On Wed, Aug 24, 2016 at 04:03:10PM -0400, David Malcolm wrote:
> I was thinking about maybe:
>   rich_location::add_fixit_insert_after_caret (source_location loc)
> which would add it immediately after the *caret* location of loc - as
> opposed to after the *finish* location of loc, or maybe just:
>   rich_location::add_fixit_insert_after (source_location loc)
> which
> would take into account the finish location of loc.
> 
> Having a helper in rich_location for this would be good, for protecting 
> against cases where some of the tokens are in a macro expansion, and others 
> aren't (I think fix-its within a rich_location ought to be atomic: if some 
> can't be applied, none should be).  I'd rather have the rich_location 
> machinery care about these awkward issues in one place, rather than force 
> every diagnostic to do it.
 
Yes, sure.

> I already have the beginnings of some fixit validation code written (but not 
> posted), so maybe you should go ahead and post the patch as-is, and we can 
> move the relevant parts into a helper as a followup?

Ok, how about this one?

Bootstrapped/regtested on x86_64-linux, ok for trunk?

2016-08-25  Marek Polacek  <pola...@redhat.com>
            David Malcolm  <dmalc...@redhat.com>

        * c-common.c (warn_logical_not_parentheses): Print fixit hints.
        * c-common.h (warn_logical_not_parentheses): Update declaration.

        * c-typeck.c (parser_build_binary_op): Pass LHS to
        warn_logical_not_parentheses.

        * parser.c (cp_parser_binary_expression): Pass LHS to
        warn_logical_not_parentheses.

        * c-c++-common/Wlogical-not-parentheses-2.c: New test.

diff --git gcc/c-family/c-common.c gcc/c-family/c-common.c
index 3feb910..001070d 100644
--- gcc/c-family/c-common.c
+++ gcc/c-family/c-common.c
@@ -1485,7 +1485,7 @@ warn_tautological_cmp (location_t loc, enum tree_code 
code, tree lhs, tree rhs)
 
 void
 warn_logical_not_parentheses (location_t location, enum tree_code code,
-                             tree rhs)
+                             tree lhs, tree rhs)
 {
   if (TREE_CODE_CLASS (code) != tcc_comparison
       || TREE_TYPE (rhs) == NULL_TREE
@@ -1498,9 +1498,21 @@ warn_logical_not_parentheses (location_t location, enum 
tree_code code,
       && integer_zerop (rhs))
     return;
 
-  warning_at (location, OPT_Wlogical_not_parentheses,
-             "logical not is only applied to the left hand side of "
-             "comparison");
+  if (warning_at (location, OPT_Wlogical_not_parentheses,
+                 "logical not is only applied to the left hand side of "
+                 "comparison")
+      && EXPR_HAS_LOCATION (lhs))
+    {
+      location_t lhs_loc = EXPR_LOCATION (lhs);
+      rich_location richloc (line_table, lhs_loc);
+      richloc.add_fixit_insert (lhs_loc, "(");
+      location_t finish = get_finish (lhs_loc);
+      location_t next_loc
+       = linemap_position_for_loc_and_offset (line_table, finish, 1);
+      richloc.add_fixit_insert (next_loc, ")");
+      inform_at_rich_loc (&richloc, "add parentheses around left hand side "
+                         "expression to silence this warning");
+    }
 }
 
 /* Warn if EXP contains any computations whose results are not used.
diff --git gcc/c-family/c-common.h gcc/c-family/c-common.h
index bc22baa..42ce969 100644
--- gcc/c-family/c-common.h
+++ gcc/c-family/c-common.h
@@ -847,7 +847,8 @@ extern void overflow_warning (location_t, tree);
 extern bool warn_if_unused_value (const_tree, location_t);
 extern void warn_logical_operator (location_t, enum tree_code, tree,
                                   enum tree_code, tree, enum tree_code, tree);
-extern void warn_logical_not_parentheses (location_t, enum tree_code, tree);
+extern void warn_logical_not_parentheses (location_t, enum tree_code, tree,
+                                         tree);
 extern void warn_tautological_cmp (location_t, enum tree_code, tree, tree);
 extern void check_main_parameter_types (tree decl);
 extern bool c_determine_visibility (tree);
diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
index bc8728a..2f8d611 100644
--- gcc/c/c-typeck.c
+++ gcc/c/c-typeck.c
@@ -3696,7 +3696,7 @@ parser_build_binary_op (location_t location, enum 
tree_code code,
          while (1);
        }
       if (TREE_CODE (TREE_TYPE (t)) != BOOLEAN_TYPE)
-       warn_logical_not_parentheses (location, code, arg2.value);
+       warn_logical_not_parentheses (location, code, arg1.value, arg2.value);
     }
 
   /* Warn about comparisons against string literals, with the exception
diff --git gcc/cp/parser.c gcc/cp/parser.c
index 690e928..d54cf8a 100644
--- gcc/cp/parser.c
+++ gcc/cp/parser.c
@@ -8922,7 +8922,7 @@ cp_parser_binary_expression (cp_parser* parser, bool 
cast_p,
              || TREE_TYPE (current.lhs) == NULL_TREE
              || TREE_CODE (TREE_TYPE (current.lhs)) != BOOLEAN_TYPE))
        warn_logical_not_parentheses (current.loc, current.tree_type,
-                                     maybe_constant_value (rhs));
+                                     current.lhs, maybe_constant_value (rhs));
 
       overload = NULL;
 
diff --git gcc/testsuite/c-c++-common/Wlogical-not-parentheses-2.c 
gcc/testsuite/c-c++-common/Wlogical-not-parentheses-2.c
index e69de29..ba8dce8 100644
--- gcc/testsuite/c-c++-common/Wlogical-not-parentheses-2.c
+++ gcc/testsuite/c-c++-common/Wlogical-not-parentheses-2.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-Wlogical-not-parentheses -fdiagnostics-show-caret" } */
+
+ /* Test fixit hints.  */
+
+int
+foo (int aaa, int bbb)
+{
+  int r = 0;
+  r += (!aaa) == bbb;
+  r += !aaa == bbb; /* { dg-warning "logical not is only applied" } */
+/* { dg-begin-multiline-output "" }
+   r += !aaa == bbb;
+             ^~
+   r += !aaa == bbb;
+        ^~~~
+        (   )
+   { dg-end-multiline-output "" } */
+  return r;
+}

        Marek

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