hash-table violation in gcc/cp/pt.c

[Martin Liška]

On 10/29/18 12:04 PM, Martin Liška wrote:
> 3) lookup_template_class_1
> 
> $ ./xg++ -B. 
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/template/ttp23.C -c 
> -fchecking=3
> hash table checking failed: equal operator returns true for a pair of values 
> with a different hash 
> value/home/marxin/Programming/gcc/gcc/testsuite/g++.dg/template/ttp23.C: In 
> instantiation of ‘struct B<A>’:
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/template/ttp23.C:15:8:   
> required from here
> /home/marxin/Programming/gcc/gcc/testsuite/g++.dg/template/ttp23.C:8:17: 
> internal compiler error: in find_slot_with_hash, at hash-table.h:905
>     8 |     friend bool foo (const B<Q>& a);
>       |                 ^~~
> 0xa265a4 hash_table<spec_hasher, 
> xcallocator>::find_slot_with_hash(spec_entry* const&, unsigned int, 
> insert_option)
>       /home/marxin/Programming/gcc/gcc/hash-table.h:905
> 0xa042ce lookup_template_class_1
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:9629
> 0xa042ce lookup_template_class(tree_node*, tree_node*, tree_node*, 
> tree_node*, int, int)
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:9674
> 0xa03670 tsubst_aggr_type
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:12679
> 0x9fefcd tsubst(tree_node*, tree_node*, int, tree_node*)
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:14294
> 0x9fe1a9 tsubst(tree_node*, tree_node*, int, tree_node*)
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:14285
> 0xa0d8bd tsubst_arg_types
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:13891
> 0xa0dc24 tsubst_function_type
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:14032
> 0x9fe790 tsubst(tree_node*, tree_node*, int, tree_node*)
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:14769
> 0x9f2c7c tsubst_function_decl
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:12921
> 0xa02d27 tsubst_template_decl
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:13214
> 0x9f4416 tsubst_decl
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:13316
> 0x9ff0ca tsubst(tree_node*, tree_node*, int, tree_node*)
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:14212
> 0xa1dfd0 tsubst_friend_function
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:10310
> 0xa1dfd0 instantiate_class_template_1
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:11359
> 0xa1dfd0 instantiate_class_template(tree_node*)
>       /home/marxin/Programming/gcc/gcc/cp/pt.c:11424
> 0xa66b22 complete_type(tree_node*)
>       /home/marxin/Programming/gcc/gcc/cp/typeck.c:138
> 0x9023c7 start_decl_1(tree_node*, bool)
>       /home/marxin/Programming/gcc/gcc/cp/decl.c:5278
> 0x92a15f start_decl(cp_declarator const*, cp_decl_specifier_seq*, int, 
> tree_node*, tree_node*, tree_node**)
>       /home/marxin/Programming/gcc/gcc/cp/decl.c:5241
> 0x9c1944 cp_parser_init_declarator
>       /home/marxin/Programming/gcc/gcc/cp/parser.c:19750

This one is about inconsistency between:

/* Returns a hash for a template TMPL and template arguments ARGS.  */

static hashval_t
hash_tmpl_and_args (tree tmpl, tree args)
{
  hashval_t val = iterative_hash_object (DECL_UID (tmpl), 0);
  return iterative_hash_template_arg (args, val);
}

iterative_hash_template_arg is problematic, differs from:
bool
spec_hasher::equal (spec_entry *e1, spec_entry *e2)
{
  int equal;

  ++comparing_specializations;
  equal = (e1->tmpl == e2->tmpl
           && comp_template_args (e1->args, e2->args));
...

where comp_template_args (e1->args, e2->args) returns true, but
iterative_hash_template_arg values are different.

Can please some C++ maintainer take a look?

Thanks,
Martin