[C PATCH] Another fix for missing diagnostics (PR c/67730)

[Marek Polacek <polacek at redhat dot com>]

This patch continues fixing up this PR, where we were failing to give
diagnostics for attached testcases, because of NULL being defined in
a system header.  Probably the best we can do at this time is just to
use expansion_point_location_if_in_system_header.  That also means we
will warn for "RETURN" macro in the test below -- not sure if that's
wanted, but I currently do not see any way around it.

Bootstrapped/regtested on x86_64-linux, ok for trunk and 5?

2015-10-01  Marek Polacek  <polacek@redhat.com>

	PR c/67730
	* c-typeck.c (convert_for_assignment): Use the expansion point
	location throughout.

	* gcc.dg/pr67730-1.c: New test.
	* gcc.dg/pr67730-2.c: New test.
	* gcc.dg/pr67730.h: New test.

diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index a11ccb2..035f480 100644
--- gcc/c/c-typeck.c
+++ gcc/c/c-typeck.c
@@ -5708,6 +5718,10 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
   tree rname = NULL_TREE;
   bool objc_ok = false;
 
+  /* Use the expansion point location to handle cases such as user's
+     function returning a wrong-type macro defined in a system header.  */
+  location = expansion_point_location_if_in_system_header (location);
+
   if (errtype == ic_argpass)
     {
       tree selector;
diff --git gcc/testsuite/gcc.dg/pr67730-1.c gcc/testsuite/gcc.dg/pr67730-1.c
index e69de29..bb82f6d 100644
--- gcc/testsuite/gcc.dg/pr67730-1.c
+++ gcc/testsuite/gcc.dg/pr67730-1.c
@@ -0,0 +1,16 @@
+/* PR c/67730 */
+/* { dg-do compile } */
+/* { dg-options "-Wc++-compat" } */
+
+#include "pr67730.h"
+
+extern void bar (unsigned char *);
+
+unsigned char *
+f (void *p)
+{
+   unsigned char *uc = ONEP; /* { dg-warning "request for implicit conversion" } */
+   uc = ONEP; /* { dg-warning "request for implicit conversion" } */
+   bar (ONEP); /* { dg-warning "request for implicit conversion" } */
+   return ONEP; /* { dg-warning "request for implicit conversion" } */
+}
diff --git gcc/testsuite/gcc.dg/pr67730-2.c gcc/testsuite/gcc.dg/pr67730-2.c
index e69de29..29d7267 100644
--- gcc/testsuite/gcc.dg/pr67730-2.c
+++ gcc/testsuite/gcc.dg/pr67730-2.c
@@ -0,0 +1,22 @@
+/* PR c/67730 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+#include "pr67730.h"
+
+extern void bar (int);
+
+int
+fn1 (void)
+{
+  int a = NULL; /* { dg-warning "initialization makes integer from pointer" } */
+  a = NULL; /* { dg-warning "assignment makes integer from pointer" } */
+  bar (NULL); /* { dg-warning "passing argument 1" } */
+  return NULL; /* { dg-warning "return makes integer from pointer" } */
+}
+
+int
+fn2 (void)
+{
+  RETURN; /* { dg-warning "return makes integer from pointer" } */
+}
diff --git gcc/testsuite/gcc.dg/pr67730.h gcc/testsuite/gcc.dg/pr67730.h
index e69de29..9a9afc9 100644
--- gcc/testsuite/gcc.dg/pr67730.h
+++ gcc/testsuite/gcc.dg/pr67730.h
@@ -0,0 +1,32 @@
+#pragma GCC system_header
+#define NULL (void *) 0
+#define ONEP (void *) 1
+#define RETURN return NULL
+
+extern void sysbar (unsigned char *);
+
+unsigned char *
+sysfn1 (void *p)
+{
+   unsigned char *uc = ONEP;
+   uc = ONEP;
+   sysbar (ONEP);
+   return ONEP;
+}
+
+extern void sysbar2 (int);
+
+int
+sysfn2 (void)
+{
+  int a = NULL;
+  a = NULL;
+  sysbar2 (NULL);
+  return NULL;
+}
+
+int
+sysfn3 (void)
+{
+  RETURN;
+}

	Marek