c-format.c: suggest the correct format string to use (PR c/64955)

This adds fix-it hints to c-format.c so that it can (sometimes) suggest
the format string the user should have used.

The patch adds selftests for the new code in c-format.c.  These
selftests are thus lang-specific.  This is the first time we've had
lang-specific selftests, and hence the patch also adds a langhook for
running them.  (Note that currently the Makefile only invokes the
selftests for cc1).

gcc/c-family/ChangeLog:
	PR c/64955
	* c-common.h (selftest::c_format_c_tests): New declaration.
	(selftest::run_c_tests): New declaration.
	* c-format.c: Include "selftest.h.
	(format_warning_va): Add param "corrected_substring" and use
	it to add a replacement fix-it hint.
	(format_warning_at_substring): Likewise.
	(format_warning_at_char): Update for new param of
	format_warning_va.
	(argument_parser::check_argument_type): Pass "fki" to
	check_format_types.
	(check_format_types): Add param "fki" and pass it to
	format_type_warning.
	(deref_n_times): New function.
	(get_modifier_for_format_len): New function.
	(selftest::test_get_modifier_for_format_len): New function.
	(get_format_for_type): New function.
	(format_type_warning): Add param "fki" and use it to attempt
	to provide hints for argument types when calling
	format_warning_at_substring.
	(selftest::get_info): New function.
	(selftest::assert_format_for_type_streq): New function.
	(ASSERT_FORMAT_FOR_TYPE_STREQ): New macro.
	(selftest::test_get_format_for_type_printf): New function.
	(selftest::test_get_format_for_type_scanf): New function.
	(selftest::c_format_c_tests): New function.

gcc/c/ChangeLog:
	PR c/64955
	* c-lang.c (LANG_HOOKS_RUN_LANG_SELFTESTS): If CHECKING_P, wire
	this up to selftest::run_c_tests.
	(selftest::run_c_tests): New function.

gcc/ChangeLog:
	PR c/64955
	* langhooks-def.h (LANG_HOOKS_RUN_LANG_SELFTESTS): New default
	do-nothing langhook.
	(LANG_HOOKS_INITIALIZER): Add LANG_HOOKS_RUN_LANG_SELFTESTS.
	* langhooks.h (struct lang_hooks): Add run_lang_selftests.
	* selftest-run-tests.c: Include "tree.h" and "langhooks.h".
	(selftest::run_tests): Call lang_hooks.run_lang_selftests.

gcc/testsuite/ChangeLog:
	PR c/64955
	* gcc.dg/format/diagnostic-ranges.c: Add fix-it hints to expected
	output.

From-SVN: r239260

11 files changed, 371 insertions, 20 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 34cf61e..dd264b3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,15 @@
 2016-08-08  David Malcolm  <dmalcolm@redhat.com>
 
+	PR c/64955
+	* langhooks-def.h (LANG_HOOKS_RUN_LANG_SELFTESTS): New default
+	do-nothing langhook.
+	(LANG_HOOKS_INITIALIZER): Add LANG_HOOKS_RUN_LANG_SELFTESTS.
+	* langhooks.h (struct lang_hooks): Add run_lang_selftests.
+	* selftest-run-tests.c: Include "tree.h" and "langhooks.h".
+	(selftest::run_tests): Call lang_hooks.run_lang_selftests.
+
+2016-08-08  David Malcolm  <dmalcolm@redhat.com>
+
 	PR bootstrap/72844
 	* input.c: Ensure that HAVE_ICONV is defined.
 
diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index f03a078..5b264e9 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,5 +1,34 @@
 2016-08-08  David Malcolm  <dmalcolm@redhat.com>
 
+	PR c/64955
+	* c-common.h (selftest::c_format_c_tests): New declaration.
+	(selftest::run_c_tests): New declaration.
+	* c-format.c: Include "selftest.h.
+	(format_warning_va): Add param "corrected_substring" and use
+	it to add a replacement fix-it hint.
+	(format_warning_at_substring): Likewise.
+	(format_warning_at_char): Update for new param of
+	format_warning_va.
+	(argument_parser::check_argument_type): Pass "fki" to
+	check_format_types.
+	(check_format_types): Add param "fki" and pass it to
+	format_type_warning.
+	(deref_n_times): New function.
+	(get_modifier_for_format_len): New function.
+	(selftest::test_get_modifier_for_format_len): New function.
+	(get_format_for_type): New function.
+	(format_type_warning): Add param "fki" and use it to attempt
+	to provide hints for argument types when calling
+	format_warning_at_substring.
+	(selftest::get_info): New function.
+	(selftest::assert_format_for_type_streq): New function.
+	(ASSERT_FORMAT_FOR_TYPE_STREQ): New macro.
+	(selftest::test_get_format_for_type_printf): New function.
+	(selftest::test_get_format_for_type_scanf): New function.
+	(selftest::c_format_c_tests): New function.
+
+2016-08-08  David Malcolm  <dmalcolm@redhat.com>
+
 	PR c/52952
 	* c-format.c: Include "diagnostic.h".
 	(location_column_from_byte_offset): Delete.
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 7b5da57..61f9ced 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1533,4 +1533,11 @@ extern bool valid_array_size_p (location_t, tree, tree);
 extern bool cilk_ignorable_spawn_rhs_op (tree);
 extern bool cilk_recognize_spawn (tree, tree *);
 
+#if CHECKING_P
+namespace selftest {
+  extern void c_format_c_tests (void);
+  extern void run_c_tests (void);
+} // namespace selftest
+#endif /* #if CHECKING_P */
+
 #endif /* ! GCC_C_COMMON_H */
diff --git a/gcc/c-family/c-format.c b/gcc/c-family/c-format.c
index eff2ab4..951ffd0 100644
--- a/gcc/c-family/c-format.c
+++ b/gcc/c-family/c-format.c
@@ -30,6 +30,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "langhooks.h"
 #include "c-format.h"
 #include "diagnostic.h"
+#include "selftest.h"
 
 /* Handle attributes associated with format checking.  */
 
@@ -126,11 +127,21 @@ static int format_flags (int format_num);
      printf(fmt, msg);
             ^~~  ~~~
 
+   If CORRECTED_SUBSTRING is non-NULL, use it for cases 1 and 2 to provide
+   a fix-it hint, suggesting that it should replace the text within the
+   substring range.  For example:
+
+     test.c:90:10: warning: problem with '%i' here [-Wformat=]
+     printf ("hello %i", msg);
+                    ~^
+                    %s
+
    Return true if a warning was emitted, false otherwise.  */
 
-ATTRIBUTE_GCC_DIAG (4,0)
+ATTRIBUTE_GCC_DIAG (5,0)
 static bool
 format_warning_va (const substring_loc &fmt_loc, source_range *param_range,
+		   const char *corrected_substring,
 		   int opt, const char *gmsgid, va_list *ap)
 {
   bool substring_within_range = false;
@@ -174,6 +185,9 @@ format_warning_va (const substring_loc &fmt_loc, source_range *param_range,
       richloc.add_range (param_loc, false);
     }
 
+  if (!err && corrected_substring && substring_within_range)
+    richloc.add_fixit_replace (fmt_substring_range, corrected_substring);
+
   diagnostic_info diagnostic;
   diagnostic_set_info (&diagnostic, gmsgid, ap, &richloc, DK_WARNING);
   diagnostic.option_index = opt;
@@ -182,22 +196,31 @@ format_warning_va (const substring_loc &fmt_loc, source_range *param_range,
   if (!err && substring_loc && !substring_within_range)
     /* Case 2.  */
     if (warned)
-      inform (substring_loc, "format string is defined here");
+      {
+	rich_location substring_richloc (line_table, substring_loc);
+	if (corrected_substring)
+	  substring_richloc.add_fixit_replace (fmt_substring_range,
+					       corrected_substring);
+	inform_at_rich_loc (&substring_richloc,
+			    "format string is defined here");
+      }
 
   return warned;
 }
 
 /* Variadic call to format_warning_va.  */
 
-ATTRIBUTE_GCC_DIAG (4,0)
+ATTRIBUTE_GCC_DIAG (5,0)
 static bool
 format_warning_at_substring (const substring_loc &fmt_loc,
 			     source_range *param_range,
+			     const char *corrected_substring,
 			     int opt, const char *gmsgid, ...)
 {
   va_list ap;
   va_start (ap, gmsgid);
-  bool warned = format_warning_va (fmt_loc, param_range, opt, gmsgid, &ap);
+  bool warned = format_warning_va (fmt_loc, param_range, corrected_substring,
+				   opt, gmsgid, &ap);
   va_end (ap);
 
   return warned;
@@ -225,7 +248,7 @@ format_warning_at_char (location_t fmt_string_loc, tree format_string_cst,
   char_idx -= 1;
 
   substring_loc fmt_loc (fmt_string_loc, string_type, char_idx, char_idx);
-  bool warned = format_warning_va (fmt_loc, NULL, opt, gmsgid, &ap);
+  bool warned = format_warning_va (fmt_loc, NULL, NULL, opt, gmsgid, &ap);
   va_end (ap);
 
   return warned;
@@ -1126,11 +1149,13 @@ static const format_flag_spec *get_flag_spec (const format_flag_spec *,
 					      int, const char *);
 
 static void check_format_types (const substring_loc &fmt_loc,
-				format_wanted_type *);
+				format_wanted_type *,
+				const format_kind_info *fki);
 static void format_type_warning (const substring_loc &fmt_loc,
 				 source_range *param_range,
 				 format_wanted_type *, tree,
-				 tree);
+				 tree,
+				 const format_kind_info *fki);
 
 /* Decode a format type from a string, returning the type, or
    format_type_error if not valid, in which case the caller should print an
@@ -2786,7 +2811,7 @@ check_argument_type (const format_char_info *fci,
       ptrdiff_t offset_to_format_end = (format_chars - 1) - orig_format_chars;
       substring_loc fmt_loc (fmt_param_loc, TREE_TYPE (format_string_cst),
 			     offset_to_format_start, offset_to_format_end);
-      check_format_types (fmt_loc, first_wanted_type);
+      check_format_types (fmt_loc, first_wanted_type, fki);
     }
 
   return true;
@@ -2946,7 +2971,7 @@ check_format_info_main (format_check_results *res,
    location of the format conversion.  */
 static void
 check_format_types (const substring_loc &fmt_loc,
-		    format_wanted_type *types)
+		    format_wanted_type *types, const format_kind_info *fki)
 {
   for (; types != 0; types = types->next)
     {
@@ -2973,7 +2998,7 @@ check_format_types (const substring_loc &fmt_loc,
       cur_param = types->param;
       if (!cur_param)
         {
-          format_type_warning (fmt_loc, NULL, types, wanted_type, NULL);
+	  format_type_warning (fmt_loc, NULL, types, wanted_type, NULL, fki);
           continue;
         }
 
@@ -3058,7 +3083,7 @@ check_format_types (const substring_loc &fmt_loc,
 	  else
 	    {
 	      format_type_warning (fmt_loc, param_range_ptr,
-				   types, wanted_type, orig_cur_type);
+				   types, wanted_type, orig_cur_type, fki);
 	      break;
 	    }
 	}
@@ -3127,10 +3152,115 @@ check_format_types (const substring_loc &fmt_loc,
 	continue;
       /* Now we have a type mismatch.  */
       format_type_warning (fmt_loc, param_range_ptr, types,
-			   wanted_type, orig_cur_type);
+			   wanted_type, orig_cur_type, fki);
+    }
+}
+
+/* Given type TYPE, attempt to dereference the type N times
+   (e.g. from ("int ***", 2) to "int *")
+
+   Return the derefenced type, with any qualifiers
+   such as "const" stripped from the result, or
+   NULL if unsuccessful (e.g. TYPE is not a pointer type).  */
+
+static tree
+deref_n_times (tree type, int n)
+{
+  gcc_assert (type);
+
+  for (int i = n; i > 0; i--)
+    {
+      if (TREE_CODE (type) != POINTER_TYPE)
+	return NULL_TREE;
+      type = TREE_TYPE (type);
+    }
+  /* Strip off any "const" etc.  */
+  return build_qualified_type (type, 0);
+}
+
+/* Lookup the format code for FORMAT_LEN within FLI,
+   returning the string code for expressing it, or NULL
+   if it is not found.  */
+
+static const char *
+get_modifier_for_format_len (const format_length_info *fli,
+			     enum format_lengths format_len)
+{
+  for (; fli->name; fli++)
+    {
+      if (fli->index == format_len)
+	return fli->name;
+      if (fli->double_index == format_len)
+	return fli->double_name;
     }
+  return NULL;
+}
+
+#if CHECKING_P
+
+namespace selftest {
+
+static void
+test_get_modifier_for_format_len ()
+{
+  ASSERT_STREQ ("h",
+		get_modifier_for_format_len (printf_length_specs, FMT_LEN_h));
+  ASSERT_STREQ ("hh",
+		get_modifier_for_format_len (printf_length_specs, FMT_LEN_hh));
+  ASSERT_STREQ ("L",
+		get_modifier_for_format_len (printf_length_specs, FMT_LEN_L));
+  ASSERT_EQ (NULL,
+	     get_modifier_for_format_len (printf_length_specs, FMT_LEN_none));
 }
 
+} // namespace selftest
+
+#endif /* CHECKING_P */
+
+/* Generate a string containing the format string that should be
+   used to format arguments of type ARG_TYPE within FKI (effectively
+   the inverse of the checking code).
+
+   If successful, returns a non-NULL string which should be freed
+   by the called.
+   Otherwise, returns NULL.  */
+
+static char *
+get_format_for_type (const format_kind_info *fki, tree arg_type)
+{
+  gcc_assert (arg_type);
+
+  const format_char_info *spec;
+  for (spec = &fki->conversion_specs[0];
+       spec->format_chars;
+       spec++)
+    {
+      tree effective_arg_type = deref_n_times (arg_type,
+					       spec->pointer_count);
+      if (!effective_arg_type)
+	continue;
+      for (int i = 0; i < FMT_LEN_MAX; i++)
+	{
+	  const format_type_detail *ftd = &spec->types[i];
+	  if (!ftd->type)
+	    continue;
+	  if (TYPE_CANONICAL (*ftd->type)
+	      == TYPE_CANONICAL (effective_arg_type))
+	    {
+	      const char *len_modifier
+		= get_modifier_for_format_len (fki->length_char_specs,
+					       (enum format_lengths)i);
+	      if (!len_modifier)
+		len_modifier = "";
+
+	      return xasprintf ("%%%s%c",
+				len_modifier,
+				spec->format_chars[0]);
+	    }
+	}
+   }
+  return NULL;
+}
 
 /* Give a warning at FMT_LOC about a format argument of different type
    from that expected.  If non-NULL, PARAM_RANGE is the source range of the
@@ -3144,9 +3274,10 @@ static void
 format_type_warning (const substring_loc &fmt_loc,
 		     source_range *param_range,
 		     format_wanted_type *type,
-		     tree wanted_type, tree arg_type)
+		     tree wanted_type, tree arg_type,
+		     const format_kind_info *fki)
 {
-  int kind = type->kind;
+  enum format_specifier_kind kind = type->kind;
   const char *wanted_type_name = type->wanted_type_name;
   const char *format_start = type->format_start;
   int format_length = type->format_length;
@@ -3185,12 +3316,18 @@ format_type_warning (const substring_loc &fmt_loc,
       p[pointer_count + 1] = 0;
     }
 
+  /* Attempt to provide hints for argument types, but not for field widths
+     and precisions.  */
+  char *format_for_type = NULL;
+  if (arg_type && kind == CF_KIND_FORMAT)
+    format_for_type = get_format_for_type (fki, arg_type);
+
   if (wanted_type_name)
     {
       if (arg_type)
 	format_warning_at_substring
 	  (fmt_loc, param_range,
-	   OPT_Wformat_,
+	   format_for_type, OPT_Wformat_,
 	   "%s %<%s%.*s%> expects argument of type %<%s%s%>, "
 	   "but argument %d has type %qT",
 	   gettext (kind_descriptions[kind]),
@@ -3200,7 +3337,7 @@ format_type_warning (const substring_loc &fmt_loc,
       else
 	format_warning_at_substring
 	  (fmt_loc, param_range,
-	   OPT_Wformat_,
+	   format_for_type, OPT_Wformat_,
 	   "%s %<%s%.*s%> expects a matching %<%s%s%> argument",
 	   gettext (kind_descriptions[kind]),
 	   (kind == CF_KIND_FORMAT ? "%" : ""),
@@ -3211,7 +3348,7 @@ format_type_warning (const substring_loc &fmt_loc,
       if (arg_type)
 	format_warning_at_substring
 	  (fmt_loc, param_range,
-	   OPT_Wformat_,
+	   format_for_type, OPT_Wformat_,
 	   "%s %<%s%.*s%> expects argument of type %<%T%s%>, "
 	   "but argument %d has type %qT",
 	   gettext (kind_descriptions[kind]),
@@ -3221,12 +3358,14 @@ format_type_warning (const substring_loc &fmt_loc,
       else
 	format_warning_at_substring
 	  (fmt_loc, param_range,
-	   OPT_Wformat_,
+	   format_for_type, OPT_Wformat_,
 	   "%s %<%s%.*s%> expects a matching %<%T%s%> argument",
 	   gettext (kind_descriptions[kind]),
 	   (kind == CF_KIND_FORMAT ? "%" : ""),
 	   format_length, format_start, wanted_type, p);
     }
+
+  free (format_for_type);
 }
 
 
@@ -3747,3 +3886,96 @@ handle_format_attribute (tree *node, tree ARG_UNUSED (name), tree args,
 
   return NULL_TREE;
 }
+
+#if CHECKING_P
+
+namespace selftest {
+
+/* Selftests of location handling.  */
+
+/* Get the format_kind_info with the given name.  */
+
+static const format_kind_info *
+get_info (const char *name)
+{
+  int idx = decode_format_type (name);
+  const format_kind_info *fki = &format_types[idx];
+  ASSERT_STREQ (fki->name, name);
+  return fki;
+}
+
+/* Verify that get_format_for_type (FKI, TYPE) is EXPECTED_FORMAT.  */
+
+static void
+assert_format_for_type_streq (const location &loc, const format_kind_info *fki,
+			      const char *expected_format, tree type)
+{
+  gcc_assert (fki);
+  gcc_assert (expected_format);
+  gcc_assert (type);
+
+  char *actual_format = get_format_for_type (fki, type);
+  ASSERT_STREQ_AT (loc, expected_format, actual_format);
+  free (actual_format);
+}
+
+/* Selftests for get_format_for_type.  */
+
+#define ASSERT_FORMAT_FOR_TYPE_STREQ(EXPECTED_FORMAT, TYPE) \
+  assert_format_for_type_streq (SELFTEST_LOCATION, (fki), (EXPECTED_FORMAT), (TYPE))
+
+/* Selftest for get_format_for_type for "printf"-style functions.  */
+
+static void
+test_get_format_for_type_printf ()
+{
+  const format_kind_info *fki = get_info ("gnu_printf");
+  ASSERT_NE (fki, NULL);
+
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%f", double_type_node);
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%Lf", long_double_type_node);
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%d", integer_type_node);
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%o", unsigned_type_node);
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%ld", long_integer_type_node);
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%lo", long_unsigned_type_node);
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%lld", long_long_integer_type_node);
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%llo", long_long_unsigned_type_node);
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%s", build_pointer_type (char_type_node));
+}
+
+/* Selftest for get_format_for_type for "scanf"-style functions.  */
+
+static void
+test_get_format_for_type_scanf ()
+{
+  const format_kind_info *fki = get_info ("gnu_scanf");
+  ASSERT_NE (fki, NULL);
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%d", build_pointer_type (integer_type_node));
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%u", build_pointer_type (unsigned_type_node));
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%ld",
+				build_pointer_type (long_integer_type_node));
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%lu",
+				build_pointer_type (long_unsigned_type_node));
+  ASSERT_FORMAT_FOR_TYPE_STREQ
+    ("%lld", build_pointer_type (long_long_integer_type_node));
+  ASSERT_FORMAT_FOR_TYPE_STREQ
+    ("%llu", build_pointer_type (long_long_unsigned_type_node));
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%e", build_pointer_type (float_type_node));
+  ASSERT_FORMAT_FOR_TYPE_STREQ ("%le", build_pointer_type (double_type_node));
+}
+
+#undef ASSERT_FORMAT_FOR_TYPE_STREQ
+
+/* Run all of the selftests within this file.  */
+
+void
+c_format_c_tests ()
+{
+  test_get_modifier_for_format_len ();
+  test_get_format_for_type_printf ();
+  test_get_format_for_type_scanf ();
+}
+
+} // namespace selftest
+
+#endif /* CHECKING_P */
diff --git a/gcc/c/ChangeLog b/gcc/c/ChangeLog
index ecae4f1..3161dcb 100644
--- a/gcc/c/ChangeLog
+++ b/gcc/c/ChangeLog
@@ -1,3 +1,10 @@
+2016-08-08  David Malcolm  <dmalcolm@redhat.com>
+
+	PR c/64955
+	* c-lang.c (LANG_HOOKS_RUN_LANG_SELFTESTS): If CHECKING_P, wire
+	this up to selftest::run_c_tests.
+	(selftest::run_c_tests): New function.
+
 2016-08-04  Thomas Schwinge  <thomas@codesourcery.com>
 
 	* c-parser.c (struct oacc_routine_data): Add error_seen and
diff --git a/gcc/c/c-lang.c b/gcc/c/c-lang.c
index 89954b7..b26be6a 100644
--- a/gcc/c/c-lang.c
+++ b/gcc/c/c-lang.c
@@ -38,7 +38,29 @@ enum c_language_kind c_language = clk_c;
 #undef LANG_HOOKS_INIT_TS
 #define LANG_HOOKS_INIT_TS c_common_init_ts
 
+#if CHECKING_P
+#undef LANG_HOOKS_RUN_LANG_SELFTESTS
+#define LANG_HOOKS_RUN_LANG_SELFTESTS selftest::run_c_tests
+#endif /* #if CHECKING_P */
+
 /* Each front end provides its own lang hook initializer.  */
 struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
 
+#if CHECKING_P
+
+namespace selftest {
+
+/* Implementation of LANG_HOOKS_RUN_LANG_SELFTESTS for the C frontend.  */
+
+void
+run_c_tests (void)
+{
+  c_format_c_tests ();
+}
+
+} // namespace selftest
+
+#endif /* #if CHECKING_P */
+
+
 #include "gtype-c.h"
diff --git a/gcc/langhooks-def.h b/gcc/langhooks-def.h
index 034b3b7..c17f998 100644
--- a/gcc/langhooks-def.h
+++ b/gcc/langhooks-def.h
@@ -120,6 +120,7 @@ extern bool lhd_omp_mappable_type (tree);
 #define LANG_HOOKS_BLOCK_MAY_FALLTHRU	hook_bool_const_tree_true
 #define LANG_HOOKS_EH_USE_CXA_END_CLEANUP	false
 #define LANG_HOOKS_DEEP_UNSHARING	false
+#define LANG_HOOKS_RUN_LANG_SELFTESTS   lhd_do_nothing
 
 /* Attribute hooks.  */
 #define LANG_HOOKS_ATTRIBUTE_TABLE		NULL
@@ -319,7 +320,8 @@ extern void lhd_end_section (void);
   LANG_HOOKS_EH_PROTECT_CLEANUP_ACTIONS, \
   LANG_HOOKS_BLOCK_MAY_FALLTHRU, \
   LANG_HOOKS_EH_USE_CXA_END_CLEANUP, \
-  LANG_HOOKS_DEEP_UNSHARING \
+  LANG_HOOKS_DEEP_UNSHARING, \
+  LANG_HOOKS_RUN_LANG_SELFTESTS \
 }
 
 #endif /* GCC_LANG_HOOKS_DEF_H */
diff --git a/gcc/langhooks.h b/gcc/langhooks.h
index 0593424..169a678 100644
--- a/gcc/langhooks.h
+++ b/gcc/langhooks.h
@@ -505,6 +505,9 @@ struct lang_hooks
      gimplification.  */
   bool deep_unsharing;
 
+  /* Run all lang-specific selftests.  */
+  void (*run_lang_selftests) (void);
+
   /* Whenever you add entries here, make sure you adjust langhooks-def.h
      and langhooks.c accordingly.  */
 };
diff --git a/gcc/selftest-run-tests.c b/gcc/selftest-run-tests.c
index 85e101d..9d75a8e 100644
--- a/gcc/selftest-run-tests.c
+++ b/gcc/selftest-run-tests.c
@@ -21,6 +21,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "system.h"
 #include "coretypes.h"
 #include "selftest.h"
+#include "tree.h"
+#include "langhooks.h"
 
 /* This function needed to be split out from selftest.c as it references
    tests from the whole source tree, and so is within
@@ -70,6 +72,9 @@ selftest::run_tests ()
   /* This one relies on most of the above.  */
   function_tests_c_tests ();
 
+  /* Run any lang-specific selftests.  */
+  lang_hooks.run_lang_selftests ();
+
   /* Finished running tests.  */
   long finish_time = get_run_time ();
   long elapsed_time = finish_time - start_time;
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 93f8090..777315e 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+2016-08-08  David Malcolm  <dmalcolm@redhat.com>
+
+	PR c/64955
+	* gcc.dg/format/diagnostic-ranges.c: Add fix-it hints to expected
+	output.
+
 2016-08-08  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
 
 	* gcc.dg/tree-ssa/pr71078-1.c: Add require-effective-target
diff --git a/gcc/testsuite/gcc.dg/format/diagnostic-ranges.c b/gcc/testsuite/gcc.dg/format/diagnostic-ranges.c
index 9e86b52..ff51833 100644
--- a/gcc/testsuite/gcc.dg/format/diagnostic-ranges.c
+++ b/gcc/testsuite/gcc.dg/format/diagnostic-ranges.c
@@ -12,6 +12,25 @@ void test_mismatching_types (const char *msg)
 /* { dg-begin-multiline-output "" }
    printf("hello %i", msg);
                  ~^
+                 %s
+   { dg-end-multiline-output "" } */
+
+
+  printf("hello %s", 42);  /* { dg-warning "format '%s' expects argument of type 'char \\*', but argument 2 has type 'int'" } */
+/* TODO: ideally would also underline "42".  */
+/* { dg-begin-multiline-output "" }
+   printf("hello %s", 42);
+                 ~^
+                 %d
+   { dg-end-multiline-output "" } */
+
+
+  printf("hello %i", (long)0);  /* { dg-warning "format '%i' expects argument of type 'int', but argument 2 has type 'long int' " } */
+/* TODO: ideally would also underline the argument.  */
+/* { dg-begin-multiline-output "" }
+   printf("hello %i", (long)0);
+                 ~^
+                 %ld
    { dg-end-multiline-output "" } */
 }
 
@@ -23,6 +42,7 @@ void test_multiple_arguments (void)
 /* { dg-begin-multiline-output "" }
    printf ("arg0: %i  arg1: %s arg 2: %i",
                             ~^
+                            %d
    { dg-end-multiline-output "" } */
 }
 
@@ -33,6 +53,7 @@ void test_multiple_arguments_2 (int i, int j)
 /* { dg-begin-multiline-output "" }
    printf ("arg0: %i  arg1: %s arg 2: %i",
                             ~^
+                            %d
            100, i + j, 102);
                 ~~~~~         
    { dg-end-multiline-output "" } */
@@ -67,6 +88,7 @@ void test_hex (const char *msg)
 /* { dg-begin-multiline-output "" }
    printf("hello \x25\x69", msg);
                  ~~~~~~~^
+                 %s
    { dg-end-multiline-output "" } */
 }
 
@@ -80,6 +102,7 @@ void test_oct (const char *msg)
 /* { dg-begin-multiline-output "" }
    printf("hello \045\151", msg);
                  ~~~~~~~^
+                 %s
    { dg-end-multiline-output "" } */
 }
 
@@ -98,6 +121,7 @@ void test_multiple (const char *msg)
 /* { dg-begin-multiline-output "" }
    printf("prefix"  "\x25"  "\151"  "suffix",
                      ~~~~~~~~~~~^
+                     %s
   { dg-end-multiline-output "" } */
 }
 
@@ -108,6 +132,7 @@ void test_u8 (const char *msg)
 /* { dg-begin-multiline-output "" }
    printf(u8"hello %i", msg);
                    ~^
+                   %s
    { dg-end-multiline-output "" } */
 }
 
@@ -117,6 +142,7 @@ void test_param (long long_i, long long_j)
 /* { dg-begin-multiline-output "" }
    printf ("foo %s bar", long_i + long_j);
                 ~^       ~~~~~~~~~~~~~~~
+                %ld
    { dg-end-multiline-output "" } */
 }
 
@@ -192,13 +218,14 @@ void test_macro (const char *msg)
 /* { dg-begin-multiline-output "" }
  #define INT_FMT "%i"
                   ~^
+                  %s
    { dg-end-multiline-output "" } */
 }
 
 void test_non_contiguous_strings (void)
 {
   __builtin_printf(" %" "d ", 0.5); /* { dg-warning "20: format .%d. expects argument of type .int., but argument 2 has type .double." } */
-                                    /* { dg-message "26: format string is defined here" "" { target *-*-* } 200 } */
+                                    /* { dg-message "26: format string is defined here" "" { target *-*-* } 227 } */
   /* { dg-begin-multiline-output "" }
    __builtin_printf(" %" "d ", 0.5);
                     ^~~~
@@ -206,6 +233,7 @@ void test_non_contiguous_strings (void)
   /* { dg-begin-multiline-output "" }
    __builtin_printf(" %" "d ", 0.5);
                       ~~~~^
+                      %f
    { dg-end-multiline-output "" } */
 }