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RE: [RFA] gdbserver/win32-low.c: Check Read/WriteProcessMemory return value (followup to [RFA] windows-nat.c: Handle ERROR_PARTIAL_COPY in windows_xfer_memory function)
- From: "Pierre Muller" <pierre dot muller at ics-cnrs dot unistra dot fr>
- To: "'Pedro Alves'" <palves at redhat dot com>
- Cc: <gdb-patches at sourceware dot org>
- Date: Mon, 2 Sep 2013 16:00:53 +0200
- Subject: RE: [RFA] gdbserver/win32-low.c: Check Read/WriteProcessMemory return value (followup to [RFA] windows-nat.c: Handle ERROR_PARTIAL_COPY in windows_xfer_memory function)
- Authentication-results: sourceware.org; auth=none
- References: <5223bb46 dot c6c0420a dot 5a41 dot 008dSMTPIN_ADDED_BROKEN at mx dot google dot com> <52248978 dot 90500 at redhat dot com> <000301cea7dd$17bc4af0$4734e0d0$ at muller@ics-cnrs.unistra.fr> <52249053 dot 6050103 at redhat dot com> <522494dc dot 297a420a dot 6ab0 dot 6047SMTPIN_ADDED_BROKEN at mx dot google dot com> <522497AF dot 8080800 at redhat dot com>
> > What about this patch,
> > it still does not allow to really return the number of bytes read or
> > written,
> > but at least it checks correctly if the API calls succeeded.
>
> No, as long as the read_memory/write_memory interfaces do not
> support partial transfers, we should only return true if the
> all of LEN was transferred. Otherwise, things like:
>
> static int
> gdb_read_memory (CORE_ADDR memaddr, unsigned char *myaddr, int len)
> {
> ...
> {
> res = read_inferior_memory (memaddr, myaddr, len);
> done_accessing_memory ();
>
> return res == 0 ? len : -1;
> }
> }
>
> will behave incorrectly in the ERROR_PARTIAL_COPY scenario...
This is still done in win32_{read/write}_inferior_memory which are the two
only callers of the static child_xfer_memory function in win32-low.c
Thus the aim was to narrow the behavior gap between
windows-nat.c windows_xfer_memory function
and the win32-low.c child_xfer_memory function,
without (for now) changing anything to the beghavior of gdbserver,
as guaranteed by the
static int
win32_write_inferior_memory (CORE_ADDR memaddr, const unsigned char *myaddr,
int len)
{
return child_xfer_memory (memaddr, (char *) myaddr, len, 1, 0) != len;
}
code...
The only thing I changed is that child_xfer_memory returns the correct
amount of read/written memory or -1 if an error, other than
ERRO_PARTIAL_COPY, occurred.
Thus I think that your answer is missing the intermediate
win32_{read/write}_inferior_memory level.
Pierre Muller