Re: Cygwin GDB crashes from cvs - solib

[Christopher Faylor <cgf-use-the-mailinglist-please at sourceware dot org>]

[reply-to set]
On Mon, Apr 10, 2006 at 06:47:34PM +0100, Dave Korn wrote:
>On 10 April 2006 18:21, Daniel Jacobowitz wrote:
>>Currently win32-nat.c sets in_dynsym_resolve_code and open_symbol_file
>>to NULL.  The latter doesn't normally get called, but when it does, it
>>is called unconditionally; the former is called by "step".  Should
>>win32-nat provide dummy functions or should the call sites check?
>>Anyone have an opinion?
>
>Well, IIUIC, we have various target vectors of different kinds
>throughout gcc binutils and gdb, and in every case that I can bring to
>mind off the top of my head, there's no requirement that every single
>entry has to be initialised, and a NULL entry indicates 'target does
>not have capability'.
>
>So from that point of view, ISTM that no call site should blindly jump
>through a target vector pointer without first checking that it is
>non-NULL, unless it already 'knows' by some other means that the
>current target /has/ to have the capability in question (in which case
>if the pointer is NULL it's a programming bug because the information
>in the target vector must not be semantically self-consistent).
>
>IASTM that if we start requiring all function-pointers in target
>vectors to be filled out with a pointer to a dummy function if there is
>no real function for the target, we lose the ability to test if the
>target has the given capability, and it would, in time, lead to people
>being tempted to write really ugly code such as:-
>
>if (current_target_so_ops->open_symbol_file ==
>&dummy_open_symbol_file_stub) ...  assume we don't have the capability
>...  else ...  assume we do ...
>
>which wouldn't be a good thing IMO.
>
>However that's a generic POV on the general issue.  Cgf will probably
>have a relevant opinion about this particular problem since he's been
>paying some attention to the win32 native solib stuff lately and I
>would defer to his judgement on this one.

I don't think you really need my opinion on this.  The above reasoning
seems to me to be 100% correct.

Whether win32-nat.c should add these two functions (or any others that
may be missing) is really another problem entirely.

cgf