It is probably best to make the code loop as long as "bytes_reads > 0" and we
haven't read "num_bytes" yet. The darwin kernel has a INT32_MAX read size which
gets set to MAX_READ_SIZE, but we need to do that because if you try to read
more than that it reads nothing. So MAX_READ_SIZE is more for the case where
the read will outright fail if given a byte size that is too large. Feel free
to submit a patch that can keep calling pread correctly in a loop as long as
bytes_read > 0.
Greg
> On Oct 17, 2016, at 12:20 PM, Eugene Birukov via lldb-dev
> <lldb-dev@lists.llvm.org> wrote:
>
> Hello,
>
> I am using LLDB 3.9 on Linux Ubuntu. I am loading a 5GiB core which is
> located on Windows file share mounted on Linux via mount.cifs. I see that we
> successfully allocated memory and are trying to fill it in one read.
> Unfortunately pread returns 2GiB and we never check for short read here.
>
> I think we could combine this code with previous block "#if defined
> (MAX_READ_SIZE)" if we simply check for short read here (bytes_read too
> small) and loop until all the buffer is filled.
>
> Thanks,
> Eugene
>
> #ifndef _WIN32
> int fd = GetDescriptor();
> if (fd != kInvalidDescriptor)
> {
> ssize_t bytes_read = -1;
> do
> {
> bytes_read = ::pread (fd, buf, num_bytes, offset);
> } while (bytes_read < 0 && errno == EINTR);
>
> if (bytes_read < 0)
> {
> num_bytes = 0;
> error.SetErrorToErrno();
> }
> else
> {
> offset += bytes_read;
> num_bytes = bytes_read;
> }
> }
>
> Sent from Outlook
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> lldb-dev@lists.llvm.org
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