[PATCH] Fix check for whether a function is a variadic function

[Patrick Palka]

stdarg_p() apparently returns false for a variadic function that has no
concrete parameters, e.g. "void foo (...);".  This patch fixes this
issue by removing the predicate's seemingly bogus "n != NULL_TREE" test.

(Zero-parameter functions like "void bar (void);" will always have a
void_type_node sentinel in their fntype's argument list.)

OK to commit after testing?

gcc/ChangeLog:
        * tree.c (stdarg_p): Return true for variadic functions with no
        concrete parameters.

gcc/testsuite/ChangeLog:
        * g++.dg/variadic-main.C: New test.
---
 gcc/testsuite/g++.dg/variadic-main.C | 7 +++++++
 gcc/tree.c                           | 2 +-
 2 files changed, 8 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/variadic-main.C

diff --git a/gcc/testsuite/g++.dg/variadic-main.C 
b/gcc/testsuite/g++.dg/variadic-main.C
new file mode 100644
index 0000000..b262bfd
--- /dev/null
+++ b/gcc/testsuite/g++.dg/variadic-main.C
@@ -0,0 +1,7 @@
+/* { dg-options "-Wpedantic" } */
+
+int
+main (...) /* { dg-warning "declared as variadic function" } */
+{
+  return 0;
+}
diff --git a/gcc/tree.c b/gcc/tree.c
index 01860af..d388a1c 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -11518,7 +11518,7 @@ stdarg_p (const_tree fntype)
       n = t;
     }
 
-  return n != NULL_TREE && n != void_type_node;
+  return n != void_type_node;
 }
 
 /* Return true if TYPE has a prototype.  */
-- 
2.4.0.rc2