PR preprocessor/53463 - Fix system header detection for built-in macro tokens

The location for a built-in macro token is BUILTIN_LOCATION.  When we
see that location value, we cannot know if that token was used in a
system header or not.  And that can trigger some unwanted warnings on
e.g, the use of __LONG_LONG_MAX__ built-in macro in system headers
when we compile with -pedantic, like in the test case accompanying
this patch.

In that case, I think we ought to step-up to see where the built-in
macro has been expanded, until we see a location that is not for a
built-in macro.  Then we can check if the resulting location is in a
system header or not.

Now that we step up to the location of first non-built-in-macro token,
it appeared that for
testsuite/c-c++-common/dfp/convert-int-saturate.c, G++ then fails to
emit the warning in:

    volatile unsigned int usi;
    int
    main ()
    {
      usi = DEC32_MAX;  /* { dg-warning "overflow in implicit constant conversion" } */
     ...
    }

Because DEC32_MAX is defined in the system header float.h as a
built-in macro:

    #define DEC32_MAX	__DEC32_MAX__

And during the parsing of the assignment expression that should have
led to the warning above, input_location is set to the location for
the DEC32_MAX, which is actually the location for the built-in
__DECL32_MAX_EXP.

A possible fix is to use the location of the "=" operator as the
default location for assignment expressions.  This is what the patch
does.

I had to adjust a couple of tests to arrange for this.

Bootstrapped and tested on x86_64-unknown-linux-gnu against trunk.

libcpp/

	PR preprocessor/53463
	* line-map.c (linemap_location_in_system_header_p): For built-in
	macro tokens, check the first expansion point location for that is
	not for a token coming from a built-in macro.

gcc/cp/

	PR preprocessor/53463
	* parser.c (cp_parser_assignment_expression): Use the location
	for the LHS as the default location for the expression.

gcc/testsuite/

	PR preprocessor/53463
	* g++.dg/cpp/limits.C: New test.
	* g++.dg/parse/error19.C: Adjust.
	* g++.dg/warn/Wconversion-real-integer2.C: Likewise.
	* g++.dg/warn/pr35635.C: Likewise.
	* g++.old-deja/g++.pt/assign1.C: Likewise.

From-SVN: r188203

gcc/ChangeLog

+2012-06-04  Dodji Seketeli  <dodji@redhat.com>
+
+	PR preprocessor/53463
+	* parser.c (cp_parser_assignment_expression): Use the location
+	for the '=' as the default location for the expression.
+
 2012-06-04  Edmar Wienskoski  <edmar@freescale.com>
 
 	PR target/53559

gcc/cp/parser.c

@@ -7481,6 +7481,7 @@ cp_parser_assignment_expression (cp_parser* parser, bool cast_p,
 	  if (assignment_operator != ERROR_MARK)
 	    {
 	      bool non_constant_p;
+	      location_t saved_input_location;
 
 	      /* Parse the right-hand side of the assignment.  */
 	      tree rhs = cp_parser_initializer_clause (parser, &non_constant_p);
@@ -7493,11 +7494,15 @@ cp_parser_assignment_expression (cp_parser* parser, bool cast_p,
 	      if (cp_parser_non_integral_constant_expression (parser,
 							      NIC_ASSIGNMENT))
 		return error_mark_node;
-	      /* Build the assignment expression.  */
+	      /* Build the assignment expression.  Its default
+		 location is the location of the '=' token.  */
+	      saved_input_location = input_location;
+	      input_location = loc;
 	      expr = build_x_modify_expr (loc, expr,
 					  assignment_operator,
 					  rhs,
 					  tf_warning_or_error);
+	      input_location = saved_input_location;
 	    }
 	}
     }

gcc/testsuite/ChangeLog

+2012-06-04  Dodji Seketeli  <dodji@redhat.com>
+
+	PR preprocessor/53463
+	* g++.dg/cpp/limits.C: New test.
+	* g++.dg/parse/error19.C: Adjust.
+	* g++.dg/warn/Wconversion-real-integer2.C: Likewise.
+	* g++.dg/warn/pr35635.C: Likewise.
+	* g++.old-deja/g++.pt/assign1.C: Likewise.
+
 2012-06-04  Edmar Wienskoski  <edmar@freescale.com>
 
 	PR target/53559

gcc/testsuite/g++.dg/cpp/limits.C

+// { dg-options "-pedantic" }
+// { dg-do compile }
+
+#include <limits>
+
+// Compiling this with -pedantic was wrongly triggering this error:
+// libstdc++-v3/include/limits:1269:45: warning : use of C++0x long long integer constant [-Wlong-long]
+//       min() _GLIBCXX_USE_NOEXCEPT { return -__LONG_LONG_MAX__ - 1; }
+//                                             ^
+// libstdc++-v3/include/limits:1272:44: warning : use of C++0x long long integer constant [-Wlong-long]
+//       max() _GLIBCXX_USE_NOEXCEPT { return __LONG_LONG_MAX__; }
+//                                            ^
+// libstdc++-v3/include/limits:1342:44: warning : use of C++0x long long integer constant [-Wlong-long]
+//       max() _GLIBCXX_USE_NOEXCEPT { return __LONG_LONG_MAX__ * 2ULL + 1
+//                                            ^
+
+int
+main ()
+{
+    return 0;
+}

gcc/testsuite/g++.dg/parse/error19.C

@@ -10,6 +10,6 @@ const A& foo();
 
 void bar()
 {
-  foo()=A(0); // { dg-error "12:no match for 'operator='" }
+  foo()=A(0); // { dg-error "8:no match for 'operator='" }
   // { dg-message "candidate" "candidate note" { target *-*-* } 13 }
 }

gcc/testsuite/g++.dg/warn/Wconversion-real-integer2.C

@@ -23,11 +23,11 @@
 //
 // That is more useful.
 
-#define INT_MAX __INT_MAX__ // { dg-warning "conversion to .float. alters .int. constant value" }
+#define INT_MAX __INT_MAX__ 
 
 float  vfloat;
 
 void h (void)
 {
-    vfloat = INT_MAX; // { dg-message "in expansion of macro 'INT_MAX'" }
+    vfloat = INT_MAX; // { dg-warning "conversion to .float. alters .int. constant value" }
 }

gcc/testsuite/g++.dg/warn/pr35635.C

@@ -62,9 +62,9 @@ void func3()
   /* At least one branch of ? does not fit in the destination, thus
      warn.  */
   uchar_x = bar != 0 ? 2.1 : 10; /* { dg-warning "conversion" } */
-  uchar_x = bar != 0 
+  uchar_x = bar != 0  /* { dg-warning "negative integer implicitly converted to unsigned type" } */
     ? (unsigned char) 1024 
-    : -1; /* { dg-warning "negative integer implicitly converted to unsigned type" } */
+    : -1; 
 }
 
 void func4()

gcc/testsuite/g++.old-deja/g++.pt/assign1.C

@@ -2,7 +2,7 @@
 // Origin: Mark Mitchell <mark@codesourcery.com>
 
 template <class T>
-struct S {			// { dg-error "const|operator=" }
+struct S {  // { dg-error "const member\[^\n\r\]*can't use default assignment operator" }
   S();
   T t;
 };

libcpp/ChangeLog

+2012-06-04  Dodji Seketeli  <dodji@redhat.com>
+
+	PR preprocessor/53463
+	* line-map.c (linemap_location_in_system_header_p): For built-in
+	macro tokens, check the first expansion point location that is not
+	for a token coming from a built-in macro.
+
 2012-05-29  Joseph Myers  <joseph@codesourcery.com>
 
 	* directives.c: Fix typos.

libcpp/line-map.c

@@ -755,13 +755,35 @@ linemap_location_in_system_header_p (struct line_maps *set,
 {
   const struct line_map *map = NULL;
 
-  location =
-    linemap_resolve_location (set, location, LRK_SPELLING_LOCATION, &map);
-
   if (location < RESERVED_LOCATION_COUNT)
     return false;
 
-  return LINEMAP_SYSP (map);
+  /* Let's look at where the token for LOCATION comes from.  */
+  while (true)
+    {
+      map = linemap_lookup (set, location);
+      if (map != NULL)
+	{
+	  if (!linemap_macro_expansion_map_p (map))
+	    /* It's a normal token.  */
+	    return LINEMAP_SYSP (map);
+	  else
+	    {
+	      /* It's a token resulting from a macro expansion.  */
+	      source_location loc =
+		linemap_macro_map_loc_unwind_toward_spelling (map, location);
+	      if (loc < RESERVED_LOCATION_COUNT)
+		/* This token might come from a built-in macro.  Let's
+		   look at where that macro got expanded.  */
+		location = linemap_macro_map_loc_to_exp_point (map, location);
+	      else
+		location = loc;
+	    }
+	}
+      else
+	break;
+    }
+  return false;
 }
 
 /* Return TRUE if LOCATION is a source code location of a token coming