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c++: Fix comparison of fn() and ns::fn() [PR90711]

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The resolution of CWG issue 1321 clarified that when deciding whether two
expressions involving template parameters are equivalent, two dependent
function calls where the function is named with an unqualified-id are
considered to be equivalent if the name is the same, even if unqualified
lookup finds different sets of functions.  We were wrongly treating
qualified-ids the same way, so that EXISTS and test::EXISTS were considered
to be equivalent even though they are looking up the name in different
scopes.  This also causes a mangling bug, but I don't think it's safe to fix
that for GCC 10; this patch just fixes the comparison.

gcc/cp/ChangeLog
2020-03-30  Jason Merrill  <jason@redhat.com>

	PR c++/90711
	* tree.c (cp_tree_equal) [CALL_EXPR]: Compare KOENIG_LOOKUP_P.
	(called_fns_equal): Check DECL_CONTEXT.
This commit is contained in:
Jason Merrill 2020-03-30 16:09:43 -04:00
parent 1cb1986cb5
commit 5830f75355
3 changed files with 57 additions and 1 deletions
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6
gcc/cp/ChangeLog
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@ -1,3 +1,9 @@
2020-03-30 Jason Merrill <jason@redhat.com>
PR c++/90711
* tree.c (cp_tree_equal) [CALL_EXPR]: Compare KOENIG_LOOKUP_P.
(called_fns_equal): Check DECL_CONTEXT.
2020-03-30 Jakub Jelinek <jakub@redhat.com>
PR c++/94385

14
gcc/cp/tree.c
View File

@ -2464,6 +2464,8 @@ is_overloaded_fn (tree x)
tree
dependent_name (tree x)
{
/* FIXME a dependent name must be unqualified, but this function doesn't
distinguish between qualified and unqualified identifiers. */
if (identifier_p (x))
return x;
if (TREE_CODE (x) == TEMPLATE_ID_EXPR)
@ -3581,6 +3583,15 @@ called_fns_equal (tree t1, tree t2)
if (name1 != name2)
return false;
/* FIXME dependent_name currently returns an unqualified name regardless
of whether the function was named with a qualified- or unqualified-id.
Until that's fixed, check that we aren't looking at overload sets from
different scopes. */
if (is_overloaded_fn (t1) && is_overloaded_fn (t2)
&& (DECL_CONTEXT (get_first_fn (t1))
!= DECL_CONTEXT (get_first_fn (t2))))
return false;
if (TREE_CODE (t1) == TEMPLATE_ID_EXPR)
targs1 = TREE_OPERAND (t1, 1);
if (TREE_CODE (t2) == TEMPLATE_ID_EXPR)
@ -3677,7 +3688,8 @@ cp_tree_equal (tree t1, tree t2)
{
tree arg1, arg2;
call_expr_arg_iterator iter1, iter2;
if (!called_fns_equal (CALL_EXPR_FN (t1), CALL_EXPR_FN (t2)))
if (KOENIG_LOOKUP_P (t1) != KOENIG_LOOKUP_P (t2)
|| !called_fns_equal (CALL_EXPR_FN (t1), CALL_EXPR_FN (t2)))
return false;
for (arg1 = first_call_expr_arg (t1, &iter1),
arg2 = first_call_expr_arg (t2, &iter2);

38
gcc/testsuite/g++.dg/template/dependent-name14.C Normal file
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@ -0,0 +1,38 @@
// PR c++/90711
// { dg-do compile { target c++11 } }
namespace test {
void EXISTS(int);
}
template<typename... ARGS>
struct stub_void {
typedef void type;
};
template<typename... ARGS>
using stub_void_t = typename stub_void<ARGS...>::type;
#if !defined(SUPPRESS)
template<typename O, typename = void>
struct has_to_string {
static constexpr bool value = false;
};
template<typename O>
struct has_to_string<O, stub_void_t<decltype(EXISTS(O{}))>> {
static constexpr bool value = true;
};
#endif
template<typename O, typename = void>
struct has_std_to_string {
static constexpr bool value = false;
};
template<typename O>
struct has_std_to_string<O, stub_void_t<decltype(test::EXISTS(O{}))>> {
static constexpr bool value = true;
};
static_assert (has_std_to_string<int>::value, "");