Re: [PATCH] Specialize std::hash for ptid_t

[Vaseeharan Vinayagamoorthy <Vaseeharan.Vinayagamoorthy@arm.com>]

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Hello,


I think that after this patch is when I am seeing these errors when building cross toolchains, for arm-none-eabi and aarch64-none-elf, using gcc 4.8.

The errors are:


In file included from /…/src/binutils-gdb--gdb/gdbsupport/common-defs.h:206:0,


                 from /…/src/binutils-gdb--gdb/gdbsupport/common-exceptions.cc:20:


/…/src/binutils-gdb--gdb/gdbsupport/ptid.h:161:13: error: specialization of ‘template<class _Tp> struct std::hash’ in different namespace [-fpermissive]


 struct std::hash<ptid_t>


             ^



Kind regards,
Vasee


________________________________
From: Gdb-patches <gdb-patches-bounces+vvinayag=arm.com@sourceware.org> on behalf of Simon Marchi via Gdb-patches <gdb-patches@sourceware.org>
Sent: 11 September 2023 18:14
To: Tom Tromey <tromey@adacore.com>
Cc: gdb-patches@sourceware.org <gdb-patches@sourceware.org>
Subject: Re: [PATCH] Specialize std::hash for ptid_t

On 9/11/23 12:35, Tom Tromey wrote:
>>>>>> "Simon" == Simon Marchi <simon.marchi@polymtl.ca> writes:
>
> Simon> When searching on that topic, I found some sources advising against
> Simon> opening namespace std, like this one:
> ...
>
> Sounds good, here's v2.
>
> Tom
>
> commit 1d5a09c85bf97846438246397aaf4aae360c3783
> Author: Tom Tromey <tromey@adacore.com>
> Date:   Mon Sep 11 08:45:37 2023 -0600
>
>     Specialize std::hash for ptid_t
>
>     This changes hash_ptid to instead be a specialization of std::hash.
>     This makes it a little easier to use with standard containers.
>
> diff --git a/gdb/inferior.h b/gdb/inferior.h
> index 04672582984..29c90d15efa 100644
> --- a/gdb/inferior.h
> +++ b/gdb/inferior.h
> @@ -462,7 +462,7 @@ class inferior : public refcounted_object,
>
>    /* A map of ptid_t to thread_info*, for average O(1) ptid_t lookup.
>       Exited threads do not appear in the map.  */
> -  std::unordered_map<ptid_t, thread_info *, hash_ptid> ptid_thread_map;
> +  std::unordered_map<ptid_t, thread_info *> ptid_thread_map;
>
>    /* Returns a range adapter covering the inferior's threads,
>       including exited threads.  Used like this:
> diff --git a/gdb/regcache.c b/gdb/regcache.c
> index 9b71931bb0b..91b20b7a2a2 100644
> --- a/gdb/regcache.c
> +++ b/gdb/regcache.c
> @@ -329,7 +329,7 @@ reg_buffer::assert_regnum (int regnum) const
>     regcaches, associated to different gdbarches).  */
>
>  using ptid_regcache_map
> -  = std::unordered_multimap<ptid_t, regcache_up, hash_ptid>;
> +  = std::unordered_multimap<ptid_t, regcache_up>;
>
>  /* Type holding regcaches for a given pid.  */
>
> diff --git a/gdbsupport/ptid.h b/gdbsupport/ptid.h
> index aa296b83181..f8644d47633 100644
> --- a/gdbsupport/ptid.h
> +++ b/gdbsupport/ptid.h
> @@ -157,9 +157,8 @@ class ptid_t
>    tid_type m_tid;
>  };
>
> -/* Functor to hash a ptid.  */
> -
> -struct hash_ptid
> +template<>
> +struct std::hash<ptid_t>
>  {
>    size_t operator() (const ptid_t &ptid) const
>    {

LGTM, thanks.

Approved-By: Simon Marchi <simon.marchi@efficios.com>

Simon