On Sun, 3 Dec 2023, Nathaniel Shead wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
>
> -- >8 --
>
> The TYPE_DECL_SUPPRESS_DEBUG and DECL_EXTERNAL flags use the same
> underlying bit. This is causing confusion when attempting to determine
> the interface for a streamed-in class type, since the modules code
> currently assumes that all DECL_EXTERNAL types are extern templates.
> However, when -g is specified then TYPE_DECL_SUPPRESS_DEBUG (and hence
> DECL_EXTERNAL) is marked on various other kinds of declarations, such as
> vtables, which causes them to never be emitted.
Good catch.. Maybe we should use different bits for these flags? I wouldn't be
surprised if this bit sharing causes issues elsewhere in the compiler. The
documentation in tree.h / tree-core.h says DECL_EXTERNAL is only valid for
VAR_DECL and FUNCTION_DECL, so at one point it was safe to share the same bit
but that's not true anymore it seems.
Looking at tree-core.h:tree_decl_common luckily we have plenty of spare bits.
We could also e.g. make TYPE_DECL_SUPPRESS_DEBUG use the decl_not_flexarray bit
which is otherwise only used for FIELD_DECL.
>
> This patch constrains the checks for DECL_EXTERNAL for this to only
> consider template instantiations, thus avoiding the issue.
>
> PR c++/102607
> PR c++/112820
>
> gcc/cp/ChangeLog:
>
> * module.cc (trees_in::read_class_def): Only set interface for
> template instantiations.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/modules/debug-2_a.C: New test.
> * g++.dg/modules/debug-2_b.C: New test.
> * g++.dg/modules/debug-2_c.C: New test.
> * g++.dg/modules/debug-3_a.C: New test.
> * g++.dg/modules/debug-3_b.C: New test.
>
> Signed-off-by: Nathaniel Shead <nathanielosh...@gmail.com>
> ---
> gcc/cp/module.cc | 4 +++-
> gcc/testsuite/g++.dg/modules/debug-2_a.C | 9 +++++++++
> gcc/testsuite/g++.dg/modules/debug-2_b.C | 8 ++++++++
> gcc/testsuite/g++.dg/modules/debug-2_c.C | 9 +++++++++
> gcc/testsuite/g++.dg/modules/debug-3_a.C | 8 ++++++++
> gcc/testsuite/g++.dg/modules/debug-3_b.C | 9 +++++++++
> 6 files changed, 46 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/modules/debug-2_a.C
> create mode 100644 gcc/testsuite/g++.dg/modules/debug-2_b.C
> create mode 100644 gcc/testsuite/g++.dg/modules/debug-2_c.C
> create mode 100644 gcc/testsuite/g++.dg/modules/debug-3_a.C
> create mode 100644 gcc/testsuite/g++.dg/modules/debug-3_b.C
>
> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> index 33fcf396875..257f39421d0 100644
> --- a/gcc/cp/module.cc
> +++ b/gcc/cp/module.cc
> @@ -12041,7 +12041,9 @@ trees_in::read_class_def (tree defn, tree
> maybe_template)
> bool installing = maybe_dup && !TYPE_SIZE (type);
> if (installing)
> {
> - if (DECL_EXTERNAL (defn) && TYPE_LANG_SPECIFIC (type))
> + if (DECL_EXTERNAL (defn)
> + && TYPE_LANG_SPECIFIC (type)
> + && CLASSTYPE_TEMPLATE_INSTANTIATION (type))
> {
> /* We don't deal with not-really-extern, because, for a
> module you want the import to be the interface, and for a
> diff --git a/gcc/testsuite/g++.dg/modules/debug-2_a.C
> b/gcc/testsuite/g++.dg/modules/debug-2_a.C
> new file mode 100644
> index 00000000000..eed0905542b
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/debug-2_a.C
> @@ -0,0 +1,9 @@
> +// PR c++/112820
> +// { dg-additional-options "-fmodules-ts -g" }
> +// { dg-module-cmi io }
> +
> +export module io;
> +
> +export struct error {
> + virtual const char* what() const noexcept;
> +};
> diff --git a/gcc/testsuite/g++.dg/modules/debug-2_b.C
> b/gcc/testsuite/g++.dg/modules/debug-2_b.C
> new file mode 100644
> index 00000000000..fc9afbc02e0
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/debug-2_b.C
> @@ -0,0 +1,8 @@
> +// PR c++/112820
> +// { dg-additional-options "-fmodules-ts -g" }
> +
> +module io;
> +
> +const char* error::what() const noexcept {
> + return "bla";
> +}
> diff --git a/gcc/testsuite/g++.dg/modules/debug-2_c.C
> b/gcc/testsuite/g++.dg/modules/debug-2_c.C
> new file mode 100644
> index 00000000000..37117f69dcd
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/debug-2_c.C
> @@ -0,0 +1,9 @@
> +// PR c++/112820
> +// { dg-module-do link }
> +// { dg-additional-options "-fmodules-ts -g" }
> +
> +import io;
> +
> +int main() {
> + error{};
> +}
> diff --git a/gcc/testsuite/g++.dg/modules/debug-3_a.C
> b/gcc/testsuite/g++.dg/modules/debug-3_a.C
> new file mode 100644
> index 00000000000..9e33d8260fd
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/debug-3_a.C
> @@ -0,0 +1,8 @@
> +// PR c++/102607
> +// { dg-additional-options "-fmodules-ts -g" }
> +// { dg-module-cmi mod }
> +
> +export module mod;
> +export struct B {
> + virtual ~B() = default;
> +};
> diff --git a/gcc/testsuite/g++.dg/modules/debug-3_b.C
> b/gcc/testsuite/g++.dg/modules/debug-3_b.C
> new file mode 100644
> index 00000000000..03c78b71b5d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/debug-3_b.C
> @@ -0,0 +1,9 @@
> +// PR c++/102607
> +// { dg-module-do link }
> +// { dg-additional-options "-fmodules-ts -g" }
> +
> +import mod;
> +int main() {
> + struct D : B {};
> + (void)D{};
> +}
> --
> 2.42.0
>
>
