[v2] c++/modules: Differentiate extern templates and TYPE_DECL_SUPPRESS_DEBUG [PR112820]
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Commit Message
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 <nathanieloshead@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
Comments
On Mon, Jan 8, 2024 at 10:58 AM Nathaniel Shead
<nathanieloshead@gmail.com> 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?
OK if C++ folks are fine.
Richard.
> -- >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 <nathanieloshead@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. */
> #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
>
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 <nathanieloshead@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
>
>
On 1/8/24 10:27, Patrick Palka wrote:
> 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:
>>>>
>>>> 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.
But a vtable isn't a TYPE_DECL?
I suspect what you mean is that maybe_suppress_debug_info is setting
TYPE_DECL_SUPPRESS_DEBUG to try to avoid duplication of debug info for
classes with vtables, and then the modules code is wrongly assuming that
you can check DECL_EXTERNAL for TYPE_DECL, and that it's set only if
CLASSTYPE_INTERFACE_ONLY is also set, which is wrong in this case, so we
avoid emitting the vtable or anything else for that class.
It seems unnecessary to start setting DECL_EXTERNAL on the TYPE_DECL to
mean the exact same thing as CLASSTYPE_INTERFACE_ONLY. Rather, the
modules code should stop trying to check DECL_EXTERNAL on a TYPE_DECL.
Under what circumstances does it make sense for CLASSTYPE_INTERFACE_ONLY
to be set in the context of modules, anyway? We probably want to
propagate it for things in the global module so that various libstdc++
explicit instantiations work the same with import std.
For an class imported from a named module, this ties into the earlier
discussion about vtables and inlines that hasn't resolved yet in the ABI
committee. But it's certainly significantly interface-like. And I
would expect maybe_suppress_debug_info to suppress the debug info for
such a class on the assumption that the module unit has the needed debug
info.
Jason
On Mon, Jan 15, 2024 at 06:10:55PM -0500, Jason Merrill wrote:
> On 1/8/24 10:27, Patrick Palka wrote:
> > 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:
> > > > >
> > > > > 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.
>
> But a vtable isn't a TYPE_DECL?
>
> I suspect what you mean is that maybe_suppress_debug_info is setting
> TYPE_DECL_SUPPRESS_DEBUG to try to avoid duplication of debug info for
> classes with vtables, and then the modules code is wrongly assuming that you
> can check DECL_EXTERNAL for TYPE_DECL, and that it's set only if
> CLASSTYPE_INTERFACE_ONLY is also set, which is wrong in this case, so we
> avoid emitting the vtable or anything else for that class.
>
Ah, right; I definitely misread what was going on.
> It seems unnecessary to start setting DECL_EXTERNAL on the TYPE_DECL to mean
> the exact same thing as CLASSTYPE_INTERFACE_ONLY. Rather, the modules code
> should stop trying to check DECL_EXTERNAL on a TYPE_DECL.
>
> Under what circumstances does it make sense for CLASSTYPE_INTERFACE_ONLY to
> be set in the context of modules, anyway? We probably want to propagate it
> for things in the global module so that various libstdc++ explicit
> instantiations work the same with import std.
>
> For an class imported from a named module, this ties into the earlier
> discussion about vtables and inlines that hasn't resolved yet in the ABI
> committee. But it's certainly significantly interface-like. And I would
> expect maybe_suppress_debug_info to suppress the debug info for such a class
> on the assumption that the module unit has the needed debug info.
>
> Jason
>
I didn't consider messing with 'CLASSTYPE_INTERFACE_ONLY' because the
modules code currently always sets 'lang->interface_unknown = true' on
read with the comment "Redetermine interface". But I see now as well
this comment:
// Interfaceness is recalculated upon reading. May have to revisit?
// How do dllexport and dllimport interact across a module?
// lang->interface_only
// lang->interface_unknown
So it seems reasonable to reconsider this now. I hadn't considered
declarations in the GMF but I think you're right that we'll want to
propagate it; I guess in general things in the GMF should try to behave
as close to how they would have if they were #included directly in the
importing TU.
I suspect this fix will be more involved but I'll try to wrap my head
around it and see what I can come up with.
@@ -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)
{
new file mode 100644
@@ -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;
+};
new file mode 100644
@@ -0,0 +1,8 @@
+// PR c++/112820
+// { dg-additional-options "-fmodules-ts -g" }
+
+module io;
+
+const char* error::what() const noexcept {
+ return "bla";
+}
new file mode 100644
@@ -0,0 +1,9 @@
+// PR c++/112820
+// { dg-module-do link }
+// { dg-additional-options "-fmodules-ts -g" }
+
+import io;
+
+int main() {
+ error{};
+}
new file mode 100644
@@ -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;
+};
new file mode 100644
@@ -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{};
+}
@@ -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. */
@@ -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. */
#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. */