On Mon, 8 Jan 2024, Nathaniel Shead wrote:
> On Thu, Jan 04, 2024 at 03:39:15PM -0500, Patrick Palka wrote:
> > 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.
> >
>
> That seems like a good idea, thanks. How does this look?
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
>
> -- >8 --
>
> Currently, DECL_EXTERNAL and TYPE_DECL_SUPPRESS_DEBUG share a bit. This
> causes issues with module code, which then incorrectly assumes that
> anything with suppressed debug info (such as vtables when '-g' is
> specified) is an extern template and thus prevents their emission.
>
> This patch splits the two flags up; extern templates continue to use the
> DECL_EXTERNAL flag (and the documentation is updated to indicate this),
> but TYPE_DECL_SUPPRESS_DEBUG now uses the 'decl_not_flexarray' flag,
> which currently is only used by FIELD_DECLs.
>
> PR c++/112820
> PR c++/102607
>
> gcc/cp/ChangeLog:
>
> * pt.cc (mark_class_instantiated): Set DECL_EXTERNAL explicitly.
>
> gcc/ChangeLog:
>
> * tree-core.h (struct tree_decl_common): Update comments.
> * tree.h (DECL_EXTERNAL): Update comments.
> (TYPE_DECL_SUPPRESS_DEBUG): Use 'decl_not_flexarray' instead.
>
> 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/pt.cc | 1 +
> 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 +++++++++
> gcc/tree-core.h | 6 +++---
> gcc/tree.h | 8 ++++----
> 8 files changed, 51 insertions(+), 7 deletions(-)
> 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/pt.cc b/gcc/cp/pt.cc
> index e38e7a773f0..7839745035b 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -26256,6 +26256,7 @@ mark_class_instantiated (tree t, int extern_p)
> SET_CLASSTYPE_EXPLICIT_INSTANTIATION (t);
> SET_CLASSTYPE_INTERFACE_KNOWN (t);
> CLASSTYPE_INTERFACE_ONLY (t) = extern_p;
> + DECL_EXTERNAL (TYPE_NAME (t)) = extern_p;
> TYPE_DECL_SUPPRESS_DEBUG (TYPE_NAME (t)) = extern_p;
> if (! extern_p)
> {
> 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{};
> +}
> diff --git a/gcc/tree-core.h b/gcc/tree-core.h
> index 8a89462bd7e..1ca4d4c07bd 100644
> --- a/gcc/tree-core.h
> +++ b/gcc/tree-core.h
> @@ -1814,8 +1814,7 @@ struct GTY(()) tree_decl_common {
> In FIELD_DECL, this is DECL_FIELD_ABI_IGNORED. */
> unsigned decl_flag_0 : 1;
> /* In FIELD_DECL, this is DECL_BIT_FIELD
> - In VAR_DECL and FUNCTION_DECL, this is DECL_EXTERNAL.
> - In TYPE_DECL, this is TYPE_DECL_SUPPRESS_DEBUG. */
> + In VAR_DECL, FUNCTION_DECL, and TYPE_DECL, this is DECL_EXTERNAL. */
> unsigned decl_flag_1 : 1;
> /* In FIELD_DECL, this is DECL_NONADDRESSABLE_P
> In VAR_DECL, PARM_DECL and RESULT_DECL, this is
> @@ -1845,7 +1844,8 @@ struct GTY(()) tree_decl_common {
> TYPE_WARN_IF_NOT_ALIGN. */
> unsigned int warn_if_not_align : 6;
>
> - /* In FIELD_DECL, this is DECL_NOT_FLEXARRAY. */
> + /* In FIELD_DECL, this is DECL_NOT_FLEXARRAY.
> + In TYPE_DECL, this is TYPE_DECL_SUPPRESS_DEBUG. */
> unsigned int decl_not_flexarray : 1;
>
> /* 5 bits unused. */
> diff --git a/gcc/tree.h b/gcc/tree.h
> index 972a067a1f7..8bdc471ad4e 100644
> --- a/gcc/tree.h
> +++ b/gcc/tree.h
> @@ -2848,9 +2848,9 @@ extern tree vector_element_bits_tree (const_tree);
> #define DECL_LANG_SPECIFIC(NODE) \
> (DECL_COMMON_CHECK (NODE)->decl_common.lang_specific)
>
> -/* In a VAR_DECL or FUNCTION_DECL, nonzero means external reference:
> - do not allocate storage, and refer to a definition elsewhere. Note that
> - this does not necessarily imply the entity represented by NODE
> +/* In a VAR_DECL, FUNCTION_DECL, or TYPE_DECL, nonzero means external
> + reference: do not allocate storage, and refer to a definition elsewhere.
> + Note that this does not necessarily imply the entity represented by NODE
> has no program source-level definition in this translation unit. For
> example, for a FUNCTION_DECL, DECL_SAVED_TREE may be non-NULL and
> DECL_EXTERNAL may be true simultaneously; that can be the case for
> @@ -3553,7 +3553,7 @@ extern vec<tree, va_gc> **decl_debug_args_insert (tree);
> into stabs. Instead it will generate cross reference ('x') of names.
> This uses the same flag as DECL_EXTERNAL. */
I guess this last sentence should be removed since it's no longer true,
LGTM otherwise, thanks!
> #define TYPE_DECL_SUPPRESS_DEBUG(NODE) \
> - (TYPE_DECL_CHECK (NODE)->decl_common.decl_flag_1)
> + (TYPE_DECL_CHECK (NODE)->decl_common.decl_not_flexarray)
>
> /* Getter of the imported declaration associated to the
> IMPORTED_DECL node. */
> --
> 2.43.0
>
>
