https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103769
--- Comment #6 from Sergei Trofimovich <slyfox at gcc dot gnu.org> ---
Trying to understand what the error means:
Crash happens when we look up entry in
gcc/cp/pt.c:static GTY (()) spec_hash_table *type_specializations;
It's a hash table of entries of spec_entry type:
struct GTY((for_user)) spec_entry
{
tree tmpl; /* The general template this is a specialization of. */
tree args; /* The args for this (maybe-partial) specialization. */
tree spec; /* The specialization itself. */
};
spec_hasher type defines both hasher and equality. hash is defined on fields
'tmpl' and 'args', equality is defined on 'tmpl', 'args' and sometimes 'spec':
bool
spec_hasher::equal (spec_entry *e1, spec_entry *e2)
{
int equal;
++comparing_specializations;
++comparing_dependent_aliases;
++processing_template_decl;
equal = (e1->tmpl == e2->tmpl
&& comp_template_args (e1->args, e2->args));
if (equal && flag_concepts
/* tmpl could be a FIELD_DECL for a capture pack. */
&& TREE_CODE (e1->tmpl) == TEMPLATE_DECL
&& VAR_P (DECL_TEMPLATE_RESULT (e1->tmpl))
&& uses_template_parms (e1->args))
{
/* Partial specializations of a variable template can be distinguished by
constraints. */
tree c1 = e1->spec ? get_constraints (e1->spec) : NULL_TREE;
tree c2 = e2->spec ? get_constraints (e2->spec) : NULL_TREE;
equal = equivalent_constraints (c1, c2);
}
--processing_template_decl;
--comparing_dependent_aliases;
--comparing_specializations;
return equal;
}
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);
}
hashval_t
spec_hasher::hash (spec_entry *e)
{
return hash_tmpl_and_args (e->tmpl, e->args);
}
How can hash differ when values match?
