Re: [Xen-devel] [PATCH v2 0/2] misc: Replace zero-length arrays with flexible array member

[John Snow <jsnow@xxxxxxxxxx>]

On 3/4/20 10:38 AM, Philippe Mathieu-Daudé wrote:
> v2:
> - do not modify qed.h (structure with single member)
> - based on hw/scsi/spapr_vscsi fix series:
>   https://mid.mail-archive.com/20200304153311.22959-1-philmd@xxxxxxxxxx
> 
> This is a tree-wide cleanup inspired by a Linux kernel commit
> (from Gustavo A. R. Silva).
> 
> --v-- description start --v--
> 
>   The current codebase makes use of the zero-length array language
>   extension to the C90 standard, but the preferred mechanism to
>   declare variable-length types such as these ones is a flexible
>   array member [1], introduced in C99:
> 
>   struct foo {
>       int stuff;
>       struct boo array[];
>   };
> 
>   By making use of the mechanism above, we will get a compiler
>   warning in case the flexible array does not occur last in the
>   structure, which will help us prevent some kind of undefined
>   behavior bugs from being unadvertenly introduced [2] to the
>   Linux codebase from now on.
> 
> --^-- description end --^--
> 
> Do the similar housekeeping in the QEMU codebase (which uses
> C99 since commit 7be41675f7cb).
> 
> The first patch is done with the help of a coccinelle semantic
> patch. However Coccinelle does not recognize:
> 
>   struct foo {
>       int stuff;
>       struct boo array[];
>   } QEMU_PACKED;
> 
> but does recognize:
> 
>   struct QEMU_PACKED foo {
>       int stuff;
>       struct boo array[];
>   };
> 
> I'm not sure why, neither it is worth refactoring all QEMU
> structures to use the attributes before the structure name,
> so I did the 2nd patch manually.
> 
> Anyway this is annoying, because many structures are not handled
> by coccinelle. Maybe this needs to be reported to upstream
> coccinelle?
> 
> I used spatch 1.0.8 with:
> 
>   -I include --include-headers \
>   --macro-file scripts/cocci-macro-file.h \
>   --keep-comments --indent 4
> 
> Regards,
> 
> Phil.
> 
> Based-on: <20200304153311.22959-1-philmd@xxxxxxxxxx>
> Supersedes: <20200304005105.27454-1-philmd@xxxxxxxxxx>
> 
> Philippe Mathieu-Daudé (2):
>   misc: Replace zero-length arrays with flexible array member
>     (automatic)
>   misc: Replace zero-length arrays with flexible array member (manual)
> 
>  docs/interop/vhost-user.rst           |  4 ++--
>  bsd-user/qemu.h                       |  2 +-
>  contrib/libvhost-user/libvhost-user.h |  2 +-
>  hw/m68k/bootinfo.h                    |  2 +-
>  hw/scsi/srp.h                         |  6 +++---
>  hw/xen/xen_pt.h                       |  2 +-
>  include/hw/acpi/acpi-defs.h           | 16 ++++++++--------
>  include/hw/arm/smmu-common.h          |  2 +-
>  include/hw/boards.h                   |  2 +-
>  include/hw/i386/intel_iommu.h         |  3 ++-
>  include/hw/s390x/event-facility.h     |  2 +-
>  include/hw/s390x/sclp.h               |  8 ++++----
>  include/hw/virtio/virtio-iommu.h      |  2 +-
>  include/sysemu/cryptodev.h            |  2 +-
>  include/tcg/tcg.h                     |  2 +-
>  pc-bios/s390-ccw/bootmap.h            |  2 +-
>  pc-bios/s390-ccw/sclp.h               |  2 +-
>  tests/qtest/libqos/ahci.h             |  2 +-
>  block/linux-aio.c                     |  2 +-
>  block/vmdk.c                          |  2 +-
>  hw/acpi/nvdimm.c                      |  6 +++---
>  hw/char/sclpconsole-lm.c              |  2 +-
>  hw/char/sclpconsole.c                 |  2 +-
>  hw/dma/soc_dma.c                      |  2 +-
>  hw/i386/x86.c                         |  2 +-
>  hw/misc/omap_l4.c                     |  2 +-
>  hw/nvram/eeprom93xx.c                 |  2 +-
>  hw/rdma/vmw/pvrdma_qp_ops.c           |  4 ++--
>  hw/s390x/virtio-ccw.c                 |  2 +-
>  hw/usb/dev-network.c                  |  2 +-
>  hw/usb/dev-smartcard-reader.c         |  4 ++--
>  hw/virtio/virtio.c                    |  4 ++--
>  net/queue.c                           |  2 +-
>  target/s390x/ioinst.c                 |  2 +-
>  34 files changed, 53 insertions(+), 52 deletions(-)
> 

I'll admit I did not manually verify ALL of this, but instead trust that:

1. The conversion is correct, and this is a desirable change to make.
2. Sample conversions I looked at appear correct.
3. It builds.
4. It passes tests.

So:

Acked-by: John Snow <jsnow@xxxxxxxxxx>


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