On 01/19/18 20:48, Eric Blake wrote: > On 01/19/2018 01:18 PM, Laszlo Ersek wrote: >> On 01/19/18 17:25, Marc-André Lureau wrote: >>> Python GDB support may use Python 2 or 3. >>> >>> Inferior.read_memory() may return a 'buffer' with Python 2 or a >>> 'memoryview' with Python 3 (see also >>> https://sourceware.org/gdb/onlinedocs/gdb/Inferiors-In-Python.html) >>> >>> The elf.add_vmcoreinfo_note() method expects a "bytes" object. Wrap >>> the returned memory with bytes(), which works with both 'memoryview' >>> and 'buffer'. >>> > > If I understand it, the issue stems from the fact that vmcoreinfo is a > bytes buffer under python2, but a memoryview under python3. Let's > compare the patches: > > The V1 patch: > https://lists.gnu.org/archive/html/qemu-devel/2018-01/msg04010.html > >> >> if vmcoreinfo: >> - self.elf.add_vmcoreinfo_note(vmcoreinfo.tobytes()) >> + # Python 2.7 returns a buffer >> + vmciview = memoryview(vmcoreinfo) >> + self.elf.add_vmcoreinfo_note(vmciview.tobytes()) > > did an unconditional memoryview(vmcoreinfo) followed by a .tobytes() > call. Under python 2.7, vmcoreinfo is converted from a buffer to a > memoryview, then back to bytes; under python 3, memoryview(vmcoreinfo) > is a no-op (since it is already a memory view), then that is converted > to bytes; the double conversion was necessary because bytes.tobytes() > doesn't exist. But python 2.6 doesn't have the memoryview conversion, > so we've excluded older python users. > > Now looking at the V2 patch: > > >>> @@ -564,7 +564,7 @@ shape and this command should mostly work.""" >>> >>> vmcoreinfo = self.phys_memory_read(addr, size) >>> if vmcoreinfo: >>> - self.elf.add_vmcoreinfo_note(vmcoreinfo.tobytes()) >>> + self.elf.add_vmcoreinfo_note(bytes(vmcoreinfo)) > > Under python2, and bytes(buffer) is still bytes; under python3, > vmcoreinfo is a memoryview but bytes(buffer) is equivalent to > buffer.to_bytes(). We've avoided the intermediate conversion through > memoryview, and thus work regardless of python version.
Heh, "semantics" :) > >> Ugh, can you please point me to the v1->v2 difference? > > Hope that helped (and hope I got it right, I'm learning as well from > this thread). > It sure helped a lot, thank you very much! In fact, you've done all the review work, so technically, "R-b: Laszlo" would be misappropriation. Can you give your R-b? I'll manage an "I agree" statement: Acked-by: Laszlo Ersek <ler...@redhat.com> Thanks! Laszlo
