On 12/13/20 9:12 AM, Uecker, Martin wrote:
Here is a patch that fixes an incorrect warning for volatile
that appeared with the lvalue change.
It's helpful to mention the bug id in the first line of the regression
tests committed with the fix. (No need to repost the patch just with
that change.)
Martin
-- 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" } */
+}
+
+
