Don't emit -Wxor-used-as-pow on macro expansions [PR107002]

PR c/107002 reports an assertion failure from deep inside the
diagnostic_shows_locus when attempting to print fix-it hints relating
to -Wxor-used-as-pow.  The case involves macro expansions with
-ftrack-macro-expansion=0.

It doesn't seem to make much sense to emit this warning for macro
expansions, so this patch updates the warning not to (which seems
to also be clang's behavior).  The patch also adds some bulletproofing
to diagnostic-show-locus.cc to be more robust against such invalid
fix-it hints.

Doing so fixes the ICE.

gcc/c-family/ChangeLog:
	PR c/107002
	* c-common.h (check_for_xor_used_as_pow): Add "rhs_loc" param.
	* c-warn.cc (check_for_xor_used_as_pow): Add "rhs_loc" param.
	Reject cases where involving macro expansions.

gcc/c/ChangeLog:
	PR c/107002
	* c-typeck.cc (parser_build_binary_op): Update for new param of
	check_for_xor_used_as_pow.

gcc/cp/ChangeLog:
	PR c/107002
	* parser.cc (cp_parser_binary_expression): Update for new param of
	check_for_xor_used_as_pow.

gcc/ChangeLog:
	PR c/107002
	* diagnostic-show-locus.cc (column_range::column_range): Factor
	out assertion conditional into...
	(column_range::valid_p): ...this new function.
	(line_corrections::add_hint): Don't attempt to consolidate hints
	if it would lead to invalid column_range instances.

gcc/testsuite/ChangeLog:
	PR c/107002
	* c-c++-common/Wxor-used-as-pow-1.c: Add macro test.
	* c-c++-common/Wxor-used-as-pow-pr107002-0.c: New test.
	* c-c++-common/Wxor-used-as-pow-pr107002-1.c: New test.
	* c-c++-common/Wxor-used-as-pow-pr107002-2.c: New test.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>

2 files changed, 20 insertions, 5 deletions

diff --git a/gcc/c-family/c-common.h b/gcc/c-family/c-common.h
index e128e3e..f96350b 100644
--- a/gcc/c-family/c-common.h
+++ b/gcc/c-family/c-common.h
@@ -1524,7 +1524,7 @@ extern void warn_for_multistatement_macros (location_t, location_t,
 
 extern void check_for_xor_used_as_pow (location_t lhs_loc, tree lhs_val,
 				       location_t operator_loc,
-				       tree rhs_val);
+				       location_t rhs_loc, tree rhs_val);
 
 /* In c-attribs.cc.  */
 extern bool attribute_takes_identifier_p (const_tree);
diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
index ccbede9..9ac43a1 100644
--- a/gcc/c-family/c-warn.cc
+++ b/gcc/c-family/c-warn.cc
@@ -3835,14 +3835,15 @@ do_warn_array_compare (location_t location, tree_code code, tree op0, tree op1)
     }
 }
 
-/* Given LHS_VAL ^ RHS_VAL, where LHS_LOC is the location of the LHS and
-   OPERATOR_LOC is the location of the ^, complain with -Wxor-used-as-pow
-   if it looks like the user meant exponentiation rather than xor.  */
+/* Given LHS_VAL ^ RHS_VAL, where LHS_LOC is the location of the LHS,
+   OPERATOR_LOC is the location of the ^, and RHS_LOC the location of the
+   RHS, complain with -Wxor-used-as-pow if it looks like the user meant
+   exponentiation rather than xor.  */
 
 void
 check_for_xor_used_as_pow (location_t lhs_loc, tree lhs_val,
 			   location_t operator_loc,
-			   tree rhs_val)
+			   location_t rhs_loc, tree rhs_val)
 {
   /* Only complain if both args are non-negative integer constants that fit
      in uhwi.  */
@@ -3859,6 +3860,20 @@ check_for_xor_used_as_pow (location_t lhs_loc, tree lhs_val,
   binary_op_rich_location loc (operator_loc,
 			       lhs_val, rhs_val, false);
 
+  /* Reject cases where we don't have 3 distinct locations.
+     This can happen e.g. due to macro expansion with
+     -ftrack-macro-expansion=0 */
+  if (!(lhs_loc != operator_loc
+	&& lhs_loc != rhs_loc
+	&& operator_loc != rhs_loc))
+    return;
+
+  /* Reject cases in which any of the locations came from a macro.  */
+  if (from_macro_expansion_at (lhs_loc)
+      || from_macro_expansion_at (operator_loc)
+      || from_macro_expansion_at (rhs_loc))
+    return;
+
   /* If we issue fix-it hints with the warning then we will also issue a
      note suggesting how to suppress the warning with a different change.
      These proposed changes are incompatible.  */