Here is a patch to reduce false positives in _Generic.
Bootstrapped and regression tested on x86_64-linux.
Martin
c: _Generic should not warn in non-active branches [PR68193,PR97100]
To avoid false diagnostics, use c_inhibit_evaluation_warnings when
a generic association is known to match during parsing. We may still
generate false positives if the default branch comes earler than
a specific association that matches.
PR c/68193
PR c/97100
gcc/c/:
* c-parser.cc (c_parser_generic_selection): Inhibit evaluation
warnings branches that are known not be taken during parsing.
gcc/testsuite/ChangeLog:
* gcc.dg/pr68193.c: New test.
diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
index 24a6eb6e459..d1863b301e0 100644
--- a/gcc/c/c-parser.cc
+++ b/gcc/c/c-parser.cc
@@ -9350,7 +9350,17 @@ c_parser_generic_selection (c_parser *parser)
return error_expr;
}
+ bool match = assoc.type == NULL_TREE
+ || comptypes (assoc.type, selector_type);
+
+ if (!match)
+ c_inhibit_evaluation_warnings++;
+
assoc.expression = c_parser_expr_no_commas (parser, NULL);
+
+ if (!match)
+ c_inhibit_evaluation_warnings--;
+
if (assoc.expression.value == error_mark_node)
{
c_parser_skip_until_found (parser, CPP_CLOSE_PAREN, NULL);
@@ -9387,7 +9397,7 @@ c_parser_generic_selection (c_parser *parser)
match_found = associations.length ();
}
}
- else if (comptypes (assoc.type, selector_type))
+ else if (match)
{
if (match_found < 0 || matched_assoc.type == NULL_TREE)
{
diff --git a/gcc/testsuite/gcc.dg/pr68193.c b/gcc/testsuite/gcc.dg/pr68193.c
new file mode 100644
index 000..2267593e363
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr68193.c
@@ -0,0 +1,15 @@
+/* pr69193 */
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+int
+main (void)
+{
+ int i = 0;
+ int j = _Generic (i,
+ int: 0,
+ long int: (i = (long int) 9223372036854775808UL));
+ return i + j;
+}
+
+
