Re: C++ PATCH for c++/51930 (instantiation hidden despite visibility attribute)

[Jason Merrill <jason at redhat dot com>]

On 03/05/2012 01:05 PM, Jason Merrill wrote:
> While looking at the class variant of this issue, I noticed that some of
> the code in determine_visibility was wrong; template_class_depth only
> considers unbound template parameters, and the number we want is the
> total number of levels. I've also adjusted the diagnostic for misplaced
> class attributes as manu requested.
>
> Tested x86_64-pc-linux-pc, applying to trunk.

...and here's the patch.
commit b3b1728e0f4f9d565b33f7d8c07f64b60d3503fe
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Feb 14 17:36:48 2012 -0800

    	PR c++/51930
    	* decl2.c (determine_visibility): Correct calculation of class
    	args depth.
    	* decl.c (check_tag_decl): Adjust warning.

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index c47f87c..a18b312 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -4216,17 +4216,20 @@ check_tag_decl (cp_decl_specifier_seq *declspecs)
         error ("%<constexpr%> cannot be used for type declarations");
     }
 
-  if (declspecs->attributes)
+  if (declspecs->attributes && warn_attributes)
     {
-      location_t loc = input_location;
+      location_t loc;
       if (!CLASSTYPE_TEMPLATE_INSTANTIATION (declared_type))
-	/* For a non-template class, use the name location; for a template
-	   class (an explicit instantiation), use the current location.  */
-	input_location = location_of (declared_type);
-      warning (0, "attribute ignored in declaration of %q#T", declared_type);
-      warning (0, "attribute for %q#T must follow the %qs keyword",
-	       declared_type, class_key_or_enum_as_string (declared_type));
-      input_location = loc;
+	/* For a non-template class, use the name location.  */
+	loc = location_of (declared_type);
+      else
+	/* For a template class (an explicit instantiation), use the
+	   current location.  */
+	loc = input_location;
+      warning_at (loc, OPT_Wattributes, "attribute ignored in declaration "
+		  "of %q#T", declared_type);
+      inform (loc, "attribute for %q#T must follow the %qs keyword",
+	      declared_type, class_key_or_enum_as_string (declared_type));
     }
 
   return declared_type;
diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
index bdc962a..7eccf67 100644
--- a/gcc/cp/decl2.c
+++ b/gcc/cp/decl2.c
@@ -2181,12 +2181,8 @@ determine_visibility (tree decl)
 		      ? TYPE_ATTRIBUTES (TREE_TYPE (decl))
 		      : DECL_ATTRIBUTES (decl));
       
-      if (args != error_mark_node
-	  /* Template argument visibility outweighs #pragma or namespace
-	     visibility, but not an explicit attribute.  */
-	  && !lookup_attribute ("visibility", attribs))
+      if (args != error_mark_node)
 	{
-	  int depth = TMPL_ARGS_DEPTH (args);
 	  tree pattern = DECL_TEMPLATE_RESULT (TI_TEMPLATE (tinfo));
 
 	  if (!DECL_VISIBILITY_SPECIFIED (decl))
@@ -2202,10 +2198,31 @@ determine_visibility (tree decl)
 		}
 	    }
 
-	  /* FIXME should TMPL_ARGS_DEPTH really return 1 for null input? */
-	  if (args && depth > template_class_depth (class_type))
-	    /* Limit visibility based on its template arguments.  */
-	    constrain_visibility_for_template (decl, args);
+	  if (args
+	      /* Template argument visibility outweighs #pragma or namespace
+		 visibility, but not an explicit attribute.  */
+	      && !lookup_attribute ("visibility", attribs))
+	    {
+	      int depth = TMPL_ARGS_DEPTH (args);
+	      int class_depth = 0;
+	      if (class_type && CLASSTYPE_TEMPLATE_INFO (class_type))
+		class_depth = TMPL_ARGS_DEPTH (CLASSTYPE_TI_ARGS (class_type));
+	      if (DECL_VISIBILITY_SPECIFIED (decl))
+		{
+		  /* A class template member with explicit visibility
+		     overrides the class visibility, so we need to apply
+		     all the levels of template args directly.  */
+		  int i;
+		  for (i = 1; i <= depth; ++i)
+		    {
+		      tree lev = TMPL_ARGS_LEVEL (args, i);
+		      constrain_visibility_for_template (decl, lev);
+		    }
+		}
+	      else if (depth > class_depth)
+		/* Limit visibility based on its template arguments.  */
+		constrain_visibility_for_template (decl, args);
+	    }
 	}
     }
 
diff --git a/gcc/testsuite/g++.dg/ext/visibility/template11.C b/gcc/testsuite/g++.dg/ext/visibility/template11.C
new file mode 100644
index 0000000..fb47fe2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/visibility/template11.C
@@ -0,0 +1,20 @@
+// PR c++/51930
+// { dg-require-visibility "" }
+// { dg-options "-fvisibility=hidden" }
+// { dg-final { scan-not-hidden "_ZN13template_testI4testE8functionEv" } }
+
+struct test { };
+
+template<typename T>
+struct template_test
+{
+  __attribute__((visibility("default")))
+  void function();
+};
+
+template<typename T>
+void template_test<T>::function() { }
+
+template
+struct __attribute__((visibility("default")))
+template_test<test>;