RE: [RFA] windows-nat.c: Handle ERROR_PARTIAL_COPY in windows_xfer_memory function

["Pierre Muller" <pierre dot muller at ics-cnrs dot unistra dot fr>]

> -----Message d'origine-----
> De : gdb-patches-owner@sourceware.org [mailto:gdb-patches-
> owner@sourceware.org] De la part de Pedro Alves
> Envoyé : lundi 2 septembre 2013 14:50
> À : Pierre Muller
> Cc : gdb-patches@sourceware.org
> Objet : Re: [RFA] windows-nat.c: Handle ERROR_PARTIAL_COPY in
> windows_xfer_memory function
> 
> On 09/01/2013 11:10 PM, Pierre Muller wrote:
> > This is the patch that Pedro suggested I send
> > after his commit to remove deprecated_xfer_memory
> > in windows-nat.c.
> 
> Thanks.
> 
> >
> >   Pedro suggested that I submit this patch separately
> > (which I do here)... and with a gdbserver counterpart,
> > which I don't...
> >
> >   I tried, but finally realized that given the
> > read_memory / write_memory functions type defined
> > in target.h target_ops structure,
> > there is no way of passing information of partial
> > copy and of the length of this partial copy.
> > Indeed, the comments state that the return value is either 0 for success
> > or errno...
> >
> > This is not compatible with returning information that only part of the
> > request length
> > was read/written.
> 
> Well, we could just change that interface to make it possible...
> 
> The thing I don't like with doing this only on the native
> side, is that we're trying to get to a point where we
> can share the target backends between GDB and gdbserver:

  Well, when you look at the code inside child_xfer_memory,
you can notice that the return value of ReadProcessMemory or
WriteProcessMemory
is discarded, which means that it does behave more or less like the
new windows-nat.c code (at least in case of ERROR_PARTIAL_COPY)
for other errors, it might also return garbage...
anyhow, the calling code compares the returned value to the requested length
(LEN value)
so that the risk of generating a successful read_memory despite a failure
of ReadProcessMemory function is small... (the uninitialized variable done
would need to return the value LEN..)
It could of course still happen theoretically...

 
> <https://sourceware.org/gdb/wiki/LocalRemoteFeatureParity>.
> 
> Doing such a change on the GDB side only just means we're
> pushing the feature-parity goal for the Windows port
> further away...
> 
> > 2013-09-01  Pierre Muller  <muller@sourceware.org>
> >
> ...
> > 	Handle ERROR_PARTIAL_COPY error code.
> ...
> 
> This part is OK too.  (Please commit it separately from the
> plongest fix.)

Thanks for the approval,
patch committed,

Pierre Muller