Re: [Qemu-devel] [PATCH 3/3] maint: Fix macros with broken 'do/while(0); ' usage

[Cornelia Huck <cohuck@redhat.com>]

On Thu, 30 Nov 2017 07:41:59 -0600
Eric Blake <eblake@redhat.com> wrote:

> The point of writing a macro embedded in a 'do { ... } while (0)'
> loop is so that the macro can be used as a drop-in statement with
> the caller supplying the trailing ';'.  Although our coding style
> frowns on brace-less 'if':
>   if (cond)
>     statement;
>   else
>     something else;
> the use of do/while (0) in a macro is absolutely essential for the
> purpose of avoiding a syntax error on the 'else' - but it only works
> if there is no trailing ';' in the macro (as the ';' in the code
> calling the macro would then be a second statement and cause the
> 'else' to not pair to the 'if').
> 
> Many of the places touched in this code are examples of the ugly
> bit-rotting debug print statements; cleaning those up is left as
> a bite-sized task for another day.
> 
> Found mechanically via: $ git grep -B1 'while (0);' | grep -A1 \\\\
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>  tests/acpi-utils.h         | 8 ++++----
>  ui/sdl_zoom_template.h     | 8 ++++----
>  audio/paaudio.c            | 4 ++--
>  hw/adc/stm32f2xx_adc.c     | 2 +-
>  hw/block/m25p80.c          | 2 +-
>  hw/char/cadence_uart.c     | 2 +-
>  hw/char/stm32f2xx_usart.c  | 2 +-
>  hw/display/cg3.c           | 2 +-
>  hw/display/dpcd.c          | 2 +-
>  hw/display/xlnx_dp.c       | 2 +-
>  hw/dma/pl330.c             | 2 +-
>  hw/dma/xlnx-zynq-devcfg.c  | 2 +-
>  hw/dma/xlnx_dpdma.c        | 2 +-
>  hw/i2c/i2c-ddc.c           | 2 +-
>  hw/misc/auxbus.c           | 2 +-
>  hw/misc/macio/mac_dbdma.c  | 4 ++--
>  hw/misc/mmio_interface.c   | 2 +-
>  hw/misc/stm32f2xx_syscfg.c | 2 +-
>  hw/misc/zynq_slcr.c        | 2 +-
>  hw/net/cadence_gem.c       | 2 +-
>  hw/ssi/mss-spi.c           | 2 +-
>  hw/ssi/stm32f2xx_spi.c     | 2 +-
>  hw/ssi/xilinx_spi.c        | 2 +-
>  hw/ssi/xilinx_spips.c      | 2 +-
>  hw/timer/a9gtimer.c        | 2 +-
>  hw/timer/cadence_ttc.c     | 2 +-
>  hw/timer/mss-timer.c       | 2 +-
>  hw/timer/stm32f2xx_timer.c | 2 +-
>  hw/tpm/tpm_passthrough.c   | 2 +-
>  hw/tpm/tpm_tis.c           | 2 +-
>  migration/rdma.c           | 2 +-
>  target/arm/translate-a64.c | 2 +-
>  target/s390x/kvm.c         | 2 +-
>  tests/tcg/test-mmap.c      | 2 +-
>  34 files changed, 42 insertions(+), 42 deletions(-)

> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> index b03f583032..06d06010a4 100644
> --- a/target/s390x/kvm.c
> +++ b/target/s390x/kvm.c
> @@ -58,7 +58,7 @@
>      if (DEBUG_KVM) {                          \
>          fprintf(stderr, fmt, ## __VA_ARGS__); \
>      }                                         \
> -} while (0);
> +} while (0)
> 
>  #define kvm_vm_check_mem_attr(s, attr) \
>      kvm_vm_check_attr(s, KVM_S390_VM_MEM_CTRL, attr)

Acked-by: Cornelia Huck <cohuck@redhat.com>