On 10/19/22 04:00, Jakub Jelinek wrote:
Hi!
We ICE on the following testcase during mangling, finish_compound_literal
returns for void{} void_node and the mangler doesn't handle it.
Handling void_node in the mangler seems problematic to me, because
we don't know for which case it has been created.
The following patch arranges to mangle just void{} the same as void()
if that is what we want to use, by doing what we do for void() when
processing void{}.
The code does that only if processing_template_decl, because otherwise
build_functional_cast will return void_node, so calling it looks like
wasted effort to me. But if you want to call it unconditionally,
I can certainly do that too.
I think in a template we want the same early-return behavior as in the
processing_template_decl block farther down in the function:
specifically, we want to return a CONSTRUCTOR (for which
COMPOUND_LITERAL_P is true), so it mangles as void{} rather than void().
Or do you want to mangle it differently? How?
clang++ doesn't support DR2351, so I can't check what they are doing.
Bootstrapped/regtested on x86_64-linux and i686-linux.
2022-10-19 Jakub Jelinek <ja...@redhat.com>
PR c++/106863
* semantics.cc (finish_compound_literal): For void{}, if
processing_template_decl return build_functional_cast of NULL_TREE
to VOID_TYPE rather than void_node.
* g++.dg/cpp0x/dr2351-2.C: New test.
--- gcc/cp/semantics.cc.jj 2022-10-10 09:31:57.410985121 +0200
+++ gcc/cp/semantics.cc 2022-10-18 15:24:08.726026118 +0200
@@ -3164,7 +3164,12 @@ finish_compound_literal (tree type, tree
{
/* DR2351 */
if (VOID_TYPE_P (type) && CONSTRUCTOR_NELTS (compound_literal) == 0)
- return void_node;
+ {
+ if (!processing_template_decl)
+ return void_node;
+ location_t loc = cp_expr_loc_or_input_loc (compound_literal);
+ return build_functional_cast (loc, type, NULL_TREE, complain);
+ }
else if (VOID_TYPE_P (type)
&& processing_template_decl
&& maybe_zero_constructor_nelts (compound_literal))
--- gcc/testsuite/g++.dg/cpp0x/dr2351-2.C.jj 2022-10-18 15:27:01.146690132
+0200
+++ gcc/testsuite/g++.dg/cpp0x/dr2351-2.C 2022-10-18 15:27:39.909164970
+0200
@@ -0,0 +1,16 @@
+// DR2351
+// { dg-do compile { target c++11 } }
+
+void bar (int);
+
+template <typename T>
+auto foo (T t) -> decltype (bar (t), void{})
+{
+ return bar (t);
+}
+
+int
+main ()
+{
+ foo (0);
+}
Jakub
