Support string locations for C++ in -Wformat (PR c++/56856)

-Wformat in the C++ FE doesn't work as well as it could:
(a) it doesn't report precise locations within the string literal, and
(b) it doesn't underline arguments for those arguments !CAN_HAVE_LOCATION_P,
despite having location wrapper nodes.

For example:

  Wformat-ranges.C:32:10: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'int' [-Wformat=]
  32 |   printf("hello %s", 42);
     |          ^~~~~~~~~~

(a) is due to not wiring up the langhook for extracting substring
    locations.

    This patch uses the one in c-family; it also fixes string literal
    parsing so that it records string concatenations (needed for
    extracting substring locations from concatenated strings).

(b) is due to the call to maybe_constant_value here:
       fargs[j] = maybe_constant_value (argarray[j]);
    within build_over_call.

    The patch fixes this by building a vec of location_t values when
    calling check_function_arguments.
    I attempted to eliminate the maybe_constant_value call here, but
    it's needed by e.g. check_function_sentinel for detecting NULL,
    and that code is in "c-family", so it can't simply call into
    maybe_constant_value (which is in "cp").

With this patch, the output for the above example is improved to:

  Wformat-ranges.C:32:18: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'int' [-Wformat=]
  32 |   printf("hello %s", 42);
     |                 ~^   ~~
     |                  |   |
     |                  |   int
     |                  char*
     |                 %d

gcc/cp/ChangeLog:
	PR c++/56856
	* call.c (build_over_call): Build a vec of locations of the
	arguments before the call to maybe_constant_value, and pass to
	check_function_arguments.
	* cp-lang.c (LANG_HOOKS_GET_SUBSTRING_LOCATION): Define as
	c_get_substring_location.
	* parser.c (cp_parser_string_literal): Capture string
	concatenation locations.

gcc/ChangeLog:
	PR c++/56856
	* input.c (expand_location_to_spelling_point): Add param "aspect"
	and use rather than hardcoding LOCATION_ASPECT_CARET.
	(get_substring_ranges_for_loc): Handle the case of a single token
	within a macro expansion.
	* input.h (expand_location_to_spelling_point): Add "aspect" param,
	defaulting to LOCATION_ASPECT_CARET.

gcc/testsuite/ChangeLog:
	PR c++/56856
	* g++.dg/ext/builtin4.C: Set expected location for warning to the
	correct location within the format string.
	* g++.dg/plugin/plugin.exp (plugin_test_list): Add the plugin and
	files for testing locations within string literal locations from
	the C frontend.
	* g++.dg/warn/Wformat-method.C: New test.
	* g++.dg/warn/Wformat-pr71863.C: New test.
	* g++.dg/warn/Wformat-ranges-c++11.C: New test.
	* g++.dg/warn/Wformat-ranges.C: New test, based on
	gcc.dg/format/diagnostic-ranges.c.
	* gcc.dg/plugin/diagnostic-test-string-literals-1.c
	(test_multitoken_macro): Generalize expected output to work with
	both C and C++.
	* gcc.dg/plugin/diagnostic-test-string-literals-2.c
	(test_stringified_token_1): Likewise.
	(test_stringified_token_3): Likewise.

From-SVN: r264887

gcc/ChangeLog

+2018-10-05  David Malcolm  <dmalcolm@redhat.com>
+
+	PR c++/56856
+	* input.c (expand_location_to_spelling_point): Add param "aspect"
+	and use rather than hardcoding LOCATION_ASPECT_CARET.
+	(get_substring_ranges_for_loc): Handle the case of a single token
+	within a macro expansion.
+	* input.h (expand_location_to_spelling_point): Add "aspect" param,
+	defaulting to LOCATION_ASPECT_CARET.
+
 2018-10-05  Paul Koning  <ni1d@arrl.net>
 
 	* config/pdp11/pdp11.c (TARGET_CXX_GUARD_TYPE): Define.

gcc/cp/ChangeLog

+2018-10-05  David Malcolm  <dmalcolm@redhat.com>
+
+	PR c++/56856
+	* call.c (build_over_call): Build a vec of locations of the
+	arguments before the call to maybe_constant_value, and pass to
+	check_function_arguments.
+	* cp-lang.c (LANG_HOOKS_GET_SUBSTRING_LOCATION): Define as
+	c_get_substring_location.
+	* parser.c (cp_parser_string_literal): Capture string
+	concatenation locations.
+
 2018-10-04  Nathan Sidwell  <nathan@acm.org>
 
 	* lang-specs.h: Use string contatenation, not line splicing.

gcc/cp/call.c

@@ -8188,6 +8188,7 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
     {
       tree *fargs = (!nargs ? argarray
 			    : (tree *) alloca (nargs * sizeof (tree)));
+      auto_vec<location_t> arglocs (nargs);
       for (j = 0; j < nargs; j++)
 	{
 	  /* For -Wformat undo the implicit passing by hidden reference
@@ -8197,10 +8198,11 @@ build_over_call (struct z_candidate *cand, int flags, tsubst_flags_t complain)
 	    fargs[j] = TREE_OPERAND (argarray[j], 0);
 	  else
 	    fargs[j] = maybe_constant_value (argarray[j]);
+	  arglocs.quick_push (EXPR_LOC_OR_LOC (argarray[j], input_location));
 	}
 
       warned_p = check_function_arguments (input_location, fn, TREE_TYPE (fn),
-					   nargs, fargs, NULL);
+					   nargs, fargs, &arglocs);
     }
 
   if (DECL_INHERITED_CTOR (fn))

gcc/cp/cp-lang.c

@@ -83,6 +83,9 @@ static tree cxx_enum_underlying_base_type (const_tree);
 #define LANG_HOOKS_RUN_LANG_SELFTESTS selftest::run_cp_tests
 #endif /* #if CHECKING_P */
 
+#undef LANG_HOOKS_GET_SUBSTRING_LOCATION
+#define LANG_HOOKS_GET_SUBSTRING_LOCATION c_get_substring_location
+
 /* Each front end provides its own lang hook initializer.  */
 struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
 

gcc/cp/parser.c

@@ -4034,6 +4034,7 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
   tree value;
   size_t count;
   struct obstack str_ob;
+  struct obstack loc_ob;
   cpp_string str, istr, *strs;
   cp_token *tok;
   enum cpp_ttype type, curr_type;
@@ -4090,6 +4091,7 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
     {
       location_t last_tok_loc = tok->location;
       gcc_obstack_init (&str_ob);
+      gcc_obstack_init (&loc_ob);
       count = 0;
 
       do
@@ -4135,6 +4137,7 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
 	    }
 
 	  obstack_grow (&str_ob, &str, sizeof (cpp_string));
+	  obstack_grow (&loc_ob, &tok->location, sizeof (location_t));
 
 	  last_tok_loc = tok->location;
 
@@ -4173,6 +4176,12 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
     {
       value = build_string (istr.len, (const char *)istr.text);
       free (CONST_CAST (unsigned char *, istr.text));
+      if (count > 1)
+	{
+	  location_t *locs = (location_t *)obstack_finish (&loc_ob);
+	  gcc_assert (g_string_concat_db);
+	  g_string_concat_db->record_string_concatenation (count, locs);
+	}
 
       switch (type)
 	{
@@ -4209,7 +4218,10 @@ cp_parser_string_literal (cp_parser *parser, bool translate, bool wide_ok,
     value = error_mark_node;
 
   if (count > 1)
-    obstack_free (&str_ob, 0);
+    {
+      obstack_free (&str_ob, 0);
+      obstack_free (&loc_ob, 0);
+    }
 
   return cp_expr (value, loc);
 }

gcc/input.c

@@ -813,10 +813,10 @@ expand_location (source_location loc)
    "<built-in>".  */
 
 expanded_location
-expand_location_to_spelling_point (source_location loc)
+expand_location_to_spelling_point (source_location loc,
+				   enum location_aspect aspect)
 {
-  return expand_location_1 (loc, /*expansion_point_p=*/false,
-			    LOCATION_ASPECT_CARET);
+  return expand_location_1 (loc, /*expansion_point_p=*/false, aspect);
 }
 
 /* The rich_location class within libcpp requires a way to expand
@@ -1397,24 +1397,32 @@ get_substring_ranges_for_loc (cpp_reader *pfile,
       source_range src_range = get_range_from_loc (line_table, strlocs[i]);
 
       if (src_range.m_start >= LINEMAPS_MACRO_LOWEST_LOCATION (line_table))
-	/* If the string is within a macro expansion, we can't get at the
-	   end location.  */
-	return "macro expansion";
-
-      if (src_range.m_start >= LINE_MAP_MAX_LOCATION_WITH_COLS)
-	/* If so, we can't reliably determine where the token started within
-	   its line.  */
-	return "range starts after LINE_MAP_MAX_LOCATION_WITH_COLS";
-
-      if (src_range.m_finish >= LINE_MAP_MAX_LOCATION_WITH_COLS)
-	/* If so, we can't reliably determine where the token finished within
-	   its line.  */
-	return "range ends after LINE_MAP_MAX_LOCATION_WITH_COLS";
+	{
+	  /* If the string token was within a macro expansion, then we can
+	     cope with it for the simple case where we have a single token.
+	     Otherwise, bail out.  */
+	  if (src_range.m_start != src_range.m_finish)
+	    return "macro expansion";
+	}
+      else
+	{
+	  if (src_range.m_start >= LINE_MAP_MAX_LOCATION_WITH_COLS)
+	    /* If so, we can't reliably determine where the token started within
+	       its line.  */
+	    return "range starts after LINE_MAP_MAX_LOCATION_WITH_COLS";
+
+	  if (src_range.m_finish >= LINE_MAP_MAX_LOCATION_WITH_COLS)
+	    /* If so, we can't reliably determine where the token finished
+	       within its line.  */
+	    return "range ends after LINE_MAP_MAX_LOCATION_WITH_COLS";
+	}
 
       expanded_location start
-	= expand_location_to_spelling_point (src_range.m_start);
+	= expand_location_to_spelling_point (src_range.m_start,
+					     LOCATION_ASPECT_START);
       expanded_location finish
-	= expand_location_to_spelling_point (src_range.m_finish);
+	= expand_location_to_spelling_point (src_range.m_finish,
+					     LOCATION_ASPECT_FINISH);
       if (start.file != finish.file)
 	return "range endpoints are in different files";
       if (start.line != finish.line)

gcc/input.h

@@ -85,7 +85,10 @@ class char_span
 extern char_span location_get_source_line (const char *file_path, int line);
 
 extern bool location_missing_trailing_newline (const char *file_path);
-extern expanded_location expand_location_to_spelling_point (source_location);
+extern expanded_location
+expand_location_to_spelling_point (source_location,
+				   enum location_aspect aspect
+				     = LOCATION_ASPECT_CARET);
 extern source_location expansion_point_location_if_in_system_header (source_location);
 extern source_location expansion_point_location (source_location);
 

gcc/testsuite/ChangeLog

 2018-10-05  David Malcolm  <dmalcolm@redhat.com>
 
+	PR c++/56856
+	* g++.dg/ext/builtin4.C: Set expected location for warning to the
+	correct location within the format string.
+	* g++.dg/plugin/plugin.exp (plugin_test_list): Add the plugin and
+	files for testing locations within string literal locations from
+	the C frontend.
+	* g++.dg/warn/Wformat-method.C: New test.
+	* g++.dg/warn/Wformat-pr71863.C: New test.
+	* g++.dg/warn/Wformat-ranges-c++11.C: New test.
+	* g++.dg/warn/Wformat-ranges.C: New test, based on
+	gcc.dg/format/diagnostic-ranges.c.
+	* gcc.dg/plugin/diagnostic-test-string-literals-1.c
+	(test_multitoken_macro): Generalize expected output to work with
+	both C and C++.
+	* gcc.dg/plugin/diagnostic-test-string-literals-2.c
+	(test_stringified_token_1): Likewise.
+	(test_stringified_token_3): Likewise.
+
+2018-10-05  David Malcolm  <dmalcolm@redhat.com>
+
 	* lib/multiline.exp (proc dg-end-multiline-output): Check argument
 	count.  If there's a 3rd argument, use dg-process-target on it,
 	bailing out, or recording expected failures as "maybe_x".

gcc/testsuite/g++.dg/ext/builtin4.C

@@ -6,5 +6,5 @@
 extern "C" int printf(const char*,...);
 
 void foo() {
-  printf("%d"); 		// { dg-warning "expects a matching" }
+  printf("%d"); 		// { dg-warning "12: expects a matching" }
 }

gcc/testsuite/g++.dg/plugin/plugin.exp

@@ -67,6 +67,11 @@ set plugin_test_list [list \
 	  diagnostic-test-expressions-1.C } \
     { ../../gcc.dg/plugin/diagnostic_plugin_test_inlining.c \
 	  diagnostic-test-inlining-1.C } \
+    { ../../gcc.dg/plugin/diagnostic_plugin_test_string_literals.c \
+	  ../../gcc.dg/plugin/diagnostic-test-string-literals-1.c \
+	  ../../gcc.dg/plugin/diagnostic-test-string-literals-2.c \
+	  ../../gcc.dg/plugin/diagnostic-test-string-literals-3.c \
+	  ../../gcc.dg/plugin/diagnostic-test-string-literals-4.c } \
     { show_template_tree_color_plugin.c \
     	  show-template-tree-color.C \
     	  show-template-tree-color-labels.C \

gcc/testsuite/g++.dg/warn/Wformat-method.C

+// { dg-options "-Wformat -fdiagnostics-show-caret" }
+
+class logger
+{
+public:
+  void log (const char *fmt, ...) __attribute__((format (printf, 2, 3)));
+};
+
+void test ()
+{
+  logger out;
+  out.log ("before %s after", 42); // { dg-warning "argument 3 has type 'int'" }
+  /* { dg-begin-multiline-output "" }
+   out.log ("before %s after", 42);
+                    ~^         ~~
+                     |         |
+                     char*     int
+                    %d
+   { dg-end-multiline-output "" } */
+}
+
+template <typename T>
+class logger_2
+{
+public:
+  void log (const char *fmt, ...) __attribute__((format (printf, 2, 3)));
+};
+
+void test_2 ()
+{
+  logger_2<int> out;
+  out.log ("before %s after", 42); // { dg-warning "argument 3 has type 'int'" }
+  /* { dg-begin-multiline-output "" }
+   out.log ("before %s after", 42);
+                    ~^         ~~
+                     |         |
+                     char*     int
+                    %d
+   { dg-end-multiline-output "" } */
+}

gcc/testsuite/g++.dg/warn/Wformat-pr71863.C

+// { dg-options "-Wformat -fdiagnostics-show-caret" }
+
+void test_1 (void)
+{
+  __builtin_printf ("%s%s", 42, 43); // { dg-warning "argument 2 has type 'int'" }
+  // { dg-warning "argument 3 has type 'int'" "" { target *-*-* } .-1 }
+  /* { dg-begin-multiline-output "" }
+   __builtin_printf ("%s%s", 42, 43);
+                      ~^     ~~
+                       |     |
+                       char* int
+                      %d
+     { dg-end-multiline-output "" } */
+  /* { dg-begin-multiline-output "" }
+   __builtin_printf ("%s%s", 42, 43);
+                        ~^       ~~
+                         |       |
+                         char*   int
+                        %d
+     { dg-end-multiline-output "" } */
+}
+
+void test_2 (void)
+{
+  __builtin_printf ("before %s after", 6 * 7); // { dg-warning "argument 2 has type 'int'" }
+  /* { dg-begin-multiline-output "" }
+   __builtin_printf ("before %s after", 6 * 7);
+                             ~^         ~~~~~
+                              |           |
+                              char*       int
+                             %d
+     { dg-end-multiline-output "" } */
+}

gcc/testsuite/g++.dg/warn/Wformat-ranges-c++11.C

+// { dg-do compile { target c++11 } }
+/* { dg-options "-Wformat -fdiagnostics-show-caret" } */
+
+/* C++11-specific format tests. */
+
+#define printf __builtin_printf
+
+void test_u8 (const char *msg)
+{
+  printf(u8"hello %i", msg);/* { dg-warning "format '%i' expects argument of type 'int', but argument 2 has type 'const char\\*' " } */
+/* { dg-begin-multiline-output "" }
+   printf(u8"hello %i", msg);
+                   ~^   ~~~
+                    |   |
+                    int const char*
+                   %s
+   { dg-end-multiline-output "" } */
+}

gcc/testsuite/gcc.dg/format/diagnostic-ranges.c

@@ -314,7 +314,8 @@ void test_macro_2 (const char *msg)
 
 void test_macro_3 (const char *msg)
 {
-#define FMT_STRING "hello %i world" /* { dg-warning "20: format '%i' expects argument of type 'int', but argument 2 has type 'const char \\*' " } */
+#define FMT_STRING "hello %i world" /* { dg-line test_macro_3_macro_line } */
+  /* { dg-warning "20: format '%i' expects argument of type 'int', but argument 2 has type 'const char \\*'" "" { target *-*-*} .-1 } */
   printf(FMT_STRING, msg);  /* { dg-message "10: in expansion of macro 'FMT_STRING" } */
 /* { dg-begin-multiline-output "" }
  #define FMT_STRING "hello %i world"
@@ -324,6 +325,14 @@ void test_macro_3 (const char *msg)
    printf(FMT_STRING, msg);
           ^~~~~~~~~~
    { dg-end-multiline-output "" } */
+/* { dg-message "28: format string is defined here" "" { target *-*-* } test_macro_3_macro_line } */
+/* { dg-begin-multiline-output "" }
+ #define FMT_STRING "hello %i world"
+                           ~^
+                            |
+                            int
+                           %s
+   { dg-end-multiline-output "" } */
 #undef FMT_STRING
 }
 

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

@@ -251,7 +251,11 @@ test_multitoken_macro (void)
 /* { dg-begin-multiline-output "" }
  #define RANGE ("0123456789")
                ^~~~~~~~~~~~~~
-   { dg-end-multiline-output "" } */
+   { dg-end-multiline-output "" { target c } } */
+/* { dg-begin-multiline-output "" }
+ #define RANGE ("0123456789")
+               ~^~~~~~~~~~~~~
+   { dg-end-multiline-output "" { target c++ } } */
 /* { dg-begin-multiline-output "" }
    __emit_string_literal_range (RANGE, 4, 3, 6);
                                 ^~~~~

gcc/testsuite/gcc.dg/plugin/diagnostic-test-string-literals-2.c

@@ -12,7 +12,7 @@ test_stringified_token_1 (int x)
 {
 #define STRINGIFY(EXPR) #EXPR
 
-  __emit_string_literal_range (STRINGIFY(x > 0), /* { dg-error "unable to read substring location: macro expansion" } */
+  __emit_string_literal_range (STRINGIFY(x > 0), /* { dg-error "macro expansion|cpp_interpret_string_1 failed" } */
                                0, 0, 4);
 
 #undef STRINGIFY
@@ -43,7 +43,7 @@ test_stringified_token_3 (int x)
 #define XSTR(s) STR(s)
 #define STR(s) #s
 #define FOO 123456789
-  __emit_string_literal_range (XSTR (FOO), /* { dg-error "unable to read substring location: macro expansion" } */
+  __emit_string_literal_range (XSTR (FOO), /* { dg-error "macro expansion|cpp_interpret_string_1 failed" } */
                                2, 2, 3);
 
 #undef XSTR