On Mon, 30 Jul 2018, Tom de Vries wrote:
> Hi,
>
> Consider test.C compiled at -O0 -g:
> ...
> class string {
> public:
> string (const char *p) { this->p = p ; }
> string (const string &s) { this->p = s.p; }
>
> private:
> const char *p;
> };
>
> class foo {
> public:
> foo (string dir_hint) {}
> };
>
> int
> main (void)
> {
> std::string s = "This is just a string";
> foo bar(s);
> return 0;
> }
> ...
>
> When parsing foo::foo, the dir_hint parameter gets a DECL_ARG_TYPE of
> 'struct string & restrict'. Then during finish_struct, we call
> clone_constructors_and_destructors and create clones for foo::foo, and
> set the DECL_ARG_TYPE in the same way.
>
> Later on, during finish_function, cp_genericize is called for the original
> foo::foo, which sets the type of parm dir_hint to DECL_ARG_TYPE, and sets
> DECL_BY_REFERENCE of dir_hint to 1.
>
> After that, during maybe_clone_body update_cloned_parm is called with:
> ...
> (gdb) call debug_generic_expr (parm.typed.type)
> struct string & restrict
> (gdb) call debug_generic_expr (cloned_parm.typed.type)
> struct string
> ...
> The type of the cloned_parm is then set to the type of parm, but
> DECL_BY_REFERENCE is not set.
>
> When doing cp_genericize for the clone later on,
> TREE_ADDRESSABLE (TREE_TYPE ()) is no longer true for the updated type of
> the parm, so DECL_BY_REFERENCE is not set there either.
>
> This patch fixes the problem by copying DECL_BY_REFERENCE in
> update_cloned_parm.
>
> Build and reg-tested on x86_64.
>
> OK for trunk?
Thanks for tracking this down. It looks OK to me but please leave
Jason and Nathan a day to comment.
Otherwise OK for trunk and also for branches after a while.
Thanks,
Richard.
> Thanks,
> - Tom
>
> [c++] Fix DECL_BY_REFERENCE of clone parms
>
> 2018-07-30 Tom de Vries <tdevr...@suse.de>
>
> PR debug/86687
> * optimize.c (update_cloned_parm): Copy DECL_BY_REFERENCE.
>
> * g++.dg/guality/pr86687.C: New test.
>
> ---
> gcc/cp/optimize.c | 2 ++
> gcc/testsuite/g++.dg/guality/pr86687.C | 28 ++++++++++++++++++++++++++++
> 2 files changed, 30 insertions(+)
>
> diff --git a/gcc/cp/optimize.c b/gcc/cp/optimize.c
> index 0e9b84ed8a4..3923a5fc6c4 100644
> --- a/gcc/cp/optimize.c
> +++ b/gcc/cp/optimize.c
> @@ -46,6 +46,8 @@ update_cloned_parm (tree parm, tree cloned_parm, bool first)
> /* We may have taken its address. */
> TREE_ADDRESSABLE (cloned_parm) = TREE_ADDRESSABLE (parm);
>
> + DECL_BY_REFERENCE (cloned_parm) = DECL_BY_REFERENCE (parm);
> +
> /* The definition might have different constness. */
> TREE_READONLY (cloned_parm) = TREE_READONLY (parm);
>
> diff --git a/gcc/testsuite/g++.dg/guality/pr86687.C
> b/gcc/testsuite/g++.dg/guality/pr86687.C
> new file mode 100644
> index 00000000000..140a6fce596
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/guality/pr86687.C
> @@ -0,0 +1,28 @@
> +// PR debug/86687
> +// { dg-do run }
> +// { dg-options "-g" }
> +
> +class string {
> +public:
> + string (int p) { this->p = p ; }
> + string (const string &s) { this->p = s.p; }
> +
> + int p;
> +};
> +
> +class foo {
> +public:
> + foo (string dir_hint) {
> + p = dir_hint.p; // { dg-final { gdb-test . "dir_hint.p" 3 } }
> + }
> +
> + int p;
> +};
> +
> +int
> +main (void)
> +{
> + string s = 3;
> + foo bar(s);
> + return !(bar.p == 3);
> +}
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
