C++ PATCH for c++/7046 (#pragma pack and class templates)

[Jason Merrill <jason at redhat dot com>]

We don't use TYPE_PRECISION for anything in class templates, so we might 
as well use it to remember the value of maximum_field_alignment.

Tested x86_64-pc-linux-gnu, applied to trunk.
commit 79f9e0a74065393ef6a48744ee18d47a567df655
Author: Jason Merrill <jason@redhat.com>
Date:   Thu Nov 5 18:27:37 2009 -0500

    	PR c++/7046
    	* class.c (finish_struct): Store maximum_field_alignment in
    	TYPE_PRECISION.
    	* pt.c (instantiate_class_template): Set maximum_field_alignment.

diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index dc4c6b3..4020144 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -5516,6 +5516,9 @@ finish_struct (tree t, tree attributes)
 	if (DECL_PURE_VIRTUAL_P (x))
 	  VEC_safe_push (tree, gc, CLASSTYPE_PURE_VIRTUALS (t), x);
       complete_vars (t);
+
+      /* Remember current #pragma pack value.  */
+      TYPE_PRECISION (t) = maximum_field_alignment;
     }
   else
     finish_struct_1 (t);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index d4556cd..75180ea 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -7352,6 +7352,7 @@ instantiate_class_template (tree type)
   tree typedecl;
   tree pbinfo;
   tree base_list;
+  unsigned int saved_maximum_field_alignment;
 
   if (type == error_mark_node)
     return error_mark_node;
@@ -7412,6 +7413,9 @@ instantiate_class_template (tree type)
   push_deferring_access_checks (dk_no_deferred);
 
   push_to_top_level ();
+  /* Use #pragma pack from the template context.  */
+  saved_maximum_field_alignment = maximum_field_alignment;
+  maximum_field_alignment = TYPE_PRECISION (pattern);
 
   SET_CLASSTYPE_INTERFACE_UNKNOWN (type);
 
@@ -7827,6 +7831,7 @@ instantiate_class_template (tree type)
   perform_typedefs_access_check (pattern, args);
   perform_deferred_access_checks ();
   pop_nested_class ();
+  maximum_field_alignment = saved_maximum_field_alignment;
   pop_from_top_level ();
   pop_deferring_access_checks ();
   pop_tinst_level ();
diff --git a/gcc/testsuite/g++.dg/abi/pragma-pack1.C b/gcc/testsuite/g++.dg/abi/pragma-pack1.C
new file mode 100644
index 0000000..d90fc20
--- /dev/null
+++ b/gcc/testsuite/g++.dg/abi/pragma-pack1.C
@@ -0,0 +1,37 @@
+// PR c++/7046
+
+extern "C" int printf (const char *, ...);
+
+#pragma pack(4)
+
+template <typename X >
+struct T
+{
+    char      x1;   /* Usually 3 padding bytes are added after x1 member. */
+    int       x2;
+};
+
+template <class T>
+int f()
+{
+  struct A { char i1; int i2; };
+  return sizeof (A);
+}
+
+#pragma pack(1)
+template struct T<int>;   /* T<int> is instantiated here */
+template int f<int>();
+
+#pragma pack(4)
+template struct T<float>; /* T<float> is instantiated here */
+template int f<double>();
+
+int main()
+{
+  printf("sizeof T<int>   = %d\n", sizeof(T<int>));
+  printf("sizeof T<float> = %d\n", sizeof(T<float>));
+  printf("f<int>()        = %d\n", f<int>());
+  printf("f<float>()      = %d\n", f<float>());
+  return (sizeof(T<int>) != sizeof(T<float>)
+	  || f<int>() != f<float>());
+}