Fix ICE in get_substring_ranges_for_loc on __FILE__ (PR c++/87721)

PR c++/87721 reports a crash in get_substring_ranges_for_loc introduced
by r265271, my fix for PR 87562.

The new issue occurs when attempting to get a location with a string
literal inside a macro in which the first token is __FILE__ (formed via
concatenation).  Attempting to get the spelling location of __FILE__
fails, leading to NULL for start_ord_map and final_ord_map, and thus
a NULL pointer dereference.

Given that our "on-demand" substring locations approach reparses the
string literals, there isn't a good way to access the locations inside
such string literals: attempting to reparse __FILE__ fails with a
"missing open quote".

This patch applies the easy fix by gracefully rejecting the case where
the spelling locations for the start or finish give us NULL maps.

gcc/ChangeLog:
	PR c++/87721
	* input.c (get_substring_ranges_for_loc): Detect if
	linemap_resolve_location gives us a NULL map, and reject
	this case.

gcc/testsuite/ChangeLog:
	PR c++/87721
	* c-c++-common/substring-location-PR-87721.c: New test.
	* gcc.dg/plugin/diagnostic-test-string-literals-1.c: Add test for
	PR 87721.
	* gcc.dg/plugin/diagnostic_plugin_test_string_literals.c
	(test_string_literals): Fold the index arguments before checking
	for INTEGER_CST.

From-SVN: r265611

gcc/ChangeLog

+2018-10-29  David Malcolm  <dmalcolm@redhat.com>
+
+	PR c++/87721
+	* input.c (get_substring_ranges_for_loc): Detect if
+	linemap_resolve_location gives us a NULL map, and reject
+	this case.
+
 2018-10-29  Iain Buclaw  <ibuclaw@gdcproject.org>
 
 	* config.gcc (xstormy16-*-elf): Set tm_d_file.

gcc/input.c

@@ -1463,6 +1463,8 @@ get_substring_ranges_for_loc (cpp_reader *pfile,
       const line_map_ordinary *final_ord_map;
       linemap_resolve_location (line_table, src_range.m_finish,
 				LRK_SPELLING_LOCATION, &final_ord_map);
+      if (start_ord_map == NULL || final_ord_map == NULL)
+	return "failed to get ordinary maps";
       /* Bulletproofing.  We ought to only have different ordinary maps
 	 for start vs finish due to line-length jumps.  */
       if (start_ord_map != final_ord_map

gcc/testsuite/ChangeLog

 2018-10-29  David Malcolm  <dmalcolm@redhat.com>
 
+	PR c++/87721
+	* c-c++-common/substring-location-PR-87721.c: New test.
+	* gcc.dg/plugin/diagnostic-test-string-literals-1.c: Add test for
+	PR 87721.
+	* gcc.dg/plugin/diagnostic_plugin_test_string_literals.c
+	(test_string_literals): Fold the index arguments before checking
+	for INTEGER_CST.
+
+2018-10-29  David Malcolm  <dmalcolm@redhat.com>
+
 	* c-c++-common/spellcheck-reserved.c: Update expected output for
 	C++ for merger of "did you mean" suggestions into the error
 	message.

gcc/testsuite/c-c++-common/substring-location-PR-87721.c

+# define DBG_ERROR(dbg_logger, format, args...) if (1){\
+  char dbg_buffer[256]; \
+  __builtin_snprintf(dbg_buffer, sizeof(dbg_buffer)-1,\
+  __FILE__":%5d: " format  , __LINE__ , ## args); \
+};
+
+void testPasswordStore1(int argc, char **argv) {
+  const char *pw1="Secret1";
+  char pw[256];
+  DBG_ERROR(0, "Bad password, expected [%s], got [%s].", pw1, pw);
+}

gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-1.c

@@ -319,3 +319,33 @@ pr87652 (const char *stem, int counter)
                                        ^~
      { dg-end-multiline-output "" } */
 }
+
+/* Reproducer for PR 87721.  */
+
+# define OFFSET __builtin_strlen (__FILE__) + __builtin_strlen(":%5d: ")
+
+# define DBG_ERROR(format, caret_idx, start_idx, end_idx)	\
+  do {								\
+    __emit_string_literal_range(__FILE__":%5d: " format,	\
+				OFFSET + caret_idx,		\
+				OFFSET + start_idx,		\
+				OFFSET + end_idx);		\
+  } while (0)
+
+/* { dg-error "unable to read substring location: failed to get ordinary maps" "" { target *-*-* } 329 } */
+/* { dg-begin-multiline-output "" }
+     __emit_string_literal_range(__FILE__":%5d: " format, \
+                                 ^~~~~~~~
+     { dg-end-multiline-output "" { target c } } */
+/* { dg-begin-multiline-output "" }
+     __emit_string_literal_range(__FILE__":%5d: " format, \
+                                 ^
+     { dg-end-multiline-output "" { target c++ } } */
+
+void pr87721 (void) {
+  DBG_ERROR("Bad password, expected [%s], got [%s].", 24, 24, 25); /* { dg-message "in expansion of macro 'DBG_ERROR'" } */
+  /* { dg-begin-multiline-output "" }
+   DBG_ERROR("Bad password, expected [%s], got [%s].", 24, 24, 25);
+   ^~~~~~~~~
+     { dg-end-multiline-output "" } */
+}

gcc/testsuite/gcc.dg/plugin/diagnostic_plugin_test_string_literals.c

@@ -140,7 +140,7 @@ test_string_literals (gimple *stmt)
       return;
     }
 
-  tree t_caret_idx = gimple_call_arg (call, 1);
+  tree t_caret_idx = fold (gimple_call_arg (call, 1));
   if (TREE_CODE (t_caret_idx) != INTEGER_CST)
     {
       error_at (call->location, "integer constant required for arg 2");
@@ -148,7 +148,7 @@ test_string_literals (gimple *stmt)
     }
   int caret_idx = TREE_INT_CST_LOW (t_caret_idx);
 
-  tree t_start_idx = gimple_call_arg (call, 2);
+  tree t_start_idx = fold (gimple_call_arg (call, 2));
   if (TREE_CODE (t_start_idx) != INTEGER_CST)
     {
       error_at (call->location, "integer constant required for arg 3");
@@ -156,7 +156,7 @@ test_string_literals (gimple *stmt)
     }
   int start_idx = TREE_INT_CST_LOW (t_start_idx);
 
-  tree t_end_idx = gimple_call_arg (call, 3);
+  tree t_end_idx = fold (gimple_call_arg (call, 3));
   if (TREE_CODE (t_end_idx) != INTEGER_CST)
     {
       error_at (call->location, "integer constant required for arg 4");