https://gcc.gnu.org/g:5f75fc37b131c701a5b5c627239fa4e4dfabe230
commit r16-7358-g5f75fc37b131c701a5b5c627239fa4e4dfabe230 Author: Jakub Jelinek <[email protected]> Date: Fri Feb 6 11:27:52 2026 +0100 tree: Fix up build_function_type for (...) fntypes [PR123977] The following testcase ICEs in -std=c++26 mode since my r16-4338 C++26 va_start changes. The problem is that if we have anything non-canonical in a function type with (...) in C++26 (or C23/C2Y) mode, in this case the R typedef on return type rather than void, then we try to build TYPE_CANONICAL for that, but weren't passing in the no_named_args_stdarg_p, so a type with TYPE_NO_NAMED_ARGS_STDARG_P flag set got TYPE_CANONICAL with TYPE_NO_NAMED_ARGS_STDARG_P flag cleared and comptypes then didn't like that as those aren't really compatible types (...) vs. the C89-ish () which even C++ uses for some type-generic etc. builtins. 2026-02-05 Jakub Jelinek <[email protected]> PR c++/123977 * tree.cc (build_function_type): Pass no_named_args_stdarg_p as last argument to recursive call. * g++.dg/cpp26/stdarg10.C: New test. Diff: --- gcc/testsuite/g++.dg/cpp26/stdarg10.C | 19 +++++++++++++++++++ gcc/tree.cc | 3 ++- 2 files changed, 21 insertions(+), 1 deletion(-) diff --git a/gcc/testsuite/g++.dg/cpp26/stdarg10.C b/gcc/testsuite/g++.dg/cpp26/stdarg10.C new file mode 100644 index 000000000000..a8e1ddaee1e8 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp26/stdarg10.C @@ -0,0 +1,19 @@ +// PR c++/123977 +// { dg-do compile } + +typedef void R; +struct A { + R foo (...) const volatile; + void foo (); +}; + +template <class T> +struct B { + static void bar () { (T (A::*)) &A::foo; } +}; + +void +baz () +{ + B <R (...) const volatile>::bar; +} diff --git a/gcc/tree.cc b/gcc/tree.cc index cf47f0ee64da..22effa6bcd19 100644 --- a/gcc/tree.cc +++ b/gcc/tree.cc @@ -7780,7 +7780,8 @@ build_function_type (tree value_type, tree arg_types, gcc_assert (TYPE_STRUCTURAL_EQUALITY_P (t)); else if (any_noncanonical_p) TYPE_CANONICAL (t) = build_function_type (TYPE_CANONICAL (value_type), - canon_argtypes); + canon_argtypes, + no_named_args_stdarg_p); if (!COMPLETE_TYPE_P (t)) layout_type (t);
