[gcc r13-3235] c++ modules: lazy loading from within template [PR99377]

[Patrick Palka <ppalka@gcc.gnu.org>]

https://gcc.gnu.org/g:2ceb4d531a303f3e70d8bb218c8759e6c0688f62

commit r13-3235-g2ceb4d531a303f3e70d8bb218c8759e6c0688f62
Author: Patrick Palka <ppalka@redhat.com>
Date:   Tue Oct 11 15:02:01 2022 -0400

    c++ modules: lazy loading from within template [PR99377]
    
    Here when lazily loading the binding for f due to its first use from the
    template g, processing_template_decl is set which causes the call to
    note_vague_linkage_fn from module_state::read_cluster to have no effect,
    and thus we never push f onto deferred_fns and end up never emitting its
    definition despite needing it.
    
    The behavior of the lazy loading machinery shouldn't be sensitive to
    whether we're inside a template, so to that end this patch makes us
    clear processing_template_decl in the entrypoints lazy_load_binding and
    lazy_load_pendings.
    
            PR c++/99377
    
    gcc/cp/ChangeLog:
    
            * module.cc (lazy_load_binding): Clear processing_template_decl.
            (lazy_load_pendings): Likewise.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/modules/pr99377-2_a.C: New test.
            * g++.dg/modules/pr99377-2_b.C: New test.

Diff:
---
 gcc/cp/module.cc                           | 8 ++++++++
 gcc/testsuite/g++.dg/modules/pr99377-2_a.C | 6 ++++++
 gcc/testsuite/g++.dg/modules/pr99377-2_b.C | 8 ++++++++
 3 files changed, 22 insertions(+)

diff --git a/gcc/cp/module.cc b/gcc/cp/module.cc
index 4d27cebd22c..7ffeefa7c1f 100644
--- a/gcc/cp/module.cc
+++ b/gcc/cp/module.cc
@@ -19083,6 +19083,10 @@ lazy_load_binding (unsigned mod, tree ns, tree id, binding_slot *mslot)
 
   timevar_start (TV_MODULE_IMPORT);
 
+  /* Make sure lazy loading from a template context behaves as if
+     from a non-template context.  */
+  processing_template_decl_sentinel ptds;
+
   /* Stop GC happening, even in outermost loads (because our caller
      could well be building up a lookup set).  */
   function_depth++;
@@ -19131,6 +19135,10 @@ lazy_load_binding (unsigned mod, tree ns, tree id, binding_slot *mslot)
 void
 lazy_load_pendings (tree decl)
 {
+  /* Make sure lazy loading from a template context behaves as if
+     from a non-template context.  */
+  processing_template_decl_sentinel ptds;
+
   tree key_decl;
   pending_key key;
   key.ns = find_pending_key (decl, &key_decl);
diff --git a/gcc/testsuite/g++.dg/modules/pr99377-2_a.C b/gcc/testsuite/g++.dg/modules/pr99377-2_a.C
new file mode 100644
index 00000000000..98d18546d19
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr99377-2_a.C
@@ -0,0 +1,6 @@
+// PR c++/99377
+// { dg-additional-options -fmodules-ts }
+// { dg-module-cmi pr99377_2 }
+export module pr99377_2;
+
+export inline void f() { }
diff --git a/gcc/testsuite/g++.dg/modules/pr99377-2_b.C b/gcc/testsuite/g++.dg/modules/pr99377-2_b.C
new file mode 100644
index 00000000000..1d5d79c788c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/modules/pr99377-2_b.C
@@ -0,0 +1,8 @@
+// PR c++/99377
+// { dg-additional-options -fmodules-ts }
+// { dg-do link }
+import pr99377_2;
+
+template<class> void g() { f(); }
+
+int main() { f(); }