Re: [Xen-devel] [PATCH v3 00/25] chardev: Convert qemu_chr_write() to take a size_t argument

[Marc-André Lureau <marcandre.lureau@xxxxxxxxxx>]

Hi

On Wed, Feb 20, 2019 at 2:02 AM Philippe Mathieu-Daudé
<philmd@xxxxxxxxxx> wrote:
>
> Hi,
>
> This series convert the chardev::qemu_chr_write() to take unsigned
> length argument. To do so I went through all caller and checked if
> there are no negative value possible.


Changing signedness is problematic and can easily introduce bugs that
are easy to miss during review.

I agree with Cornelia about idiomatic use of int. Changing "int" for
"size_t" isn't systematically a clear win.

Even Google C++ style recommends to avoid unsigned types "(except for
representing bitfields or modular arithmetic). Do not use an unsigned
type merely to assert that a variable is non-negative."
https://google.github.io/styleguide/cppguide.html#Integer_Types - see rationale

Since Paolo you suggested the change, could you give some convincing
arguments that it's worth taking the plunge?

thanks

>
> I'm having headaches with the Xen backend, talking with Marc-André
> he suggested I ask help to the Xen maintainers.
>
> Since the series is becoming quite big, I splitted it:
> - part 1: convert qemu_chr_write()
> - part 2: convert IOReadHandler
>
> part 1 can be reviewed and merged without part 2.
>
> The git diffstat is not huge, but there are various chardev subsystems
> so many maintainers to ask for Ack.
>
> v2: https://lists.gnu.org/archive/html/qemu-devel/2018-10/msg02396.html
> v1: https://lists.gnu.org/archive/html/qemu-devel/2018-10/msg02200.html
>     (from Prasad J Pandit)
> Changes requested by Paolo:
> https://lists.gnu.org/archive/html/qemu-devel/2018-10/msg02294.html
>
> Please review,
>
> Phil.
>
> Philippe Mathieu-Daudé (25):
>   chardev: Simplify IOWatchPoll::fd_can_read as a GSourceFunc
>   chardev: Assert IOCanReadHandler can not be negative
>   chardev/wctablet: Use unsigned type to hold unsigned value
>   chardev: Let qemu_chr_be_can_write() return a size_t types
>   gdbstub: Use size_t for strlen() return value
>   gdbstub: Use size_t to hold GDBState::last_packet_len
>   gdbstub: Let put_buffer() use size_t
>   ui/gtk: Remove pointless cast
>   vhost-user: Express sizeof with size_t
>   usb-redir: Verify usbredirparser_write get called with positive count
>   xen: Let xencons_send() take a 'size' argument
>   xen: Let buffer_append() return the size consumed
>   RFC xen: Let buffer_append() return a size_t
>   virtio-serial: Let VirtIOSerialPortClass::have_data() use size_t
>   spapr-vty: Let vty_putchars() use size_t
>   tpm: Use size_t to hold sizes
>   net/filter-mirror: Use size_t
>   s390x/3270: Let insert_IAC_escape_char() use size_t
>   s390/ebcdic: Use size_t to iterate over arrays
>   s390x/sclp: Use a const variable to improve readability
>   s390x/sclp: Use size_t in process_mdb()
>   s390x/sclp: Let write_console_data() take a size_t
>   hw/ipmi: Assert outlen > outpos
>   chardev: Let qemu_chr_fe_write[_all] use size_t type argument
>   chardev: Let qemu_chr_write[_all] use size_t
>
>  chardev/baum.c                    |  6 +++---
>  chardev/char-fd.c                 |  6 +++---
>  chardev/char-fe.c                 |  4 ++--
>  chardev/char-io.c                 |  6 +++---
>  chardev/char-mux.c                |  3 ++-
>  chardev/char-pty.c                |  8 ++++----
>  chardev/char-socket.c             | 13 +++++++------
>  chardev/char-udp.c                |  8 ++++----
>  chardev/char-win.c                |  2 +-
>  chardev/char.c                    | 15 +++++++++------
>  chardev/msmouse.c                 |  4 ++--
>  chardev/spice.c                   |  2 +-
>  chardev/trace-events              |  2 +-
>  chardev/wctablet.c                |  9 +++++----
>  gdbstub.c                         |  8 ++++----
>  hw/bt/hci-csr.c                   |  2 +-
>  hw/char/sclpconsole-lm.c          | 12 +++++++-----
>  hw/char/spapr_vty.c               |  2 +-
>  hw/char/terminal3270.c            |  7 ++++---
>  hw/char/virtio-console.c          |  2 +-
>  hw/char/xen_console.c             | 24 +++++++++++++++---------
>  hw/ipmi/ipmi_bmc_extern.c         |  3 ++-
>  hw/tpm/tpm_emulator.c             |  7 ++++---
>  hw/usb/redirect.c                 |  6 +++++-
>  hw/virtio/vhost-user.c            | 14 ++++++++------
>  include/chardev/char-fd.h         |  2 +-
>  include/chardev/char-fe.h         |  4 ++--
>  include/chardev/char-io.h         |  2 +-
>  include/chardev/char.h            |  4 ++--
>  include/hw/ppc/spapr_vio.h        |  2 +-
>  include/hw/s390x/ebcdic.h         |  8 ++++----
>  include/hw/virtio/virtio-serial.h |  2 +-
>  include/sysemu/replay.h           |  2 +-
>  net/filter-mirror.c               |  2 +-
>  replay/replay-char.c              |  2 +-
>  stubs/replay.c                    |  2 +-
>  ui/console.c                      |  6 +++---
>  ui/gtk.c                          |  2 +-
>  38 files changed, 119 insertions(+), 96 deletions(-)
>
> --
> 2.20.1
>

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