RFA (langhook): PATCH for c++/70029, ICE in verify_type with ref-qualifier

Message ID CADzB+2n_AFdP=2BGpjgSi3t8cqvYw0KFJk0Q+qAzG8CfFhgi5g@mail.gmail.com
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  • RFA (langhook): PATCH for c++/70029, ICE in verify_type with ref-qualifier
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Commit Message

Jason Merrill Sept. 8, 2017, 2:56 p.m.
The issue here is that the C++ front end represents the ref-qualifier
as a variant but includes it in the canonical type, because at the
language level the types are distinct.  Note that this is also true of
language-independent qualifiers like "const", so this doesn't seem
like an unreasonable thing for the front end to do.

But as a result, when build_type_attribute_qual_variant builds a
distinct type copy of the ref-qualified type, it is now its own main
variant, while the canonical type is still a variant of another type,
and verify_type doesn't like that.

This patch introduces a langhook to mimic for language-dependent
qualifiers the b_t_a_q_v behavior for cv-qualifiers, i.e. strip them
before making the copy and reintroduce them afterward.

Tested x86_64-pc-linux-gnu.  OK for trunk?
commit 50a71bc8cbf3d17f0039f531b96e64f348b83549
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Sep 8 00:09:46 2017 +0200

            PR c++/70029 - ICE with ref-qualifier and -flto
    gcc/
            * langhooks.h (struct lang_hooks_for_types): Add
            copy_lang_qualifiers.
            * attribs.c (build_type_attribute_qual_variant): Use it.
            * langhooks-def.h (LANG_HOOKS_COPY_LANG_QUALIFIERS): Default to
            NULL.
            (LANG_HOOKS_FOR_TYPES_INITIALIZER): Use it.
            * tree.c (verify_type): Re-enable TYPE_CANONICAL main variant check.
    gcc/cp/
            * tree.c (cxx_copy_lang_qualifiers): New.
            * cp-tree.h: Declare it.
            * cp-objcp-common.h: Define LANG_HOOKS_COPY_LANG_QUALIFIERS.

Comments

Richard Biener Sept. 8, 2017, 4:46 p.m. | #1
On September 8, 2017 4:56:18 PM GMT+02:00, Jason Merrill <jason@redhat.com> wrote:
>The issue here is that the C++ front end represents the ref-qualifier
>as a variant but includes it in the canonical type, because at the
>language level the types are distinct.  Note that this is also true of
>language-independent qualifiers like "const", so this doesn't seem
>like an unreasonable thing for the front end to do.
>
>But as a result, when build_type_attribute_qual_variant builds a
>distinct type copy of the ref-qualified type, it is now its own main
>variant, while the canonical type is still a variant of another type,
>and verify_type doesn't like that.
>
>This patch introduces a langhook to mimic for language-dependent
>qualifiers the b_t_a_q_v behavior for cv-qualifiers, i.e. strip them
>before making the copy and reintroduce them afterward.
>
>Tested x86_64-pc-linux-gnu.  OK for trunk?

OK. 

Richard.

Patch

diff --git a/gcc/attribs.c b/gcc/attribs.c
index faa0649..b8f58a7 100644
--- a/gcc/attribs.c
+++ b/gcc/attribs.c
@@ -959,8 +959,9 @@  build_decl_attribute_variant (tree ddecl, tree attribute)
    Record such modified types already made so we don't make duplicates.  */
 
 tree
-build_type_attribute_qual_variant (tree ttype, tree attribute, int quals)
+build_type_attribute_qual_variant (tree otype, tree attribute, int quals)
 {
+  tree ttype = otype;
   if (! attribute_list_equal (TYPE_ATTRIBUTES (ttype), attribute))
     {
       tree ntype;
@@ -983,6 +984,11 @@  build_type_attribute_qual_variant (tree ttype, tree attribute, int quals)
 	}
 
       ttype = build_qualified_type (ttype, TYPE_UNQUALIFIED);
+      if (lang_hooks.types.copy_lang_qualifiers
+	  && otype != TYPE_MAIN_VARIANT (otype))
+	ttype = (lang_hooks.types.copy_lang_qualifiers
+		 (ttype, TYPE_MAIN_VARIANT (otype)));
+
       ntype = build_distinct_type_copy (ttype);
 
       TYPE_ATTRIBUTES (ntype) = attribute;
@@ -1000,6 +1006,9 @@  build_type_attribute_qual_variant (tree ttype, tree attribute, int quals)
 	TYPE_CANONICAL (ntype) = TYPE_CANONICAL (ttype);
 
       ttype = build_qualified_type (ntype, quals);
+      if (lang_hooks.types.copy_lang_qualifiers
+	  && otype != TYPE_MAIN_VARIANT (otype))
+	ttype = lang_hooks.types.copy_lang_qualifiers (ttype, otype);
     }
   else if (TYPE_QUALS (ttype) != quals)
     ttype = build_qualified_type (ttype, quals);
diff --git a/gcc/cp/cp-objcp-common.h b/gcc/cp/cp-objcp-common.h
index 10fcdf3..3e4cc9c 100644
--- a/gcc/cp/cp-objcp-common.h
+++ b/gcc/cp/cp-objcp-common.h
@@ -99,6 +99,8 @@  extern void cp_register_dumps (gcc::dump_manager *);
 #define LANG_HOOKS_BUILTIN_FUNCTION_EXT_SCOPE cxx_builtin_function_ext_scope
 #undef	LANG_HOOKS_TYPE_HASH_EQ
 #define LANG_HOOKS_TYPE_HASH_EQ	cxx_type_hash_eq
+#undef	LANG_HOOKS_COPY_LANG_QUALIFIERS
+#define LANG_HOOKS_COPY_LANG_QUALIFIERS	cxx_copy_lang_qualifiers
 #undef LANG_HOOKS_MISSING_NORETURN_OK_P
 #define LANG_HOOKS_MISSING_NORETURN_OK_P cp_missing_noreturn_ok_p
 #undef LANG_HOOKS_BLOCK_MAY_FALLTHRU
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index a0e31d3..a57de33 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6963,6 +6963,7 @@  extern tree convert_bitfield_to_declared_type   (tree);
 extern tree cp_save_expr			(tree);
 extern bool cast_valid_in_integral_constant_expression_p (tree);
 extern bool cxx_type_hash_eq			(const_tree, const_tree);
+extern tree cxx_copy_lang_qualifiers		(const_tree, const_tree);
 
 extern void cxx_print_statistics		(void);
 extern bool maybe_warn_zero_as_null_pointer_constant (tree, location_t);
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index 12c31fb..f387f38 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -4626,6 +4626,21 @@  cxx_type_hash_eq (const_tree typea, const_tree typeb)
 			    TYPE_RAISES_EXCEPTIONS (typeb), ce_exact);
 }
 
+/* Copy the language-specific type variant modifiers from TYPEB to TYPEA.  For
+   C++, these are the exception-specifier and ref-qualifier.  */
+
+tree
+cxx_copy_lang_qualifiers (const_tree typea, const_tree typeb)
+{
+  tree type = CONST_CAST_TREE (typea);
+  if (TREE_CODE (type) == FUNCTION_TYPE || TREE_CODE (type) == METHOD_TYPE)
+    {
+      type = build_exception_variant (type, TYPE_RAISES_EXCEPTIONS (typeb));
+      type = build_ref_qualified_type (type, type_memfn_rqual (typeb));
+    }
+  return type;
+}
+
 /* Apply FUNC to all language-specific sub-trees of TP in a pre-order
    traversal.  Called from walk_tree.  */
 
diff --git a/gcc/langhooks-def.h b/gcc/langhooks-def.h
index ea2006c..61b081b 100644
--- a/gcc/langhooks-def.h
+++ b/gcc/langhooks-def.h
@@ -186,6 +186,7 @@  extern tree lhd_unit_size_without_reusable_padding (tree);
   lhd_omp_firstprivatize_type_sizes
 #define LANG_HOOKS_OMP_MAPPABLE_TYPE	lhd_omp_mappable_type
 #define LANG_HOOKS_TYPE_HASH_EQ		NULL
+#define LANG_HOOKS_COPY_LANG_QUALIFIERS NULL
 #define LANG_HOOKS_GET_ARRAY_DESCR_INFO	NULL
 #define LANG_HOOKS_GET_SUBRANGE_BOUNDS	NULL
 #define LANG_HOOKS_GET_TYPE_BIAS	NULL
@@ -211,6 +212,7 @@  extern tree lhd_unit_size_without_reusable_padding (tree);
   LANG_HOOKS_OMP_FIRSTPRIVATIZE_TYPE_SIZES, \
   LANG_HOOKS_OMP_MAPPABLE_TYPE, \
   LANG_HOOKS_TYPE_HASH_EQ, \
+  LANG_HOOKS_COPY_LANG_QUALIFIERS, \
   LANG_HOOKS_GET_ARRAY_DESCR_INFO, \
   LANG_HOOKS_GET_SUBRANGE_BOUNDS, \
   LANG_HOOKS_GET_TYPE_BIAS, \
diff --git a/gcc/langhooks.h b/gcc/langhooks.h
index 88f6f71..b0c9829 100644
--- a/gcc/langhooks.h
+++ b/gcc/langhooks.h
@@ -123,6 +123,10 @@  struct lang_hooks_for_types
      FUNCTION_TYPE or METHOD_TYPE.  */
   bool (*type_hash_eq) (const_tree, const_tree);
 
+  /* If non-NULL, return TYPE1 with any language-specific modifiers copied from
+     TYPE2.  */
+  tree (*copy_lang_qualifiers) (const_tree, const_tree);
+
   /* Return TRUE if TYPE uses a hidden descriptor and fills in information
      for the debugger about the array bounds, strides, etc.  */
   bool (*get_array_descr_info) (const_tree, struct array_descr_info *);
diff --git a/gcc/testsuite/g++.dg/lto/pr70029_0.C b/gcc/testsuite/g++.dg/lto/pr70029_0.C
new file mode 100644
index 0000000..9c8c31c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/lto/pr70029_0.C
@@ -0,0 +1,10 @@ 
+// PR c++/70029
+// { dg-lto-do assemble }
+
+struct A
+{
+  A();
+  int foo() && __attribute__ ((__warn_unused_result__)) { return 0; }
+};
+
+A a;
diff --git a/gcc/tree.c b/gcc/tree.c
index 7a70eb7..721330a 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -13220,9 +13220,7 @@  verify_type (const_tree t)
       debug_tree (ct);
       error_found = true;
     }
-  /* FIXME: this is violated by the C++ FE as discussed in PR70029, when
-     FUNCTION_*_QUALIFIED flags are set.  */
-  if (0 && TYPE_MAIN_VARIANT (t) == t && ct && TYPE_MAIN_VARIANT (ct) != ct)
+  if (TYPE_MAIN_VARIANT (t) == t && ct && TYPE_MAIN_VARIANT (ct) != ct)
    {
       error ("TYPE_CANONICAL of main variant is not main variant");
       debug_tree (ct);