I like to ping this patch.
Am Freitag, dem 09.08.2024 um 10:20 +0200 schrieb Martin Uecker:
> 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" } */
> > +}
> >
>
