> --- a/gcc/c/c-typeck.cc
> +++ b/gcc/c/c-typeck.cc
> @@ -532,6 +532,7 @@ composite_type_internal (tree t1, tree t2, struct composite_cache* cache)
>  	  /* Otherwise, create a new type node and link it into the cache.  */
>  
>  	  tree n = make_node (code1);
> +	  SET_TYPE_STRUCTURAL_EQUALITY (n);
>  	  TYPE_NAME (n) = TYPE_NAME (t1);
>  
>  	  struct composite_cache cache2 = { t1, t2, n, cache };
> @@ -590,7 +591,8 @@ composite_type_internal (tree t1, tree t2, struct composite_cache* cache)
>  	  TYPE_STUB_DECL (n) = pushdecl (build_decl (input_location, TYPE_DECL,
>  						     NULL_TREE, n));
>  
> -	  n = finish_struct(input_location, n, fields, attributes, NULL, &expr);
> +	  n = finish_struct (input_location, n, fields, attributes, NULL,
> +			     &expr);
>  
>  	  n = qualify_type (n, t1);
>  
> diff --git a/gcc/ipa-free-lang-data.cc b/gcc/ipa-free-lang-data.cc
> index 16ed55e2e5a..6f75444e513 100644
> --- a/gcc/ipa-free-lang-data.cc
> +++ b/gcc/ipa-free-lang-data.cc
> @@ -255,7 +255,9 @@ fld_incomplete_type_of (tree t, class free_lang_data_d *fld)
>  	    first = build_reference_type_for_mode (t2, TYPE_MODE (t),
>  						   TYPE_REF_CAN_ALIAS_ALL (t));
>  	  gcc_assert (TYPE_CANONICAL (t2) != t2
> -		      && TYPE_CANONICAL (t2) == TYPE_CANONICAL (TREE_TYPE (t)));
> +		      && (TYPE_CANONICAL (t2) == TYPE_CANONICAL (TREE_TYPE (t))
> +			  || TYPE_STRUCTURAL_EQUALITY_P (t2)
> +			  || TYPE_STRUCTURAL_EQUALITY_P (TREE_TYPE (t))));

I think we want the same canonical types for t2 and TREE_TYPE (t), why
doesn't fld_incomplete_type_of make it so?

Richard.

>  	  if (!fld->pset.add (first))
>  	    add_tree_to_fld_list (first, fld);
>  	  return fld_type_variant (first, t, fld);
> diff --git a/gcc/testsuite/gcc.dg/c23-tag-incomplete-1.c b/gcc/testsuite/gcc.dg/c23-tag-incomplete-1.c
> new file mode 100644
> index 00000000000..82d652569e9
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/c23-tag-incomplete-1.c
> @@ -0,0 +1,14 @@
> +/* { dg-do compile }
> + * { dg-options "-std=c23 -g" } */
> +
> +struct a;
> +typedef struct a b;
> +
> +void g() {
> +    struct a { b* x; };
> +}
> +
> +struct a { b* x; };
> +
> +
> +
> diff --git a/gcc/testsuite/gcc.dg/c23-tag-incomplete-2.c b/gcc/testsuite/gcc.dg/c23-tag-incomplete-2.c
> new file mode 100644
> index 00000000000..bc47a04ece5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/c23-tag-incomplete-2.c
> @@ -0,0 +1,13 @@
> +/* { dg-do compile }
> + * { dg-options "-std=c23 -g" } */
> +
> +struct a;
> +typedef struct a b;
> +
> +void f() {
> +	extern struct a { b* x; } t;
> +}
> +
> +extern struct a { b* x; } t;
> +
> +
> diff --git a/gcc/testsuite/gcc.dg/pr114361.c b/gcc/testsuite/gcc.dg/pr114361.c
> new file mode 100644
> index 00000000000..0f3feb53566
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr114361.c
> @@ -0,0 +1,11 @@
> +/* PR c/114361 */
> +/* { dg-do compile } */
> +/* { dg-options "-std=gnu23 -g" } */
> +
> +void f()
> +{
> +    typedef struct foo bar;
> +    typedef __typeof( ({ (struct foo { bar *x; }){ }; }) ) wuz;
> +    struct foo { wuz *x; };
> +}
> +
> diff --git a/gcc/testsuite/gcc.dg/pr114574-1.c b/gcc/testsuite/gcc.dg/pr114574-1.c
> new file mode 100644
> index 00000000000..060dcdbe73e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr114574-1.c
> @@ -0,0 +1,10 @@
> +/* PR lto/114574
> + * { dg-do compile }
> + * { dg-options "-flto" } */
> +
> +const struct S * x;
> +struct S {};
> +void f(const struct S **);
> +
> +
> +
> diff --git a/gcc/testsuite/gcc.dg/pr114574-2.c b/gcc/testsuite/gcc.dg/pr114574-2.c
> new file mode 100644
> index 00000000000..723291e2211
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr114574-2.c
> @@ -0,0 +1,10 @@
> +/* PR lto/114574
> + * { dg-do compile }
> + * { dg-options "-flto -std=c23" } */
> +
> +const struct S * x;
> +struct S {};
> +void f(const struct S **);
> +
> +
> +
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)