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Re: [PATCH][RFC] Instrument function exit with __builtin_unreachable in C++.
- From: Marek Polacek <polacek at redhat dot com>
- To: Martin Liška <mliska at suse dot cz>
- Cc: Jakub Jelinek <jakub at redhat dot com>, Jason Merrill <jason at redhat dot com>, gcc-patches List <gcc-patches at gcc dot gnu dot org>, Jonathan Wakely <jwakely at redhat dot com>
- Date: Wed, 18 Oct 2017 14:52:53 +0200
- Subject: Re: [PATCH][RFC] Instrument function exit with __builtin_unreachable in C++.
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On Wed, Oct 18, 2017 at 02:46:23PM +0200, Martin Liška wrote:
> On 10/12/2017 10:48 AM, Jakub Jelinek wrote:
> > On Thu, Oct 12, 2017 at 10:40:42AM +0200, Martin Liška wrote:
> >> --- a/gcc/cp/constexpr.c
> >> +++ b/gcc/cp/constexpr.c
> >> @@ -1175,7 +1175,12 @@ cxx_eval_builtin_function_call (const constexpr_ctx *ctx, tree t, tree fun,
> >> {
> >> new_call = build_call_array_loc (EXPR_LOCATION (t), TREE_TYPE (t),
> >> CALL_EXPR_FN (t), nargs, args);
> >> - error ("%q+E is not a constant expression", new_call);
> >> +
> >> + /* Do not allow__builtin_unreachable in constexpr function. */
> >> + if (DECL_FUNCTION_CODE (fun) == BUILT_IN_UNREACHABLE)
> >
> > As I said earlier, I think it would be better to differentiate between
> > explicit __builtin_unreachable and the implicitly added one from the patch.
> > So this could be done as
> > if (DECL_FUNCTION_CODE (fun) == BUILT_IN_UNREACHABLE
> > && EXPR_LOCATION (t) == BUILTINS_LOCATION)
> >
> >> + location_t loc = DECL_SOURCE_LOCATION (fndecl);
> >> + if (sanitize_flags_p (SANITIZE_RETURN, fndecl))
> >> + t = ubsan_instrument_return (loc);
> >> + else
> >> + t = build_call_expr_loc (loc, builtin_decl_explicit (BUILT_IN_UNREACHABLE),
> >
> > and here use BUILTINS_LOCATION instead of loc.
> > The code might be more readable by doing:
> > {
> > tree fndecl = builtin_decl_explicit (BUILT_IN_UNREACHABLE);
> > t = build_call_expr_loc (BUILTINS_LOCATION, fndecl, 0);
> > }
> >
> >> + 0);
> >> +
> >
> > Jakub
> >
>
> Hi.
>
> I'm sending updated version of the patch that should address it.
>
> Patch can bootstrap on ppc64le-redhat-linux and survives regression tests.
>
> Ready to be installed?
> Martin
> From 36f3f45d9fa42344261faf60bb3cfbe22ed262ac Mon Sep 17 00:00:00 2001
> From: marxin <mliska@suse.cz>
> Date: Thu, 12 Oct 2017 10:14:59 +0200
> Subject: [PATCH 1/3] Instrument function exit with __builtin_unreachable in
> C++
>
> gcc/c-family/ChangeLog:
>
> 2017-10-12 Martin Liska <mliska@suse.cz>
>
> PR middle-end/82404
> * c-opts.c (c_common_post_options): Set -Wreturn-type for C++
> FE.
> * c.opt: Set default value of warn_return_type.
>
> gcc/cp/ChangeLog:
>
> 2017-10-12 Martin Liska <mliska@suse.cz>
>
> PR middle-end/82404
> * constexpr.c (cxx_eval_builtin_function_call): Handle
> __builtin_unreachable call.
> * cp-gimplify.c (cp_ubsan_maybe_instrument_return): Rename to
> ...
> (cp_maybe_instrument_return): ... this.
> (cp_genericize): Call the function unconditionally.
>
> gcc/fortran/ChangeLog:
>
> 2017-10-12 Martin Liska <mliska@suse.cz>
>
> PR middle-end/82404
> * options.c (gfc_post_options): Set default value of
> -Wreturn-type to false.
> ---
> gcc/c-family/c-opts.c | 3 +++
> gcc/c-family/c.opt | 2 +-
> gcc/cp/constexpr.c | 8 +++++++-
> gcc/cp/cp-gimplify.c | 20 ++++++++++++++------
> gcc/fortran/options.c | 3 +++
> 5 files changed, 28 insertions(+), 8 deletions(-)
>
> diff --git a/gcc/c-family/c-opts.c b/gcc/c-family/c-opts.c
> index 6bd535532d3..682d7a83ec5 100644
> --- a/gcc/c-family/c-opts.c
> +++ b/gcc/c-family/c-opts.c
> @@ -978,6 +978,9 @@ c_common_post_options (const char **pfilename)
> flag_extern_tls_init = 1;
> }
>
> + if (warn_return_type == -1)
> + warn_return_type = c_dialect_cxx () ? 1 : 0;
Here you can simply
warn_return_type = c_dialect_cxx ();
no?
Marek