--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/c99-const-expr-5.c	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,39 @@
+/* Test null pointer constants: typedefs for void should be OK but not
+   qualified void.  */
+/* Origin: Joseph Myers <joseph@codesourcery.com> */
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1999 -pedantic-errors" } */
+
+typedef void V;
+int *p;
+long *q;
+int j;
+void (*fp)(void);
+
+void
+f (void)
+{
+  /* (V *)0 is a null pointer constant, so the assignment should be
+     diagnosed.  */
+  q = (j ? p : (V *)0); /* { dg-error "assignment to 'long int \\*' from incompatible pointer type 'int \\*'" } */
+  q = (j ? p : (void *)0); /* { dg-error "assignment to 'long int \\*' from incompatible pointer type 'int \\*'" } */
+  /* And this conversion should be valid.  */
+  (void (*)(void))(V *)0;
+  (void (*)(void))(void *)0;
+  /* Pointers to qualified void are not valid null pointer
+     constants.  */
+  fp = (const void *)0; /* { dg-error "ISO C forbids assignment between function pointer and 'void \\*'" } */
+  fp = (void *)0;
+  fp = (V *)0;
+  fp = 0;
+  fp == 0;
+  0 == fp;
+  fp == (void *)0;
+  (void *)0 == fp;
+  fp == (V *)0;
+  (V *)0 == fp;
+  fp == (V *)1; /* { dg-error "ISO C forbids comparison of 'void \\*' with function pointer" } */
+  (V *)1 == fp; /* { dg-error "ISO C forbids comparison of 'void \\*' with function pointer" } */
+  fp == (const void *)0; /* { dg-error "ISO C forbids comparison of 'void \\*' with function pointer" } */
+  (const void *)0 == fp; /* { dg-error "ISO C forbids comparison of 'void \\*' with function pointer" } */
+}