Patchwork PR c++/54466 - ICE with alias template which type-id is const qualified

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Submitter Dodji Seketeli
Date Oct. 27, 2012, 7:57 a.m.
Message ID <87y5iscppa.fsf@redhat.com>
Download mbox | patch
Permalink /patch/194606/
State New
Headers show

Comments

Dodji Seketeli - Oct. 27, 2012, 7:57 a.m.
Hello,

Consider this short example:

    template<typename T>
      struct X { };

    template<typename T>
      using Y = const X<T>;

    using Z = Y<int>;

G++ crashes in lookup_class_template_1 while trying to build the alias
template instantiation Y<int>.

I think this is indirectly due to the fact that lookup_class_template_1
can now yield a const qualified type like 'const X<T>'.

As a consequence, the code in lookup_template_class_1 that was trying
to access the TYPE_STUB_DECL field of the result of
lookup_template_class_1 should now be adjusted to access the
TYPE_STUB_DECL of the main variant of the resulting type instead;
because qualified types (constructed with build_qualified_type)
have their TYPE_STUB_DECL set to NULL.

Fixed thus and tested on x86_64-unknown-linux-gnu against trunk.

gcc/cp

	PR c++/54466
	* pt.c (lookup_template_class_1): TYPE_STUB_DECL should be
	accessed on the main variant of the type.

gcc/testsuite/

	* g++.dg/cpp0x/alias-decl-25.C: New test file.

In the example of this patch, g++ crashes when trying to build the
alias template Y<int
---
 gcc/cp/pt.c                                |  5 +++--
 gcc/testsuite/g++.dg/cpp0x/alias-decl-25.C | 10 ++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/alias-decl-25.C
Jason Merrill - Nov. 6, 2012, 7:17 p.m.
OK.  You could also use TYPE_MAIN_DECL instead of TYPE_STUB_DECL.

Jason

Patch

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 1ff1c73..d442f01 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -7371,10 +7371,11 @@  lookup_template_class_1 (tree d1, tree arglist, tree in_decl, tree context,
 
       if (CLASS_TYPE_P (template_type))
 	{
+	  tree tt = TYPE_MAIN_VARIANT (template_type);
 	  TREE_PRIVATE (type_decl)
-	    = TREE_PRIVATE (TYPE_STUB_DECL (template_type));
+	    = TREE_PRIVATE (TYPE_STUB_DECL (tt));
 	  TREE_PROTECTED (type_decl)
-	    = TREE_PROTECTED (TYPE_STUB_DECL (template_type));
+	    = TREE_PROTECTED (TYPE_STUB_DECL (tt));
 	  if (CLASSTYPE_VISIBILITY_SPECIFIED (template_type))
 	    {
 	      DECL_VISIBILITY_SPECIFIED (type_decl) = 1;
diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-25.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-25.C
new file mode 100644
index 0000000..dd4cc02
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-25.C
@@ -0,0 +1,10 @@ 
+// Origin: PR c++/54466
+// { dg-do compile { target c++11 } }
+
+template<typename T>
+  struct X { };
+
+template<typename T>
+  using Y = const X<T>;
+
+using Z = Y<int>;