c++/modules: Fix ICE when writing nontrivial variable initializers

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

-- >8 --

The attached testcase Patrick found in PR c++/112899 ICEs because it is
attempting to write a variable initializer that is no longer in the
static_aggregates map.

The issue is that, for non-header modules, the loop in
c_parse_final_cleanups prunes the static_aggregates list, which means
that by the time we get to emitting module information those
initialisers have been lost.

However, we don't actually need to write non-trivial initialisers for
non-header modules, because they've already been emitted as part of the
module TU itself.  Instead let's just only write the initializers from
header modules (which skipped writing them in c_parse_final_cleanups).

gcc/cp/ChangeLog:

	* module.cc (trees_out::write_var_def): Only write initializers
	in header modules.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/init-5_a.C: New test.
	* g++.dg/modules/init-5_b.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
---
 gcc/cp/module.cc                        |  3 ++-
 gcc/testsuite/g++.dg/modules/init-5_a.C |  9 +++++++++
 gcc/testsuite/g++.dg/modules/init-5_b.C | 10 ++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/modules/init-5_a.C
 create mode 100644 gcc/testsuite/g++.dg/modules/init-5_b.C

On Wed, 3 Jan 2024, Nathaniel Shead wrote:

> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
> 
> -- >8 --
> 
> The attached testcase Patrick found in PR c++/112899 ICEs because it is
> attempting to write a variable initializer that is no longer in the
> static_aggregates map.
> 
> The issue is that, for non-header modules, the loop in
> c_parse_final_cleanups prunes the static_aggregates list, which means
> that by the time we get to emitting module information those
> initialisers have been lost.
> 
> However, we don't actually need to write non-trivial initialisers for
> non-header modules, because they've already been emitted as part of the
> module TU itself.  Instead let's just only write the initializers from
> header modules (which skipped writing them in c_parse_final_cleanups).

Makes sense to me.  It seems this may also fix PR103994 where we ICE
in the same spot when streaming out an initializer from the global
module fragment.

> 
> gcc/cp/ChangeLog:
> 
> 	* module.cc (trees_out::write_var_def): Only write initializers
> 	in header modules.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/init-5_a.C: New test.
> 	* g++.dg/modules/init-5_b.C: New test.
> 
> Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
> ---
>  gcc/cp/module.cc                        |  3 ++-
>  gcc/testsuite/g++.dg/modules/init-5_a.C |  9 +++++++++
>  gcc/testsuite/g++.dg/modules/init-5_b.C | 10 ++++++++++
>  3 files changed, 21 insertions(+), 1 deletion(-)
>  create mode 100644 gcc/testsuite/g++.dg/modules/init-5_a.C
>  create mode 100644 gcc/testsuite/g++.dg/modules/init-5_b.C
> 
> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> index 14818131a70..82b61a2c2ad 100644
> --- a/gcc/cp/module.cc
> +++ b/gcc/cp/module.cc
> @@ -11707,7 +11707,8 @@ trees_out::write_var_def (tree decl)
>      {
>        tree dyn_init = NULL_TREE;
>  
> -      if (DECL_NONTRIVIALLY_INITIALIZED_P (decl))
> +      /* We only need to write initializers in header modules.  */
> +      if (header_module_p () && DECL_NONTRIVIALLY_INITIALIZED_P (decl))
>  	{
>  	  dyn_init = value_member (decl,
>  				   CP_DECL_THREAD_LOCAL_P (decl)
> diff --git a/gcc/testsuite/g++.dg/modules/init-5_a.C b/gcc/testsuite/g++.dg/modules/init-5_a.C
> new file mode 100644
> index 00000000000..466b120b5a0
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/init-5_a.C
> @@ -0,0 +1,9 @@
> +// { dg-additional-options "-fmodules-ts" }
> +// { dg-module-cmi M }
> +
> +export module M;
> +
> +export struct A {
> +  static int f() { return -1; }
> +  static inline int x = f();
> +};
> diff --git a/gcc/testsuite/g++.dg/modules/init-5_b.C b/gcc/testsuite/g++.dg/modules/init-5_b.C
> new file mode 100644
> index 00000000000..40973cc6936
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/init-5_b.C
> @@ -0,0 +1,10 @@
> +// { dg-module-do run }
> +// { dg-additional-options "-fmodules-ts" }
> +
> +import M;
> +
> +int main() {
> +  const int& x = A::x;
> +  if (x != -1)
> +    __builtin_abort();
> +}
> -- 
> 2.43.0
> 
>

ok

On 1/2/24 17:43, Nathaniel Shead wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?
> 
> -- >8 --
> 
> The attached testcase Patrick found in PR c++/112899 ICEs because it is
> attempting to write a variable initializer that is no longer in the
> static_aggregates map.
> 
> The issue is that, for non-header modules, the loop in
> c_parse_final_cleanups prunes the static_aggregates list, which means
> that by the time we get to emitting module information those
> initialisers have been lost.
> 
> However, we don't actually need to write non-trivial initialisers for
> non-header modules, because they've already been emitted as part of the
> module TU itself.  Instead let's just only write the initializers from
> header modules (which skipped writing them in c_parse_final_cleanups).
> 
> gcc/cp/ChangeLog:
> 
> 	* module.cc (trees_out::write_var_def): Only write initializers
> 	in header modules.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/init-5_a.C: New test.
> 	* g++.dg/modules/init-5_b.C: New test.
> 
> Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
> ---
>   gcc/cp/module.cc                        |  3 ++-
>   gcc/testsuite/g++.dg/modules/init-5_a.C |  9 +++++++++
>   gcc/testsuite/g++.dg/modules/init-5_b.C | 10 ++++++++++
>   3 files changed, 21 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/modules/init-5_a.C
>   create mode 100644 gcc/testsuite/g++.dg/modules/init-5_b.C
> 
> diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
> index 14818131a70..82b61a2c2ad 100644
> --- a/gcc/cp/module.cc
> +++ b/gcc/cp/module.cc
> @@ -11707,7 +11707,8 @@ trees_out::write_var_def (tree decl)
>       {
>         tree dyn_init = NULL_TREE;
>   
> -      if (DECL_NONTRIVIALLY_INITIALIZED_P (decl))
> +      /* We only need to write initializers in header modules.  */
> +      if (header_module_p () && DECL_NONTRIVIALLY_INITIALIZED_P (decl))
>   	{
>   	  dyn_init = value_member (decl,
>   				   CP_DECL_THREAD_LOCAL_P (decl)
> diff --git a/gcc/testsuite/g++.dg/modules/init-5_a.C b/gcc/testsuite/g++.dg/modules/init-5_a.C
> new file mode 100644
> index 00000000000..466b120b5a0
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/init-5_a.C
> @@ -0,0 +1,9 @@
> +// { dg-additional-options "-fmodules-ts" }
> +// { dg-module-cmi M }
> +
> +export module M;
> +
> +export struct A {
> +  static int f() { return -1; }
> +  static inline int x = f();
> +};
> diff --git a/gcc/testsuite/g++.dg/modules/init-5_b.C b/gcc/testsuite/g++.dg/modules/init-5_b.C
> new file mode 100644
> index 00000000000..40973cc6936
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/init-5_b.C
> @@ -0,0 +1,10 @@
> +// { dg-module-do run }
> +// { dg-additional-options "-fmodules-ts" }
> +
> +import M;
> +
> +int main() {
> +  const int& x = A::x;
> +  if (x != -1)
> +    __builtin_abort();
> +}