[PATCH, c++, PR77427 ] Set TYPE_STRUCTURAL_EQUALITY for sysv_abi va_list

[Tom de Vries <Tom_deVries at mentor dot com>]

Hi,

this patch fixes a c++ ICE, a p1 6/7 regression.


Consider test.C:
...
void bar (__builtin_va_list &);

struct c
{
  operator const __builtin_va_list &();
  operator __builtin_va_list &();
};

void
foo (void) {
  struct c c1;

  bar (c1);
}
...

The compiler ICEs as follows:
...
test.C: In function ‘void foo()’:
test.C:13:10: internal compiler error: canonical types differ for 
identical types __va_list_tag [1] and __va_list_tag [1]
   bar (c1);
          ^
comptypes(tree_node*, tree_node*, int)
	src/gcc/cp/typeck.c:1430
reference_related_p(tree_node*, tree_node*)
	src/gcc/cp/call.c:1415
reference_binding
	src/gcc/cp/call.c:1559
implicit_conversion
	src/gcc/cp/call.c:1805
build_user_type_conversion_1
	src/gcc/cp/call.c:3776
reference_binding
	src/gcc/cp/call.c:1664
implicit_conversion
	src/gcc/cp/call.c:1805
add_function_candidate
	src/gcc/cp/call.c:2141
add_candidates
	src/gcc/cp/call.c:5394
perform_overload_resolution
	src/gcc/cp/call.c:4066
build_new_function_call(tree_node*, vec<tree_node*, va_gc, vl_embed>**,
  bool, int)
	src/gcc/cp/call.c:4143
finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
  bool, int)
	src/gcc/cp/semantics.c:2440
...

The regression is caused by the commit for PR70955, that adds a 
"sysv_abi va_list" attribute to the struct in the va_list type (which is 
an array of one of struct).

The ICE in comptypes happens as follows: we're comparing two versions of 
va_list type (with identical array element type), each with the 
canonical type set to themselves. Since the types are considered 
identical, they're supposed to have identical canonical types, which is 
not the case, and we run into the ICE.

The patch fixes the ICE by setting the canonical type of the va_list 
struct and array to NULL, forcing structural comparison.


This fix causes a regression for test2.C:
...
template <typename T>
int
fn7 (T ap)
{
  return __builtin_va_arg(ap, int);
}

int
fn8 (__builtin_va_list ap)
{
  return fn7<__builtin_va_list> (ap);
}
...

It causes this warning to appear:
...
test2.C: In function ‘int fn8(__va_list_tag*)’:
test2.C:11:36: warning: ignoring attributes applied to ‘__va_list_tag’ 
after definition [-Wattributes]
   return fn7<__builtin_va_list> (ap);
...

The patch removes the warning by considering the attribute on the 
va_list struct type as engrained in apply_identity_attributes.


Bootstrapped and reg-tested on x86_64.

OK for trunk, 6 branch?

Thanks,
- Tom

Set TYPE_STRUCTURAL_EQUALITY for sysv_abi va_list

2016-09-03  Tom de Vries  <tom@codesourcery.com>

	PR c++/77427
	* config/i386/i386.c (ix86_build_builtin_va_list_64): Set
	TYPE_STRUCTURAL_EQUALITY for record and array.

	* tree.c (apply_identity_attributes): Consider attributes ingrained on
	records and unions.

	* g++.dg/pr77427.C: New test.

---
 gcc/config/i386/i386.c         |  6 +++++-
 gcc/cp/tree.c                  |  3 ++-
 gcc/testsuite/g++.dg/pr77427.C | 17 +++++++++++++++++
 3 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 4531647..4e00dee 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -10550,9 +10550,13 @@ ix86_build_builtin_va_list_64 (void)
 
   TYPE_ATTRIBUTES (record) = tree_cons (get_identifier ("sysv_abi va_list"),
 					NULL_TREE, TYPE_ATTRIBUTES (record));
+  SET_TYPE_STRUCTURAL_EQUALITY (record);
 
   /* The correct type is an array type of one element.  */
-  return build_array_type (record, build_index_type (size_zero_node));
+  tree res = build_array_type (record, build_index_type (size_zero_node));
+  SET_TYPE_STRUCTURAL_EQUALITY (res);
+
+  return res;
 }
 
 /* Setup the builtin va_list data type and for 64-bit the additional
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 6d254dd..0259bbf 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -1244,7 +1244,8 @@ apply_identity_attributes (tree result, tree attribs, bool *remove_attributes)
   tree new_attribs = NULL_TREE;
   tree *p = &new_attribs;
 
-  if (OVERLOAD_TYPE_P (result))
+  if (OVERLOAD_TYPE_P (result)
+      || RECORD_OR_UNION_TYPE_P (result))
     {
       /* On classes and enums all attributes are ingrained.  */
       gcc_assert (attribs == TYPE_ATTRIBUTES (result));
diff --git a/gcc/testsuite/g++.dg/pr77427.C b/gcc/testsuite/g++.dg/pr77427.C
new file mode 100644
index 0000000..544946d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/pr77427.C
@@ -0,0 +1,17 @@
+// { dg-do compile }
+
+void bar (__builtin_va_list &);
+
+struct c
+{
+  operator const __builtin_va_list &();
+  operator __builtin_va_list &();
+};
+
+void
+foo (void)
+{
+  struct c c1;
+
+  bar (c1);
+}