c++: Fix ICE-after-error on partial spec [92068]

Here the template arguments for the partial specialization are valid
arguments for the template, but not for a partial specialization, because
'd' can never be deduced to anything other than an empty pack.

gcc/cp/ChangeLog
2020-03-14  Jason Merrill  <jason@redhat.com>

	PR c++/92068
	* pt.c (process_partial_specialization): Error rather than crash on
	extra pack expansion.

diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index bb7f590ea0b71c4756a46654786ffc18df075617..c9375234c41d46fed62f37f6b246782b492ca57a 100644 (file)
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2020-03-14  Jason Merrill  <jason@redhat.com>
+
+       PR c++/92068
+       * pt.c (process_partial_specialization): Error rather than crash on
+       extra pack expansion.
+
 2020-03-14  Jason Merrill  <jason@redhat.com>
 
        PR c++/92909

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index bd2f9be82eae7da675f7c0c4ac45984a6e927780..48ac48615a0a2327cce8eb3c9baa23da85bd40da 100644 (file)
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -5038,6 +5038,14 @@ process_partial_specialization (tree decl)
       return decl;
     }
 
+  else if (nargs > DECL_NTPARMS (maintmpl))
+    {
+      error ("too many arguments for partial specialization %qT", type);
+      inform (DECL_SOURCE_LOCATION (maintmpl), "primary template here");
+      /* Avoid crash below.  */
+      return decl;
+    }
+
   /* If we aren't in a dependent class, we can actually try deduction.  */
   else if (tpd.level == 1
           /* FIXME we should be able to handle a partial specialization of a
@@ -5064,7 +5072,6 @@ process_partial_specialization (tree decl)
 
      Also, we verify that pack expansions only occur at the
      end of the argument list.  */
-  gcc_assert (nargs == DECL_NTPARMS (maintmpl));
   tpd2.parms = 0;
   for (i = 0; i < nargs; ++i)
     {

diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic178.C b/gcc/testsuite/g++.dg/cpp0x/variadic178.C
new file mode 100644 (file)
index 0000000..f0e6595
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic178.C
@@ -0,0 +1,6 @@
+// PR c++/92068
+// { dg-do compile { target c++11 } }
+
+template <typename, typename> struct a;
+template <typename b, typename c, typename... d>
+struct a<b, c, d...> { };      // { dg-error "arguments" }