On Thu, 8 Apr 2021, Marek Polacek via Gcc-patches wrote:
> When we have a member function with auto parameter like this:
>
> struct S {
> void f(auto);
> };
>
> cp_parser_member_declaration -> grokfield produces a FUNCTION_DECL
> "void S::foo(auto:1)", and then finish_fully_implicit_template turns
> that FUNCTION_DECL into a TEMPLATE_DECL. The bug here is that we only
> call cp_parser_save_default_args for a FUNCTION_DECL. As a consequence,
> abbrev10.C is rejected because we complain that the default argument has
> not been defined, and abbrev11.C ICEs, because we don't re-parse the
> delayed noexcept, so the DEFERRED_PARSE tree leaks into tsubst* where we
> crash. This patch fixes both issues.
>
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/10.4?
>
> gcc/cp/ChangeLog:
>
> PR c++/99806
> * parser.c (cp_parser_member_declaration): Call
> cp_parser_save_default_args even for function templates.
> (cp_parser_save_default_args): Extract the function declaration
> from a function template.
>
> gcc/testsuite/ChangeLog:
>
> PR c++/99806
> * g++.dg/concepts/abbrev10.C: New test.
> * g++.dg/concepts/abbrev11.C: New test.
> ---
> gcc/cp/parser.c | 8 +++++---
> gcc/testsuite/g++.dg/concepts/abbrev10.C | 18 ++++++++++++++++++
> gcc/testsuite/g++.dg/concepts/abbrev11.C | 10 ++++++++++
> 3 files changed, 33 insertions(+), 3 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/concepts/abbrev10.C
> create mode 100644 gcc/testsuite/g++.dg/concepts/abbrev11.C
>
> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index 59adac4492a..eef6bb3003e 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> @@ -26433,7 +26433,8 @@ cp_parser_member_declaration (cp_parser* parser)
> || !DECL_DECLARES_FUNCTION_P (decl))
> finish_member_declaration (decl);
>
> - if (TREE_CODE (decl) == FUNCTION_DECL)
> + if (TREE_CODE (decl) == FUNCTION_DECL
> + || DECL_FUNCTION_TEMPLATE_P (decl))
I guess you could use DECL_DECLARES_FUNCTION_P here.
> cp_parser_save_default_args (parser, decl);
> else if (TREE_CODE (decl) == FIELD_DECL
> && DECL_INITIAL (decl))
> @@ -30959,9 +30960,10 @@ cp_parser_late_parsing_for_member (cp_parser*
> parser, tree member_function)
> static void
> cp_parser_save_default_args (cp_parser* parser, tree decl)
> {
> - tree probe;
> + if (DECL_FUNCTION_TEMPLATE_P (decl))
> + decl = DECL_TEMPLATE_RESULT (decl);
Not sure if it'd be an improvement, but could use STRIP_TEMPLATE here
instead (or perhaps on the caller side).
>
> - for (probe = TYPE_ARG_TYPES (TREE_TYPE (decl));
> + for (tree probe = TYPE_ARG_TYPES (TREE_TYPE (decl));
> probe;
> probe = TREE_CHAIN (probe))
> if (TREE_PURPOSE (probe))
> diff --git a/gcc/testsuite/g++.dg/concepts/abbrev10.C
> b/gcc/testsuite/g++.dg/concepts/abbrev10.C
> new file mode 100644
> index 00000000000..b611346e926
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/concepts/abbrev10.C
> @@ -0,0 +1,18 @@
> +// PR c++/99806
> +// { dg-do compile { target c++14 } }
> +// { dg-additional-options "-fconcepts" }
> +
> +struct S {
> + void f(auto, auto, int = 3);
> + void f2(auto, auto, int = 3) { }
> + template<typename T> static T g(T, auto, int = 3);
> +};
> +
> +void
> +g ()
> +{
> + S::g(1, 2);
> + S s;
> + s.f(1, 2);
> + s.f2(1, 2);
> +}
> diff --git a/gcc/testsuite/g++.dg/concepts/abbrev11.C
> b/gcc/testsuite/g++.dg/concepts/abbrev11.C
> new file mode 100644
> index 00000000000..ddb479313df
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/concepts/abbrev11.C
> @@ -0,0 +1,10 @@
> +// PR c++/99806
> +// { dg-do compile { target c++14 } }
> +// { dg-additional-options "-fconcepts" }
> +
> +template <typename T> concept C = requires (T a) { a.f(0); };
> +struct S {
> + void f(auto) noexcept(B);
> + static constexpr bool B = true;
> +};
> +static_assert(C<S>, "");
>
> base-commit: 123b3e03c911a43054c1f88f5d3110e1d084dd4e
> --
> 2.30.2
>
>
