Re: C++ PATCH for c++/84720, ICE with rvalue ref template parameter

[Jason Merrill]

On Tue, Mar 13, 2018 at 2:54 PM, Jason Merrill  wrote:
> It's unclear to me that it is ever possible to instantiate a template
> taking an rvalue ref parameter, but I guess we might as well handle it
> properly.

...except that such parameters are actually ill-formed, so we should reject.
commit dea7cfdf2f1e7f17befbe3987badba9f74a6b2b9
Author: Jason Merrill 
Date:   Fri Mar 16 14:01:14 2018 -0400

PR c++/84720 - ICE with rvalue ref non-type argument.

* pt.c (invalid_nontype_parm_type_p): Prohibit rvalue reference.
(convert_nontype_argument): Revert earlier change.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 6c96424152e..f7b1b0dd9aa 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -23985,7 +23985,10 @@ invalid_nontype_parm_type_p (tree type, tsubst_flags_t complain)
 {
   if (INTEGRAL_OR_ENUMERATION_TYPE_P (type))
 return false;
-  else if (POINTER_TYPE_P (type))
+  else if (TYPE_PTR_P (type))
+return false;
+  else if (TREE_CODE (type) == REFERENCE_TYPE
+	   && !TYPE_REF_IS_RVALUE (type))
 return false;
   else if (TYPE_PTRMEM_P (type))
 return false;
diff --git a/gcc/testsuite/g++.dg/cpp0x/rv-targ1.C b/gcc/testsuite/g++.dg/cpp0x/rv-targ1.C
index b8e0daba0f7..06516dfa2b9 100644
--- a/gcc/testsuite/g++.dg/cpp0x/rv-targ1.C
+++ b/gcc/testsuite/g++.dg/cpp0x/rv-targ1.C
@@ -1,7 +1,7 @@
 // PR c++/84720
 // { dg-do compile { target c++11 } }
 
-template
+template		// { dg-error "not a valid type" }
 struct a {
   template
   static void b() {

C++ PATCH for c++/84720, ICE with rvalue ref template parameter

[Jason Merrill]

In this testcase, we were crashing because we decided that the int&&
template parameter wasn't a valid argument for itself, which is wrong.
It's unclear to me that it is ever possible to instantiate a template
taking an rvalue ref parameter, but I guess we might as well handle it
properly.

Tested x86_64-pc-linux-gnu, applying to trunk.
commit 78c6cbb0e9fb5796825dc49891c7921e9270c09e
Author: Jason Merrill 
Date:   Tue Mar 13 14:25:00 2018 -0400

PR c++/84720 - ICE with rvalue ref non-type argument.

* pt.c (convert_nontype_argument): Handle rvalue references.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index fdc1c9a7a75..a16aef6bf58 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -6932,11 +6932,18 @@ convert_nontype_argument (tree type, tree expr, tsubst_flags_t complain)
 	  return NULL_TREE;
 	}
 
-  if (!lvalue_p (expr))
+  if (!glvalue_p (expr)
+	  || TYPE_REF_IS_RVALUE (type) != xvalue_p (expr))
 	{
 	  if (complain & tf_error)
-	error ("%qE is not a valid template argument for type %qT "
-		   "because it is not an lvalue", expr, type);
+	{
+	  if (TYPE_REF_IS_RVALUE (type))
+		error ("%qE is not a valid template argument for type %qT "
+		   "because it is not an xvalue", expr, type);
+	  else
+		error ("%qE is not a valid template argument for type %qT "
+		   "because it is not an lvalue", expr, type);
+	}
 	  return NULL_TREE;
 	}
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/rv-targ1.C b/gcc/testsuite/g++.dg/cpp0x/rv-targ1.C
new file mode 100644
index 000..b8e0daba0f7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/rv-targ1.C
@@ -0,0 +1,10 @@
+// PR c++/84720
+// { dg-do compile { target c++11 } }
+
+template
+struct a {
+  template
+  static void b() {
+b();
+  }
+};