[gcc r11-10055] c++: redeclared hidden friend take 2 [PR105852]

[gcc r11-10055] c++: redeclared hidden friend take 2 [PR105852]

[Jason Merrill]

https://gcc.gnu.org/g:3e39a0a4b71dce674ee30fe71590b0152663b6d8

commit r11-10055-g3e39a0a4b71dce674ee30fe71590b0152663b6d8
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Jun 6 21:49:06 2022 -0400

    c++: redeclared hidden friend take 2 [PR105852]
    
    My previous patch for 105761 avoided copying DECL_TEMPLATE_INFO from a
    friend to a later definition, but in this testcase we have first a
    non-friend declaration and then a definition, and we need to avoid copying
    in that case as well.  But we do still want to set new_template_info to
    avoid GC trouble.
    
    With this change, the modules dump correctly identifies ::foo as a
    non-template function in tpl-friend-2_a.C.
    
    Along the way I noticed that the duplicate_decls handling of
    DECL_UNIQUE_FRIEND_P was backwards for templates, where we don't clobber
    DECL_LANG_SPECIFIC (olddecl) with DECL_LANG_SPECIFIC (newdecl) like we do
    for non-templates.
    
            PR c++/105852
            PR c++/105761
    
    gcc/cp/ChangeLog:
    
            * decl.c (duplicate_decls): Avoid copying template info
            from non-templated friend even if newdecl isn't a definition.
            Correct handling of DECL_UNIQUE_FRIEND_P on templates.
            * pt.c (non_templated_friend_p): New.
            * cp-tree.h (non_templated_friend_p): Declare it.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/modules/tpl-friend-2_a.C: Adjust expected dump.
            * g++.dg/template/friend74.C: New test.

Diff:
---
 gcc/cp/cp-tree.h                              |  1 +
 gcc/cp/decl.c                                 | 16 ++++++---------
 gcc/cp/pt.c                                   | 29 ++++++++++++++++++++++++++-
 gcc/testsuite/g++.dg/modules/tpl-friend-2_a.C |  2 +-
 gcc/testsuite/g++.dg/template/friend74.C      |  8 ++++++++
 5 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index a2d8c1c77b3..fded2527e5e 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7242,6 +7242,7 @@ extern bool push_tinst_level_loc                (tree, location_t);
 extern bool push_tinst_level_loc                (tree, tree, location_t);
 extern void pop_tinst_level                     (void);
 extern struct tinst_level *outermost_tinst_level(void);
+extern bool non_templated_friend_p		(tree);
 extern void init_template_processing		(void);
 extern void print_template_statistics		(void);
 bool template_template_parameter_p		(const_tree);
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index df5361d1184..679ea9c8be7 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -2224,8 +2224,8 @@ duplicate_decls (tree newdecl, tree olddecl, bool hiding, bool was_hidden)
 	      check_no_redeclaration_friend_default_args
 		(old_result, new_result);
 	    }
-	  if (!DECL_UNIQUE_FRIEND_P (old_result))
-	    DECL_UNIQUE_FRIEND_P (new_result) = false;
+	  if (!DECL_UNIQUE_FRIEND_P (new_result))
+	    DECL_UNIQUE_FRIEND_P (old_result) = false;
 
 	  check_default_args (newdecl);
 
@@ -2580,13 +2580,7 @@ duplicate_decls (tree newdecl, tree olddecl, bool hiding, bool was_hidden)
       if (LANG_DECL_HAS_MIN (newdecl))
 	{
 	  DECL_ACCESS (newdecl) = DECL_ACCESS (olddecl);
-	  if (new_defines_function
-	      && DECL_TEMPLATE_INFO (olddecl)
-	      && DECL_UNIQUE_FRIEND_P (DECL_TEMPLATE_RESULT
-				       (DECL_TI_TEMPLATE (olddecl))))
-	    /* Don't copy template info from a non-template friend declaration
-	       in a class template (PR105761).  */;
-	  else if (DECL_TEMPLATE_INFO (newdecl))
+	  if (DECL_TEMPLATE_INFO (newdecl))
 	    {
 	      new_template_info = DECL_TEMPLATE_INFO (newdecl);
 	      if (DECL_TEMPLATE_INSTANTIATION (olddecl)
@@ -2594,8 +2588,10 @@ duplicate_decls (tree newdecl, tree olddecl, bool hiding, bool was_hidden)
 		/* Remember the presence of explicit specialization args.  */
 		TINFO_USED_TEMPLATE_ID (DECL_TEMPLATE_INFO (olddecl))
 		  = TINFO_USED_TEMPLATE_ID (new_template_info);
-	      DECL_TEMPLATE_INFO (newdecl) = DECL_TEMPLATE_INFO (olddecl);
 	    }
+
+	  if (non_templated_friend_p (olddecl))
+	    /* Don't copy tinfo from a non-templated friend (PR105761).  */;
 	  else
 	    DECL_TEMPLATE_INFO (newdecl) = DECL_TEMPLATE_INFO (olddecl);
 	}
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index ec8bf229740..588c46504b4 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -11137,6 +11137,33 @@ outermost_tinst_level (void)
   return level;
 }
 
+/* True iff T is a friend function declaration that is not itself a template
+   and is not defined in a class template.  */
+
+bool
+non_templated_friend_p (tree t)
+{
+  if (t && TREE_CODE (t) == FUNCTION_DECL
+      && DECL_UNIQUE_FRIEND_P (t))
+    {
+      tree ti = DECL_TEMPLATE_INFO (t);
+      if (!ti)
+	return true;
+      /* DECL_FRIEND_CONTEXT is set for a friend defined in class.  */
+      if (DECL_FRIEND_CONTEXT (t))
+	return false;
+      /* Non-templated friends in a class template are still represented with a
+	 TEMPLATE_DECL; check that its primary template is the befriending
+	 class.  Note that DECL_PRIMARY_TEMPLATE is null for
+	 template <class T> friend A<T>::f(); */
+      tree tmpl = TI_TEMPLATE (ti);
+      tree primary = DECL_PRIMARY_TEMPLATE (tmpl);
+      return (primary && primary != tmpl);
+    }
+  else
+    return false;
+}
+
 /* DECL is a friend FUNCTION_DECL or TEMPLATE_DECL.  ARGS is the
    vector of template arguments, as for tsubst.
 
@@ -14079,7 +14106,7 @@ tsubst_function_decl (tree t, tree args, tsubst_flags_t complain,
       /* This special case arises when we have something like this:
 
 	 template <class T> struct S {
-	 friend void f<int>(int, double);
+	   friend void f<int>(int, double);
 	 };
 
 	 Here, the DECL_TI_TEMPLATE for the friend declaration
diff --git a/gcc/testsuite/g++.dg/modules/tpl-friend-2_a.C b/gcc/testsuite/g++.dg/modules/tpl-friend-2_a.C
index 3acacf8ee34..c12857fbf69 100644
--- a/gcc/testsuite/g++.dg/modules/tpl-friend-2_a.C
+++ b/gcc/testsuite/g++.dg/modules/tpl-friend-2_a.C
@@ -16,5 +16,5 @@ template class TPL<int>;  // instantiate
 void foo (int, void *);
 
 // { dg-final { scan-lang-dump {Cluster members:\n  \[0\]=decl definition '::template TPL'\n(  \[.\]=[^\n]*'\n)*  \[.\]=decl declaration '::template foo'\n(  \[.\]=[^\n]*'\n)*  \[.\]=binding '::TPL'} module } }
-// { dg-final { scan-lang-dump {Cluster members:\n  \[0\]=decl declaration '::foo<int>'\n  \[.\]=binding '::foo'} module } }
+// { dg-final { scan-lang-dump {Cluster members:\n  \[0\]=decl declaration '::foo'\n  \[.\]=binding '::foo'} module } }
 // { dg-final { scan-lang-dump {Cluster members:\n  \[0\]=specialization definition '::TPL<int>'} module } }
diff --git a/gcc/testsuite/g++.dg/template/friend74.C b/gcc/testsuite/g++.dg/template/friend74.C
new file mode 100644
index 00000000000..51708334d81
--- /dev/null
+++ b/gcc/testsuite/g++.dg/template/friend74.C
@@ -0,0 +1,8 @@
+// PR c++/105852
+// { dg-additional-options -w }
+
+template <class> struct Local { friend Local False(int *); };
+Local<int> loc;
+Local<int> False(int *);
+void New() { False; }
+Local<int> False(int *) { return Local<int>(); }