[PATCH] c++ modules: static var in inline function [PR104433]

[PATCH] c++ modules: static var in inline function [PR104433]

[Patrick Palka]

The below testcase fails to link with the error

  undefined reference to `f()::y'

ultimately because during stream out for the static VAR_DECL y we
override DECL_EXTERNAL to true, which later during IPA confuses
symbol_table::remove_unreachable_nodes into thinking it's safe
to not emit the symbol.

The streaming code in question already avoids overriding DECL_EXTERNAL
here for DECL_VAR_DECLARED_INLINE_P vars, so it seems natural to do the
same for static vars from an DECL_DECLARED_INLINE_P function scope.

After this patch (and r13-3134-g09df0d8b14dda6), the following now
links:

  import <memory>;
  int main() { std::make_shared<int>(); }

Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?

	PR c++/104433

gcc/cp/ChangeLog:

	* module.cc (trees_out::core_bools): Don't override
	DECL_EXTERNAL to true for static variables from an inline
	function.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/static-2_a.H: New test.
	* g++.dg/modules/static-2_b.C: New test.
---
 gcc/cp/module.cc                          | 3 +++
 gcc/testsuite/g++.dg/modules/static-2_a.H | 8 ++++++++
 gcc/testsuite/g++.dg/modules/static-2_b.C | 9 +++++++++
 3 files changed, 20 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/modules/static-2_a.H
 create mode 100644 gcc/testsuite/g++.dg/modules/static-2_b.C

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 79cbb346ffa..11f68794cd2 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -5397,6 +5397,9 @@ trees_out::core_bools (tree t)
 
 	    case VAR_DECL:
 	      if (TREE_PUBLIC (t)
+		  && !(TREE_STATIC (t)
+		       && DECL_FUNCTION_SCOPE_P (t)
+		       && DECL_DECLARED_INLINE_P (DECL_CONTEXT (t)))
 		  && !DECL_VAR_DECLARED_INLINE_P (t))
 		is_external = true;
 	      break;
diff --git a/gcc/testsuite/g++.dg/modules/static-2_a.H b/gcc/testsuite/g++.dg/modules/static-2_a.H
new file mode 100644
index 00000000000..b4546932a12
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/static-2_a.H
@@ -0,0 +1,8 @@
+// PR c++/104433
+// { dg-additional-options -fmodule-header }
+// { dg-module-cmi {} }
+
+inline int* f() {
+  static int y = 0;
+  return &y;
+}
diff --git a/gcc/testsuite/g++.dg/modules/static-2_b.C b/gcc/testsuite/g++.dg/modules/static-2_b.C
new file mode 100644
index 00000000000..bfd35b0fc15
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/static-2_b.C
@@ -0,0 +1,9 @@
+// PR c++/104433
+// { dg-additional-options -fmodules-ts }
+// { dg-do link }
+
+import "static-2_a.H";
+
+int main() {
+  f();
+}
-- 
2.38.0.rc2

Re: [PATCH] c++ modules: static var in inline function [PR104433]

[Nathan Sidwell]

On 10/6/22 12:19, Patrick Palka wrote:
> The below testcase fails to link with the error
> 
>    undefined reference to `f()::y'
> 
> ultimately because during stream out for the static VAR_DECL y we
> override DECL_EXTERNAL to true, which later during IPA confuses
> symbol_table::remove_unreachable_nodes into thinking it's safe
> to not emit the symbol.
> 
> The streaming code in question already avoids overriding DECL_EXTERNAL
> here for DECL_VAR_DECLARED_INLINE_P vars, so it seems natural to do the
> same for static vars from an DECL_DECLARED_INLINE_P function scope.
> 
> After this patch (and r13-3134-g09df0d8b14dda6), the following now
> links:
> 
>    import <memory>;
>    int main() { std::make_shared<int>(); }
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?

yeah, that's correct -- these are just as inline

> 
> 	PR c++/104433
> 
> gcc/cp/ChangeLog:
> 
> 	* module.cc (trees_out::core_bools): Don't override
> 	DECL_EXTERNAL to true for static variables from an inline
> 	function.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/static-2_a.H: New test.
> 	* g++.dg/modules/static-2_b.C: New test.
> ---
>   gcc/cp/module.cc                          | 3 +++
>   gcc/testsuite/g++.dg/modules/static-2_a.H | 8 ++++++++
>   gcc/testsuite/g++.dg/modules/static-2_b.C | 9 +++++++++
>   3 files changed, 20 insertions(+)
>   create mode 100644 gcc/testsuite/g++.dg/modules/static-2_a.H
>   create mode 100644 gcc/testsuite/g++.dg/modules/static-2_b.C
> 
> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> index 79cbb346ffa..11f68794cd2 100644
> --- a/gcc/cp/module.cc
> +++ b/gcc/cp/module.cc
> @@ -5397,6 +5397,9 @@ trees_out::core_bools (tree t)
>   
>   	    case VAR_DECL:
>   	      if (TREE_PUBLIC (t)
> +		  && !(TREE_STATIC (t)
> +		       && DECL_FUNCTION_SCOPE_P (t)
> +		       && DECL_DECLARED_INLINE_P (DECL_CONTEXT (t)))
>   		  && !DECL_VAR_DECLARED_INLINE_P (t))
>   		is_external = true;
>   	      break;
> diff --git a/gcc/testsuite/g++.dg/modules/static-2_a.H b/gcc/testsuite/g++.dg/modules/static-2_a.H
> new file mode 100644
> index 00000000000..b4546932a12
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/static-2_a.H
> @@ -0,0 +1,8 @@
> +// PR c++/104433
> +// { dg-additional-options -fmodule-header }
> +// { dg-module-cmi {} }
> +
> +inline int* f() {
> +  static int y = 0;
> +  return &y;
> +}
> diff --git a/gcc/testsuite/g++.dg/modules/static-2_b.C b/gcc/testsuite/g++.dg/modules/static-2_b.C
> new file mode 100644
> index 00000000000..bfd35b0fc15
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/static-2_b.C
> @@ -0,0 +1,9 @@
> +// PR c++/104433
> +// { dg-additional-options -fmodules-ts }
> +// { dg-do link }
> +
> +import "static-2_a.H";
> +
> +int main() {
> +  f();
> +}

-- 
Nathan Sidwell