On 2/17/26 3:04 PM, Jakub Jelinek wrote:
Hi!
The following testcase ICEs in C++ 20 and older, because during
diagnostics dump_template_bindings attempts to tsubst with tf_none
something and we try to emit a pedwarn during that.
While the pedwarn could be just guarded with if (complain & tf_warning),
I thought we shouldn't support extensions for tf_none and should
instead return error_mark_node.
The following patch does that.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
OK.
2026-02-17 Jakub Jelinek <[email protected]>
PR c++/120685
* typeck2.cc (build_functional_cast_1): For C++23 auto(x)
without tf_warning or tf_error return error_mark_node instead of
emitting pedwarn and handling it.
* semantics.cc (finish_compound_literal): Similarly for C++26
auto{x}.
* g++.dg/cpp23/auto-fncast19.C: New test.
--- gcc/cp/typeck2.cc.jj 2026-02-06 11:18:47.091639968 +0100
+++ gcc/cp/typeck2.cc 2026-02-16 11:27:50.385010224 +0100
@@ -2610,9 +2610,13 @@ build_functional_cast_1 (location_t loc,
return error_mark_node;
}
else if (cxx_dialect < cxx23)
- pedwarn (loc, OPT_Wc__23_extensions,
- "%<auto(x)%> only available with "
- "%<-std=c++23%> or %<-std=gnu++23%>");
+ {
+ if ((complain & tf_warning_or_error) == 0)
+ return error_mark_node;
+ pedwarn (loc, OPT_Wc__23_extensions,
+ "%<auto(x)%> only available with "
+ "%<-std=c++23%> or %<-std=gnu++23%>");
+ }
}
else
{
--- gcc/cp/semantics.cc.jj 2026-02-12 18:49:18.465869495 +0100
+++ gcc/cp/semantics.cc 2026-02-16 11:28:28.803359539 +0100
@@ -3874,9 +3874,13 @@ finish_compound_literal (tree type, tree
return error_mark_node;
}
else if (cxx_dialect < cxx23)
- pedwarn (input_location, OPT_Wc__23_extensions,
- "%<auto{x}%> only available with "
- "%<-std=c++23%> or %<-std=gnu++23%>");
+ {
+ if ((complain & tf_warning_or_error) == 0)
+ return error_mark_node;
+ pedwarn (input_location, OPT_Wc__23_extensions,
+ "%<auto{x}%> only available with "
+ "%<-std=c++23%> or %<-std=gnu++23%>");
+ }
type = do_auto_deduction (type, compound_literal, type, complain,
adc_variable_type);
if (type == error_mark_node)
--- gcc/testsuite/g++.dg/cpp23/auto-fncast19.C.jj 2026-02-16
11:43:24.524190997 +0100
+++ gcc/testsuite/g++.dg/cpp23/auto-fncast19.C 2026-02-16 11:42:24.750203226
+0100
@@ -0,0 +1,12 @@
+// PR c++/120685
+// { dg-do compile { target c++11 } }
+// { dg-options "" }
+
+template <typename T>
+void foo (decltype (auto (T ())) x) {} // { dg-warning "'auto\\\(x\\\)' only available
with" "" { target c++20_down } }
+
+int
+main ()
+{
+ foo <int> (1); // { dg-error "no matching function for call to
'foo<int>\\\(int\\\)'" "" { target c++20_down } }
+}
Jakub
