Preserving locations for variable-uses and constants (PR c++/43486)

This patch implements location wrapper nodes, preserving source locations
of the uses of variables and constants in various places in the
C++ frontend: at the arguments at callsites, and for typeid, alignof,
sizeof, and offsetof.

For example, it allows the C++ FE to underline the pertinent argument
for mismatching calls, for such expressions, improving:

extern int callee (int one, const char *two, float three);

int caller (int first, int second, float third)
{
  return callee (first, second, third);
}

from

test.cc: In function 'int caller(int, int, float)':
test.cc:5:38: error: invalid conversion from 'int' to 'const char*' [-fpermissive]
   return callee (first, second, third);
                                      ^
test.cc:1:41: note:   initializing argument 2 of 'int callee(int, const char*, float)'
 extern int callee (int one, const char *two, float three);
                             ~~~~~~~~~~~~^~~

to:

test.cc: In function 'int caller(int, int, float)':
test.cc:5:25: error: invalid conversion from 'int' to 'const char*' [-fpermissive]
   return callee (first, second, third);
                         ^~~~~~
test.cc:1:41: note:   initializing argument 2 of 'int callee(int, const char*, float)'
 extern int callee (int one, const char *two, float three);
                             ~~~~~~~~~~~~^~~

This is the combination of the following patches:

  "[PATCH 01/14] C++: preserve locations within build_address"
     https://gcc.gnu.org/ml/gcc-patches/2017-11/msg00883.html

  "[PATCH v2.4 of 02/14] Support for adding and stripping location_t wrapper nodes"
    https://gcc.gnu.org/ml/gcc-patches/2018-01/msg00591.html

  "[PATCH] Eliminate location wrappers in tree_nop_conversion/STRIP_NOPS"
    https://gcc.gnu.org/ml/gcc-patches/2017-12/msg01330.html

  "[PATCH v4 of 03/14] C++: add location_t wrapper nodes during parsing (minimal impl)"
    https://gcc.gnu.org/ml/gcc-patches/2018-01/msg00660.html

  "[PATCH 04/14] Update testsuite to show improvements"
    https://gcc.gnu.org/ml/gcc-patches/2017-11/msg00891.html

  "[v3 of 05/14] C++: handle locations wrappers when calling warn_for_memset"
    https://gcc.gnu.org/ml/gcc-patches/2017-12/msg01378.html

  "[PATCH 07/14] reject_gcc_builtin: strip any location wrappers"
    https://gcc.gnu.org/ml/gcc-patches/2017-11/msg00886.html

  "[v3 of PATCH 08/14] cp/tree.c: strip location wrappers in lvalue_kind"
    https://gcc.gnu.org/ml/gcc-patches/2017-12/msg01433.html

  "[PATCH 09/14] Strip location wrappers in null_ptr_cst_p"
    https://gcc.gnu.org/ml/gcc-patches/2017-11/msg00888.html

  "[PATCH 11/14] Handle location wrappers in string_conv_p"
    https://gcc.gnu.org/ml/gcc-patches/2017-11/msg00890.html

  "[PATCH 12/14] C++: introduce null_node_p"
    https://gcc.gnu.org/ml/gcc-patches/2017-11/msg00894.html

  "[v3 of PATCH 13/14] c-format.c: handle location wrappers"
    https://gcc.gnu.org/ml/gcc-patches/2017-12/msg01494.html

  "[PATCH 14/14] pp_c_cast_expression: don't print casts for location wrappers"
    https://gcc.gnu.org/ml/gcc-patches/2017-11/msg00893.html

  "[v3 of PATCH 15/14] Use fold_for_warn in get_atomic_generic_size"
    https://gcc.gnu.org/ml/gcc-patches/2017-12/msg01380.html

  "[PATCH] Add selftest for "fold_for_warn (error_mark_node)""
    https://gcc.gnu.org/ml/gcc-patches/2017-12/msg01385.html

gcc/c-family/ChangeLog:
	PR c++/43486
	* c-common.c: Include "selftest.h".
	(get_atomic_generic_size): Perform the test for integral type
	before the range test for any integer constant, fixing indentation
	of braces.  Call fold_for_warn before testing for an INTEGER_CST.
	(reject_gcc_builtin): Strip any location wrapper from EXPR.
	(selftest::test_fold_for_warn): New function.
	(selftest::c_common_c_tests): New function.
	(selftest::c_family_tests): Call it, and
	selftest::c_pretty_print_c_tests.
	* c-common.h (selftest::c_pretty_print_c_tests): New decl.
	* c-format.c (check_format_arg): Convert VAR_P check to a
	fold_for_warn.
	* c-pretty-print.c: Include "selftest.h".
	(pp_c_cast_expression): Don't print casts for location wrappers.
	(selftest::assert_c_pretty_printer_output): New function.
	(ASSERT_C_PRETTY_PRINTER_OUTPUT): New macro.
	(selftest::test_location_wrappers): New function.
	(selftest::c_pretty_print_c_tests): New function.
	* c-warn.c (warn_for_memset): Call fold_for_warn on the arguments.

gcc/cp/ChangeLog:
	PR c++/43486
	* call.c (null_ptr_cst_p): Strip location wrappers when
	converting from '0' to a pointer type in C++11 onwards.
	(conversion_null_warnings): Replace comparison with null_node with
	call to null_node_p.
	(build_over_call): Likewise.
	* cp-gimplify.c (cp_fold): Remove the early bailout when
	processing_template_decl.
	* cp-lang.c (selftest::run_cp_tests): Call
	selftest::cp_pt_c_tests and selftest::cp_tree_c_tests.
	* cp-tree.h (cp_expr::maybe_add_location_wrapper): New method.
	(selftest::run_cp_tests): Move decl to bottom of file.
	(null_node_p): New inline function.
	(selftest::cp_pt_c_tests): New decl.
	(selftest::cp_tree_c_tests): New decl.
	* cvt.c (build_expr_type_conversion): Replace comparison with
	null_node with call to null_node_p.
	* error.c (args_to_string): Likewise.
	* except.c (build_throw): Likewise.
	* mangle.c (write_expression): Skip location wrapper nodes.
	* parser.c (literal_integer_zerop): New function.
	(cp_parser_postfix_expression): Call maybe_add_location_wrapper on
	the result for RID_TYPEID. Pass true for new "wrap_locations_p"
	param of cp_parser_parenthesized_expression_list.  When calling
	warn_for_memset, replace integer_zerop calls with
	literal_integer_zerop, eliminating the double logical negation
	cast to bool.  Eliminate the special-casing for CONST_DECL in
	favor of the fold_for_warn within warn_for_memset.
	(cp_parser_parenthesized_expression_list): Add "wrap_locations_p"
	param, defaulting to false.  Convert "expr" to a cp_expr, and call
	maybe_add_location_wrapper on it when wrap_locations_p is true.
	(cp_parser_unary_expression): Call maybe_add_location_wrapper on
	the result for RID_ALIGNOF and RID_SIZEOF.
	(cp_parser_builtin_offsetof): Likewise.
	* pt.c: Include "selftest.h".
	(tsubst_copy): Handle location wrappers.
	(tsubst_copy_and_build): Likewise.
	(build_non_dependent_expr): Likewise.
	(selftest::test_build_non_dependent_expr): New function.
	(selftest::cp_pt_c_tests): New function.
	* tree.c: Include "selftest.h".
	(lvalue_kind): Handle VIEW_CONVERT_EXPR location wrapper nodes.
	(selftest::test_lvalue_kind): New function.
	(selftest::cp_tree_c_tests): New function.
	* typeck.c (string_conv_p): Strip any location wrapper from "exp".
	(cp_build_binary_op): Replace comparison with null_node with call
	to null_node_p.
	(build_address): Use location of operand when building address
	expression.

gcc/testsuite/ChangeLog:
	PR c++/43486
	* g++.dg/diagnostic/param-type-mismatch.C: Update expected results
	to reflect that the arguments are correctly underlined.
	* g++.dg/plugin/diagnostic-test-expressions-1.C: Add test coverage
	for globals, params, locals and literals.
	(test_sizeof): Directly test the location of "sizeof", rather than
	when used in compound expressions.
	(test_alignof): Likewise for "alignof".
	(test_string_literals): Likewise for string literals.
	(test_numeric_literals): Likewise for numeric literals.
	(test_builtin_offsetof): Likewise for "__builtin_offsetof".
	(test_typeid): Likewise for typeid.
	(test_unary_plus): New.
	* g++.dg/warn/Wformat-1.C: Add tests of pointer arithmetic on
	format strings.

gcc/ChangeLog:
	PR c++/43486
	* tree-core.h: Document EXPR_LOCATION_WRAPPER_P's usage of
	"public_flag".
	* tree.c (tree_nop_conversion): Return true for location wrapper
	nodes.
	(maybe_wrap_with_location): New function.
	(selftest::check_strip_nops): New function.
	(selftest::test_location_wrappers): New function.
	(selftest::tree_c_tests): Call it.
	* tree.h (STRIP_ANY_LOCATION_WRAPPER): New macro.
	(maybe_wrap_with_location): New decl.
	(EXPR_LOCATION_WRAPPER_P): New macro.
	(location_wrapper_p): New inline function.
	(tree_strip_any_location_wrapper): New inline function.

From-SVN: r256448

6 files changed, 126 insertions, 16 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index e79d985..d6b6085 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,26 @@
+2018-01-10  David Malcolm  <dmalcolm@redhat.com>
+
+	PR c++/43486
+	* c-common.c: Include "selftest.h".
+	(get_atomic_generic_size): Perform the test for integral type
+	before the range test for any integer constant, fixing indentation
+	of braces.  Call fold_for_warn before testing for an INTEGER_CST.
+	(reject_gcc_builtin): Strip any location wrapper from EXPR.
+	(selftest::test_fold_for_warn): New function.
+	(selftest::c_common_c_tests): New function.
+	(selftest::c_family_tests): Call it, and
+	selftest::c_pretty_print_c_tests.
+	* c-common.h (selftest::c_pretty_print_c_tests): New decl.
+	* c-format.c (check_format_arg): Convert VAR_P check to a
+	fold_for_warn.
+	* c-pretty-print.c: Include "selftest.h".
+	(pp_c_cast_expression): Don't print casts for location wrappers.
+	(selftest::assert_c_pretty_printer_output): New function.
+	(ASSERT_C_PRETTY_PRINTER_OUTPUT): New macro.
+	(selftest::test_location_wrappers): New function.
+	(selftest::c_pretty_print_c_tests): New function.
+	* c-warn.c (warn_for_memset): Call fold_for_warn on the arguments.
+
 2018-01-03  Richard Sandiford  <richard.sandiford@linaro.org>
 	    Alan Hayward  <alan.hayward@arm.com>
 	    David Sherwood  <david.sherwood@arm.com>
diff --git a/gcc/c-family/c-common.c b/gcc/c-family/c-common.c
index 87bd326..097d192 100644
--- a/gcc/c-family/c-common.c
+++ b/gcc/c-family/c-common.c
@@ -48,6 +48,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimplify.h"
 #include "substring-locations.h"
 #include "spellcheck.h"
+#include "selftest.h"
 
 cpp_reader *parse_in;		/* Declared in c-pragma.h.  */
 
@@ -6737,8 +6738,15 @@ get_atomic_generic_size (location_t loc, tree function,
   for (x = n_param - n_model ; x < n_param; x++)
     {
       tree p = (*params)[x];
+      if (!INTEGRAL_TYPE_P (TREE_TYPE (p)))
+	{
+	  error_at (loc, "non-integer memory model argument %d of %qE", x + 1,
+		    function);
+	  return 0;
+	}
+      p = fold_for_warn (p);
       if (TREE_CODE (p) == INTEGER_CST)
-        {
+	{
 	  /* memmodel_base masks the low 16 bits, thus ignore any bits above
 	     it by using TREE_INT_CST_LOW instead of tree_to_*hwi.  Those high
 	     bits will be checked later during expansion in target specific
@@ -6748,14 +6756,7 @@ get_atomic_generic_size (location_t loc, tree function,
 			"invalid memory model argument %d of %qE", x + 1,
 			function);
 	}
-      else
-	if (!INTEGRAL_TYPE_P (TREE_TYPE (p)))
-	  {
-	    error_at (loc, "non-integer memory model argument %d of %qE", x + 1,
-		   function);
-	    return 0;
-	  }
-      }
+    }
 
   return size_0;
 }
@@ -7846,6 +7847,8 @@ reject_gcc_builtin (const_tree expr, location_t loc /* = UNKNOWN_LOCATION */)
   if (TREE_CODE (expr) == ADDR_EXPR)
     expr = TREE_OPERAND (expr, 0);
 
+  STRIP_ANY_LOCATION_WRAPPER (expr);
+
   if (TREE_TYPE (expr)
       && TREE_CODE (TREE_TYPE (expr)) == FUNCTION_TYPE
       && TREE_CODE (expr) == FUNCTION_DECL
@@ -8187,12 +8190,30 @@ maybe_suggest_missing_token_insertion (rich_location *richloc,
 
 namespace selftest {
 
+/* Verify that fold_for_warn on error_mark_node is safe.  */
+
+static void
+test_fold_for_warn ()
+{
+  ASSERT_EQ (error_mark_node, fold_for_warn (error_mark_node));
+}
+
+/* Run all of the selftests within this file.  */
+
+static void
+c_common_c_tests ()
+{
+  test_fold_for_warn ();
+}
+
 /* Run all of the tests within c-family.  */
 
 void
 c_family_tests (void)
 {
+  c_common_c_tests ();
   c_format_c_tests ();
+  c_pretty_print_c_tests ();
   c_spellcheck_cc_tests ();
 }
 
diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index 00bfe59..d090881 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1450,6 +1450,7 @@ namespace selftest {
   /* Declarations for specific families of tests within c-family,
      by source file, in alphabetical order.  */
   extern void c_format_c_tests (void);
+  extern void c_pretty_print_c_tests (void);
   extern void c_spellcheck_cc_tests (void);
 
   /* The entrypoint for running all of the above tests.  */
diff --git a/gcc/c-family/c-format.c b/gcc/c-family/c-format.c
index e071145..7a69d5a 100644
--- a/gcc/c-family/c-format.c
+++ b/gcc/c-family/c-format.c
@@ -1536,12 +1536,10 @@ check_format_arg (void *ctx, tree format_tree,
 
   location_t fmt_param_loc = EXPR_LOC_OR_LOC (format_tree, input_location);
 
-  if (VAR_P (format_tree))
-    {
-      /* Pull out a constant value if the front end didn't.  */
-      format_tree = decl_constant_value (format_tree);
-      STRIP_NOPS (format_tree);
-    }
+  /* Pull out a constant value if the front end didn't, and handle location
+     wrappers.  */
+  format_tree = fold_for_warn (format_tree);
+  STRIP_NOPS (format_tree);
 
   if (integer_zerop (format_tree))
     {
diff --git a/gcc/c-family/c-pretty-print.c b/gcc/c-family/c-pretty-print.c
index 6e4f85c..c9dd8ae 100644
--- a/gcc/c-family/c-pretty-print.c
+++ b/gcc/c-family/c-pretty-print.c
@@ -28,6 +28,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "attribs.h"
 #include "intl.h"
 #include "tree-pretty-print.h"
+#include "selftest.h"
 
 /* The pretty-printer code is primarily designed to closely follow
    (GNU) C and C++ grammars.  That is to be contrasted with spaghetti
@@ -1809,7 +1810,8 @@ pp_c_cast_expression (c_pretty_printer *pp, tree e)
     case FIX_TRUNC_EXPR:
     CASE_CONVERT:
     case VIEW_CONVERT_EXPR:
-      pp_c_type_cast (pp, TREE_TYPE (e));
+      if (!location_wrapper_p (e))
+	pp_c_type_cast (pp, TREE_TYPE (e));
       pp_c_cast_expression (pp, TREE_OPERAND (e, 0));
       break;
 
@@ -2400,3 +2402,65 @@ pp_c_tree_decl_identifier (c_pretty_printer *pp, tree t)
 
   pp_c_identifier (pp, name);
 }
+
+#if CHECKING_P
+
+namespace selftest {
+
+/* Selftests for pretty-printing trees.  */
+
+/* Verify that EXPR printed by c_pretty_printer is EXPECTED, using
+   LOC as the effective location for any failures.  */
+
+static void
+assert_c_pretty_printer_output (const location &loc, const char *expected,
+				tree expr)
+{
+  c_pretty_printer pp;
+  pp.expression (expr);
+  ASSERT_STREQ_AT (loc, expected, pp_formatted_text (&pp));
+}
+
+/* Helper function for calling assert_c_pretty_printer_output.
+   This is to avoid having to write SELFTEST_LOCATION.  */
+
+#define ASSERT_C_PRETTY_PRINTER_OUTPUT(EXPECTED, EXPR) \
+  SELFTEST_BEGIN_STMT						\
+    assert_c_pretty_printer_output ((SELFTEST_LOCATION),	\
+				    (EXPECTED),		\
+				    (EXPR));			\
+  SELFTEST_END_STMT
+
+/* Verify that location wrappers don't show up in pretty-printed output.  */
+
+static void
+test_location_wrappers ()
+{
+  /* VAR_DECL.  */
+  tree id = get_identifier ("foo");
+  tree decl = build_decl (UNKNOWN_LOCATION, VAR_DECL, id,
+			  integer_type_node);
+  tree wrapped_decl = maybe_wrap_with_location (decl, BUILTINS_LOCATION);
+  ASSERT_NE (wrapped_decl, decl);
+  ASSERT_C_PRETTY_PRINTER_OUTPUT ("foo", decl);
+  ASSERT_C_PRETTY_PRINTER_OUTPUT ("foo", wrapped_decl);
+
+  /* INTEGER_CST.  */
+  tree int_cst = build_int_cst (integer_type_node, 42);
+  tree wrapped_cst = maybe_wrap_with_location (int_cst, BUILTINS_LOCATION);
+  ASSERT_NE (wrapped_cst, int_cst);
+  ASSERT_C_PRETTY_PRINTER_OUTPUT ("42", int_cst);
+  ASSERT_C_PRETTY_PRINTER_OUTPUT ("42", wrapped_cst);
+}
+
+/* Run all of the selftests within this file.  */
+
+void
+c_pretty_print_c_tests ()
+{
+  test_location_wrappers ();
+}
+
+} // namespace selftest
+
+#endif /* CHECKING_P */
diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c
index 33cae8b..7d87c45 100644
--- a/gcc/c-family/c-warn.c
+++ b/gcc/c-family/c-warn.c
@@ -1868,6 +1868,9 @@ void
 warn_for_memset (location_t loc, tree arg0, tree arg2,
 		 int literal_zero_mask)
 {
+  arg0 = fold_for_warn (arg0);
+  arg2 = fold_for_warn (arg2);
+
   if (warn_memset_transposed_args
       && integer_zerop (arg2)
       && (literal_zero_mask & (1 << 2)) != 0