Re: [Valgrind-developers] Semantics of ML_(fd_allowed) ?

[Nicholas N. <nj...@cs...>]

On Fri, 30 Sep 2005, Julian Seward wrote:

> I've been looking a little at ML_(fd_allowed), in syswrap-generic.c.
> This function decides which fds syscalls are allowed to create/use,
> so that V's own fds don't get trashed.
>
> This is a good thing; however I'm not sure I understand the logic.
>
> - the first conditional reads
>
>   if ( (fd < 0 || fd >= VG_(fd_hard_limit) || fd == VG_(clo_log_fd))
>        && VG_(showing_core_errors)() ) {
>      ... stuff ...
>      return False;
>   }
>
>  which seems to imply that some part of the decision rests on
>  what VG_(showing_core_errors)() produces, iow on what sounds
>  like a setting in the error-displaying options.  That seems a
>  little odd.

It does look odd.  Some of the subsequent "else if" cases cover some of 
these cases, but not all.  I think it should really be something like 
this:

   if (some conditions) {
      if (showing_core_erros && more specific conditions) {
         print error msg
      }
      return False;
   } else {
      return True;
   }

> - what does the "Bool soft" parameter mean?

There are two fd limits, the soft and hard limits.  I think the client can 
only access those below the soft limit, and Valgrind can access those 
below the hard limit?  Something like that.

Nick