ok?
Am Samstag, dem 29.06.2024 um 20:30 +0200 schrieb Martin Uecker:
> Probably not entirely fool-proof when using statement
> expressions in initializers, but should be good enough.
>
>
> Bootstrapped and regression tested on x86_64.
>
>
>
> c: Diagnose declarations that are used only in their own initializer
> [PR115027]
>
> Track the declaration that is currently being initialized and do not
> mark it as read when it is used in its own initializer. This then
> allows it to be diagnosed as set-but-unused when it is not used
> elsewhere.
>
> PR c/115027
>
> gcc/c/
> * c-tree.h (in_decl_init): Declare variable.
> * c-parser.cc (c_parser_initializer): Record decl being
> initialized.
> * c-typeck.cc (in_decl_init): Defintie variable.
> (mark_exp_read): Ignore decl currently being initialized.
>
> gcc/testsuite/
> * gcc.dg/pr115027.c: New test.
>
> diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
> index 8c4e697a4e1..46060665115 100644
> --- a/gcc/c/c-parser.cc
> +++ b/gcc/c/c-parser.cc
> @@ -6126,11 +6126,14 @@ c_parser_type_name (c_parser *parser, bool alignas_ok)
> static struct c_expr
> c_parser_initializer (c_parser *parser, tree decl)
> {
> + struct c_expr ret;
> + tree save = in_decl_init;
> + in_decl_init = decl;
> +
> if (c_parser_next_token_is (parser, CPP_OPEN_BRACE))
> - return c_parser_braced_init (parser, NULL_TREE, false, NULL, decl);
> + ret = c_parser_braced_init (parser, NULL_TREE, false, NULL, decl);
> else
> {
> - struct c_expr ret;
> location_t loc = c_parser_peek_token (parser)->location;
> ret = c_parser_expr_no_commas (parser, NULL);
> if (decl != error_mark_node && C_DECL_VARIABLE_SIZE (decl))
> @@ -6154,8 +6157,9 @@ c_parser_initializer (c_parser *parser, tree decl)
> || C_DECL_DECLARED_CONSTEXPR (COMPOUND_LITERAL_EXPR_DECL
> (ret.value))))
> ret = convert_lvalue_to_rvalue (loc, ret, true, true, true);
> - return ret;
> }
> + in_decl_init = save;
> + return ret;
> }
>
> /* The location of the last comma within the current initializer list,
> diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
> index 15da875a029..8013963b06d 100644
> --- a/gcc/c/c-tree.h
> +++ b/gcc/c/c-tree.h
> @@ -740,6 +740,8 @@ extern int in_typeof;
> extern bool c_in_omp_for;
> extern bool c_omp_array_section_p;
>
> +extern tree in_decl_init;
> +
> extern tree c_last_sizeof_arg;
> extern location_t c_last_sizeof_loc;
>
> diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
> index 455dc374b48..34279dc1d1a 100644
> --- a/gcc/c/c-typeck.cc
> +++ b/gcc/c/c-typeck.cc
> @@ -73,6 +73,9 @@ int in_sizeof;
> /* The level of nesting inside "typeof". */
> int in_typeof;
>
> +/* When inside an initializer, this is set to the decl being initialized. */
> +tree in_decl_init;
> +
> /* True when parsing OpenMP loop expressions. */
> bool c_in_omp_for;
>
> @@ -2047,7 +2050,8 @@ mark_exp_read (tree exp)
> {
> case VAR_DECL:
> case PARM_DECL:
> - DECL_READ_P (exp) = 1;
> + if (exp != in_decl_init)
> + DECL_READ_P (exp) = 1;
> break;
> case ARRAY_REF:
> case COMPONENT_REF:
> diff --git a/gcc/testsuite/gcc.dg/pr115027.c b/gcc/testsuite/gcc.dg/pr115027.c
> new file mode 100644
> index 00000000000..ac2699f8392
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr115027.c
> @@ -0,0 +1,8 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Wunused-but-set-variable" } */
> +
> +void f(void)
> +{
> + struct foo { void *p; };
> + struct foo g = { &g }; /* { dg-warning "set but not used" } */
> +}
>
