Here is a patch that fixes an incorrect warning for volatile
that appeared with the lvalue change.
-- Martin
C: Avoid incorrect warning for volatile in compound expressions [PR98260]
2020-12-12 Martin Uecker <muec...@gwdg.de>
gcc/c/
PR c/98260
* c-parser.c (c_parser_expression): Look into
nop expression when marking expressions as read.
gcc/testsuite/
PR c/98260
* gcc.dg/unused-9.c: New test.
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 87ee8f47806..1388a60c495 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -10615,8 +10615,14 @@ c_parser_expression (c_parser *parser)
c_parser_consume_token (parser);
expr_loc = c_parser_peek_token (parser)->location;
lhsval = expr.value;
- while (TREE_CODE (lhsval) == COMPOUND_EXPR)
- lhsval = TREE_OPERAND (lhsval, 1);
+ while (TREE_CODE (lhsval) == COMPOUND_EXPR
+ || TREE_CODE (lhsval) == NOP_EXPR)
+ {
+ if (TREE_CODE (lhsval) == COMPOUND_EXPR)
+ lhsval = TREE_OPERAND (lhsval, 1);
+ else
+ lhsval = TREE_OPERAND (lhsval, 0);
+ }
if (DECL_P (lhsval) || handled_component_p (lhsval))
mark_exp_read (lhsval);
next = c_parser_expr_no_commas (parser, NULL);
diff --git a/gcc/testsuite/gcc.dg/unused-9.c b/gcc/testsuite/gcc.dg/unused-9.c
new file mode 100644
index 00000000000..b32f7ef6c03
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/unused-9.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-Wunused" } */
+
+
+void g(void)
+{
+ int i = 0;
+ volatile int x;
+ (x, i++); /* { dg-bogus "set but not used" } */
+}
+
+
