diff mbox series

c++/modules: Only mark namespace-scope entities as exported [PR124781]

Message ID adJkz7LoEuf_78_o@Thaum.localdomain
State Committed
Commit c396fcf5ad4ad022b2b0638d7f1f80324d713458
Headers
Series c++/modules: Only mark namespace-scope entities as exported [PR124781] |

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Commit Message

Nathaniel Shead April 5, 2026, 1:34 p.m. UTC 
  Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk/15?

-- >8 --

We call 'set_originating_module' before we call pushdecl, which means
that for function-scope entities we might not have set DECL_CONTEXT yet.
Usually this doesn't matter, we only look at DECL_MODULE_EXPORT/ATTACH_P
on namespace-scope entities to begin with, but in the case in the linked
PR it causes issues because declarations in an unevaluated lambda appear
to be in an internal context.

Fixed by only considering non-null DECL_CONTEXT as being namespace scope
within set_originating_module.

As a drive-by improvement, ensured that we only talk about unnamed
namespaces in the diagnostic within check_module_decl_linkage if we're
actually within an anonymous namespace; this should be equivalent but
will lead to a slightly clearer diagnostic if a similar bug crops up
again later.

	PR c++/124781

gcc/cp/ChangeLog:

	* module.cc (set_originating_module): Add a function comment,
	only set attachment/exporting for entities with non-NULL
	DECL_CONTEXT.
	(check_module_decl_linkage): Use decl_anon_ns_mem_p instead of
	decl_internal_context_p.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/export-7.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---
 gcc/cp/module.cc                        | 10 ++++++++--
 gcc/testsuite/g++.dg/modules/export-7.C | 10 ++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/export-7.C

Comments

Jason Merrill April 6, 2026, 4:43 p.m. UTC | #1 
On 4/5/26 9:34 AM, Nathaniel Shead wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk/15?

OK.

> -- >8 --
> 
> We call 'set_originating_module' before we call pushdecl, which means
> that for function-scope entities we might not have set DECL_CONTEXT yet.
> Usually this doesn't matter, we only look at DECL_MODULE_EXPORT/ATTACH_P
> on namespace-scope entities to begin with, but in the case in the linked
> PR it causes issues because declarations in an unevaluated lambda appear
> to be in an internal context.
> 
> Fixed by only considering non-null DECL_CONTEXT as being namespace scope
> within set_originating_module.
> 
> As a drive-by improvement, ensured that we only talk about unnamed
> namespaces in the diagnostic within check_module_decl_linkage if we're
> actually within an anonymous namespace; this should be equivalent but
> will lead to a slightly clearer diagnostic if a similar bug crops up
> again later.
> 
> 	PR c++/124781
> 
> gcc/cp/ChangeLog:
> 
> 	* module.cc (set_originating_module): Add a function comment,
> 	only set attachment/exporting for entities with non-NULL
> 	DECL_CONTEXT.
> 	(check_module_decl_linkage): Use decl_anon_ns_mem_p instead of
> 	decl_internal_context_p.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/export-7.C: New test.
> 
> Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
> ---
>   gcc/cp/module.cc                        | 10 ++++++++--
>   gcc/testsuite/g++.dg/modules/export-7.C | 10 ++++++++++
>   2 files changed, 18 insertions(+), 2 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/modules/export-7.C
> 
> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> index 6958388e454..a8517569a1b 100644
> --- a/gcc/cp/module.cc
> +++ b/gcc/cp/module.cc
> @@ -22076,12 +22076,18 @@ set_defining_module_for_partial_spec (tree decl)
>       vec_safe_push (partial_specializations, decl);
>   }
>   
> +/* Record that DECL is declared in this TU, and note attachment and
> +   exporting for namespace-scope entities.  FRIEND_P is true if
> +   this is a friend declaration.  */
> +
>   void
>   set_originating_module (tree decl, bool friend_p ATTRIBUTE_UNUSED)
>   {
>     set_instantiating_module (decl);
>   
> -  if (!DECL_NAMESPACE_SCOPE_P (decl))
> +  /* DECL_CONTEXT may not be set yet when we're called for
> +     non-namespace-scope entities.  */
> +  if (!DECL_CONTEXT (decl) || !DECL_NAMESPACE_SCOPE_P (decl))
>       return;
>   
>     gcc_checking_assert (friend_p || decl == get_originating_module_decl (decl));
> @@ -22134,7 +22140,7 @@ check_module_decl_linkage (tree decl)
>   	 internal namespace as exporting a declaration with internal
>   	 linkage, as this would also implicitly export the internal
>   	 linkage namespace.  */
> -      if (decl_internal_context_p (decl))
> +      if (decl_anon_ns_mem_p (decl))
>   	{
>   	  error_at (DECL_SOURCE_LOCATION (decl),
>   		    "exporting declaration %qD declared in unnamed namespace",
> diff --git a/gcc/testsuite/g++.dg/modules/export-7.C b/gcc/testsuite/g++.dg/modules/export-7.C
> new file mode 100644
> index 00000000000..11001390d17
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/export-7.C
> @@ -0,0 +1,10 @@
> +// PR c++/124781
> +// { dg-do compile { target c++20 } }
> +// { dg-additional-options "-fmodules" }
> +// { dg-module-cmi foo }
> +
> +export module foo;
> +export using xx = decltype([] {
> +  using yy = int;
> +  int abc = 123;
> +}());
diff mbox series

Patch

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 6958388e454..a8517569a1b 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -22076,12 +22076,18 @@  set_defining_module_for_partial_spec (tree decl)
     vec_safe_push (partial_specializations, decl);
 }
 
+/* Record that DECL is declared in this TU, and note attachment and
+   exporting for namespace-scope entities.  FRIEND_P is true if
+   this is a friend declaration.  */
+
 void
 set_originating_module (tree decl, bool friend_p ATTRIBUTE_UNUSED)
 {
   set_instantiating_module (decl);
 
-  if (!DECL_NAMESPACE_SCOPE_P (decl))
+  /* DECL_CONTEXT may not be set yet when we're called for
+     non-namespace-scope entities.  */
+  if (!DECL_CONTEXT (decl) || !DECL_NAMESPACE_SCOPE_P (decl))
     return;
 
   gcc_checking_assert (friend_p || decl == get_originating_module_decl (decl));
@@ -22134,7 +22140,7 @@  check_module_decl_linkage (tree decl)
 	 internal namespace as exporting a declaration with internal
 	 linkage, as this would also implicitly export the internal
 	 linkage namespace.  */
-      if (decl_internal_context_p (decl))
+      if (decl_anon_ns_mem_p (decl))
 	{
 	  error_at (DECL_SOURCE_LOCATION (decl),
 		    "exporting declaration %qD declared in unnamed namespace",
diff --git a/gcc/testsuite/g++.dg/modules/export-7.C b/gcc/testsuite/g++.dg/modules/export-7.C
new file mode 100644
index 00000000000..11001390d17
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/export-7.C
@@ -0,0 +1,10 @@ 
+// PR c++/124781
+// { dg-do compile { target c++20 } }
+// { dg-additional-options "-fmodules" }
+// { dg-module-cmi foo }
+
+export module foo;
+export using xx = decltype([] {
+  using yy = int;
+  int abc = 123;
+}());