Re: [PATCH 1/5] Poison non-POD memset & non-trivially-copyable memcpy/memmove

[Simon Marchi <simon.marchi@polymtl.ca>]

On 2017-04-12 22:27, Pedro Alves wrote:
> This patch catches invalid initialization of non-POD types with
> memset, at compile time.
> 
> This is what I used to catch the problems fixed by the rest of the
> series:
> 
>   $ make -k 2>&1 | grep "deleted function"
>   src/gdb/breakpoint.c:951:53: error: use of deleted function ‘void*
> memset(T*, int, size_t) [with T = bp_location;
> <template-parameter-1-2> = void; size_t = long unsigned int]’
>   src/gdb/breakpoint.c:7325:32: error: use of deleted function ‘void*
> memset(T*, int, size_t) [with T = bp_location;
> <template-parameter-1-2> = void; size_t = long unsigned int]’
>   src/gdb/btrace.c:1153:42: error: use of deleted function ‘void*
> memset(T*, int, size_t) [with T = btrace_insn;
> <template-parameter-1-2> = void; size_t = long unsigned int]’
> 
> I'll move this to the end of the series before pushing (if agreed).
> 
> (I've posted another series recently that adds some of the same traits
> bits to common/traits.h.  They're really useful.)

That's really nice.  I'm actually surprised we didn't get random crashes 
because of that yet!

> diff --git a/gdb/common/poison.h b/gdb/common/poison.h
> new file mode 100644
> index 0000000..57a1733
> --- /dev/null
> +++ b/gdb/common/poison.h
> @@ -0,0 +1,83 @@
> +/* Poison symbols at compile time.
> +
> +   Copyright (C) 2017 Free Software Foundation, Inc.
> +
> +   This file is part of GDB.
> +
> +   This program is free software; you can redistribute it and/or 
> modify
> +   it under the terms of the GNU General Public License as published 
> by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see 
> <http://www.gnu.org/licenses/>.  */
> +
> +#ifndef COMMON_POISON_H
> +#define COMMON_POISON_H
> +
> +#include "traits.h"
> +
> +/* Poison memset of non-POD types.  The idea is catching invalid
> +   initialization of non-POD structs that is easy to be introduced as
> +   side effect of refactoring.  For example, say this:
> +
> + struct S { VEC(foo_s) *m_data; };
> +
> +is converted to this at some point:
> +
> + struct S {
> +   S() { m_data.reserve (10); }
> +   std::vector<foo> m_data;
> + };

Here it says struct S ...

> +
> +and old code was initializing B objects like this:
> +
> + struct B b;
> + memset (&b, 0, sizeof (B)); // whoops, now wipes vector.

... and here struct B?

Simon