Re: [C PATCH] Avoid incorrect warning for volatile in compound expressions [PR 98260]

[Joseph Myers]

On Sun, 13 Dec 2020, Uecker, Martin wrote:

> 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]

OK.

-- 
Joseph S. Myers
jos...@codesourcery.com

Re: [C PATCH] Avoid incorrect warning for volatile in compound expressions [PR 98260]

[Martin Sebor via Gcc-patches]

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  
 
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 000..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" } */
+}
+
+

[C PATCH] Avoid incorrect warning for volatile in compound expressions [PR 98260]

[Uecker, Martin]

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  

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 000..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" } */
+}
+
+