Patchwork C++ PATCH for c++/48736 (crash with default template argument involving pack expansion)

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Submitter Jason Merrill
Date May 10, 2011, 6:29 p.m.
Message ID <4DC983F6.3030204@redhat.com>
Download mbox | patch
Permalink /patch/95109/
State New
Headers show

Comments

Jason Merrill - May 10, 2011, 6:29 p.m.
tsubst_copy_and_build was assuming that substituting into a pack 
expansion would always produce a vector of elements, which is not true 
if the template arguments are still dependent.

Tested x86_64-pc-linux-gnu, applied to trunk.
commit 3bc57a5e66cd7a4e6e9a77900249db0bf193456b
Author: Jason Merrill <jason@redhat.com>
Date:   Mon May 9 17:13:55 2011 -0400

    	PR c++/48736
    	* pt.c (tsubst_copy_and_build): Handle substitution of a pack
    	expansion producing another expansion.

Patch

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index f6392d6..5e24977 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -13250,7 +13250,8 @@  tsubst_copy_and_build (tree t,
                 ce->value = tsubst_pack_expansion (ce->value, args, complain,
                                                   in_decl);
 
-		if (ce->value == error_mark_node)
+		if (ce->value == error_mark_node
+		    || PACK_EXPANSION_P (ce->value))
 		  ;
 		else if (TREE_VEC_LENGTH (ce->value) == 1)
                   /* Just move the argument into place.  */
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic108.C b/gcc/testsuite/g++.dg/cpp0x/variadic108.C
new file mode 100644
index 0000000..3ad5af4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic108.C
@@ -0,0 +1,10 @@ 
+// PR c++/48736
+// { dg-options -std=c++0x }
+
+template<class T>
+T&& create();
+
+template<class T, class... Args,
+ class = decltype(T{create<Args>()...}) // Line X
+>
+char f(int);