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Re: [PATCH v2 3/3] Replace home-grown linked-lists in FreeBSD's native target with STL lists.


On 2017-08-09 21:15, John Baldwin wrote:
On Wednesday, August 09, 2017 08:16:29 PM Simon Marchi wrote:
On 2017-08-09 19:47, John Baldwin wrote:
> diff --git a/gdb/fbsd-nat.c b/gdb/fbsd-nat.c
> index 721e72b85c..c89343a24f 100644
> --- a/gdb/fbsd-nat.c
> +++ b/gdb/fbsd-nat.c
> @@ -41,6 +41,8 @@
>  #include "elf-bfd.h"
>  #include "fbsd-nat.h"
>
> +#include <list>
> +
>  /* Return the name of a file that can be opened to get the symbols for
>     the child process identified by PID.  */
>
> @@ -712,13 +714,7 @@ fbsd_update_thread_list (struct target_ops *ops)
>    sake.  FreeBSD versions newer than 9.1 contain both fixes.
>  */
>
> -struct fbsd_fork_info
> -{
> -  struct fbsd_fork_info *next;
> -  ptid_t ptid;
> -};
> -
> -static struct fbsd_fork_info *fbsd_pending_children;
> +static std::list<ptid_t> fbsd_pending_children;

Can't this be a forward_list as well?

Not trivially. fbsd_is_child_pending has to walk the list looking for a
specific PID and remove that specific list entry (not always the first
entry).  Right now this is using the following loop:

   for (auto it = fbsd_pending_children.begin ();
       it != fbsd_pending_children.end (); it++)
     if (it->pid () == pid)
       {
         ptid_t ptid = *it;
         fbsd_pending_children.erase (it);
         return ptid;
       }
   return null_ptid;

I'm not sure if it's legal to do something like this for a forward_list:

   for (auto it = fbsd_pending_children.before_begin ();
        it + 1 != fbsd_pending_children.end (); it++)
    if ((it + 1)->pid () == pid)
       {
         ptid_t ptid = *(it + 1);
         fbsd_pending_childern.erase_after (it);
         return ptid;
       }
   return null_ptid;

Even if it is legal, I'm not sure it is more readable. These lists should
generally be quite small, so I think readability is more important than
optimization in this case.

Ah, ok. I thought it could be done trivially, but I can't easily build-test on FreeBSD right now.

I agree with you.

Simon


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