On Thu, Feb 20, 2014 at 05:52:09PM +0530, Prathamesh Kulkarni wrote:
> Show column number of left operand instead of comma operator
> in the warning "left-hand operand of comma expression has no effect"
>
> Example:
> ax.c:4:6: warning: left-hand operand of comma expression has no effect
> [-Wunused-value]
> x , y;
> ^
Perhaps a PR should be opened for this.
> Instead of comma operator, show location of left-operand:
> ax.c:4:3: warning: left-hand operand of comma expression has no effect
> [-Wunused-value]
> x , y;
> ^
But this patch only handles LHS of comma expression, and not RHS,
right? IMHO we should do both at the same time (that would be
for 5.0 I'd say).
> Bootstrapped on x86_64-unknown-linux-gnu.
>
> [gcc/c]
> * c-parser.c (c_parser_expression): Pass tloc instead of loc to
> build_compound_expr.
>
> [gcc/testsuite]
> * gcc.dg/Wunused-value-4.c: New test case.
>
> I am not able to figure out, how to write test-case that
> raises multiple warnings. example: (void) x, y, z.
> I tried this:
> /* { dg-warning "8:left-hand operand of comma expression has no effect
> |11:left-hand operand of comma expression has no
> effect" } */
> x has column number 8 and y has column number 11, but this doesn't
> seem to work (the patch works correctly).
For this you'll need a second dg-warning that specifies the line, so
e.g. something like
/* { dg-warning "11:left-hand operand of comma expression has no effect" "" {
target *-*-* } 10 } */
(Not reviewing the patch per se now.)
> Thanks and Regards,
> Prathamesh
> Index: gcc/c/c-parser.c
> ===================================================================
> --- gcc/c/c-parser.c (revision 207916)
> +++ gcc/c/c-parser.c (working copy)
> @@ -7838,7 +7838,6 @@ c_parser_expression (c_parser *parser)
> {
> struct c_expr next;
> tree lhsval;
> - location_t loc = c_parser_peek_token (parser)->location;
> location_t expr_loc;
> c_parser_consume_token (parser);
> expr_loc = c_parser_peek_token (parser)->location;
> @@ -7849,9 +7848,10 @@ c_parser_expression (c_parser *parser)
> mark_exp_read (lhsval);
> next = c_parser_expr_no_commas (parser, NULL);
> next = convert_lvalue_to_rvalue (expr_loc, next, true, false);
> - expr.value = build_compound_expr (loc, expr.value, next.value);
> + expr.value = build_compound_expr (tloc, expr.value, next.value);
> expr.original_code = COMPOUND_EXPR;
> expr.original_type = next.original_type;
> + tloc = expr_loc;
> }
> return expr;
> }
> Index: gcc/testsuite/gcc.dg/Wunused-value-4.c
> ===================================================================
> --- gcc/testsuite/gcc.dg/Wunused-value-4.c (revision 0)
> +++ gcc/testsuite/gcc.dg/Wunused-value-4.c (working copy)
> @@ -0,0 +1,12 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Wunused-value" } */
> +
> +void foo(int x);
> +
> +int a[10];
> +
> +void f(void)
> +{
> + foo ((1, 2)); /* { dg-warning "9: left-hand operand of
> comma expression has no effect" } */
> + a[0x03, 004] = 1992; /* { dg-warning "5: left-hand operand of
> comma expression has no effect" } */
> +}
Marek
