On Fri, 17 Jan 2025, Nathaniel Shead wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
>
> -- >8 --
>
> In the linked testcase, we're erroring because the declared return types
> of the functions do not appear to match. This is because when merging
> the deduced return types for 'foo' in 'auto-5_b.C', we overwrote the
> return type for the declaration with the deduced return type from
> 'auto-5_a.C' but neglected to track that we were originally declared
> with 'auto'.
Is this a regression caused by the PR114795 fix? Maybe we should
backport this.
>
> As a drive-by improvement to QOI, also add checks for if the deduced
> return types do not match; this is currently useful because we do not
> check the equivalence of the bodies of functions yet.
>
> PR c++/118049
>
> gcc/cp/ChangeLog:
>
> * module.cc (trees_in::is_matching_decl): Propagate
> FNDECL_USED_AUTO as well.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/modules/auto-5_a.C: New test.
> * g++.dg/modules/auto-5_b.C: New test.
> * g++.dg/modules/auto-5_c.C: New test.
> * g++.dg/modules/auto-6_a.H: New test.
> * g++.dg/modules/auto-6_b.C: New test.
>
> Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
> ---
> gcc/cp/module.cc | 5 +++++
> gcc/testsuite/g++.dg/modules/auto-5_a.C | 10 ++++++++++
> gcc/testsuite/g++.dg/modules/auto-5_b.C | 14 ++++++++++++++
> gcc/testsuite/g++.dg/modules/auto-5_c.C | 4 ++++
> gcc/testsuite/g++.dg/modules/auto-6_a.H | 5 +++++
> gcc/testsuite/g++.dg/modules/auto-6_b.C | 6 ++++++
> 6 files changed, 44 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/modules/auto-5_a.C
> create mode 100644 gcc/testsuite/g++.dg/modules/auto-5_b.C
> create mode 100644 gcc/testsuite/g++.dg/modules/auto-5_c.C
> create mode 100644 gcc/testsuite/g++.dg/modules/auto-6_a.H
> create mode 100644 gcc/testsuite/g++.dg/modules/auto-6_b.C
>
> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> index 61116fe7669..6fe64bb538c 100644
> --- a/gcc/cp/module.cc
> +++ b/gcc/cp/module.cc
> @@ -11902,8 +11902,13 @@ trees_in::is_matching_decl (tree existing, tree
> decl, bool is_typedef)
> {
> dump (dumper::MERGE)
> && dump ("Propagating deduced return type to %N", existing);
> + FNDECL_USED_AUTO (e_inner) = true;
> + DECL_SAVED_AUTO_RETURN_TYPE (existing) = TREE_TYPE (e_type);
> TREE_TYPE (existing) = change_return_type (TREE_TYPE (d_type),
> e_type);
> }
> + else if (type_uses_auto (d_ret)
> + && !same_type_p (TREE_TYPE (d_type), TREE_TYPE (e_type)))
> + goto mismatch;
> }
> else if (is_typedef)
> {
> diff --git a/gcc/testsuite/g++.dg/modules/auto-5_a.C
> b/gcc/testsuite/g++.dg/modules/auto-5_a.C
> new file mode 100644
> index 00000000000..fcab6f301e1
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/auto-5_a.C
> @@ -0,0 +1,10 @@
> +// PR c++/118049
> +// { dg-additional-options "-fmodules -Wno-global-module" }
> +// { dg-module-cmi A }
> +
> +module;
> +template <typename T> struct S {
> + auto foo() {}
> +};
> +export module A;
> +template struct S<char>;
> diff --git a/gcc/testsuite/g++.dg/modules/auto-5_b.C
> b/gcc/testsuite/g++.dg/modules/auto-5_b.C
> new file mode 100644
> index 00000000000..f75ed2d0f0c
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/auto-5_b.C
> @@ -0,0 +1,14 @@
> +// PR c++/118049
> +// { dg-additional-options "-fmodules -Wno-global-module" }
> +// { dg-module-cmi B }
> +
> +module;
> +template <typename T> struct S {
> + auto foo() {}
> +};
> +template struct S<char>;
> +export module B;
> +import A;
> +template <typename> void x() {
> + S<char>{}.foo();
> +}
> diff --git a/gcc/testsuite/g++.dg/modules/auto-5_c.C
> b/gcc/testsuite/g++.dg/modules/auto-5_c.C
> new file mode 100644
> index 00000000000..f351c2b1ae4
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/auto-5_c.C
> @@ -0,0 +1,4 @@
> +// PR c++/118049
> +// { dg-additional-options "-fmodules -fno-module-lazy
> -fdump-lang-module-alias" }
> +
> +import B;
> diff --git a/gcc/testsuite/g++.dg/modules/auto-6_a.H
> b/gcc/testsuite/g++.dg/modules/auto-6_a.H
> new file mode 100644
> index 00000000000..3ad08ab81ce
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/auto-6_a.H
> @@ -0,0 +1,5 @@
> +// { dg-additional-options "-fmodule-header" }
> +
> +inline auto foo() {
> + return 1;
> +}
> diff --git a/gcc/testsuite/g++.dg/modules/auto-6_b.C
> b/gcc/testsuite/g++.dg/modules/auto-6_b.C
> new file mode 100644
> index 00000000000..aab7be4e530
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/auto-6_b.C
> @@ -0,0 +1,6 @@
> +// { dg-additional-options "-fmodules-ts -fno-module-lazy" }
> +
> +inline auto foo() { // { dg-error "conflicting" }
> + return 1.0;
> +}
> +import "auto-6_a.H";
> --
> 2.47.0
>
>
