Re: [Qemu-devel] [PATCH v4 08/16] configure: Use -Wunused-const-variable

[Laurent Vivier]

Le 18/08/2018 à 21:01, Richard Henderson a écrit :
> For the linux-user syscall split, we have static const structs
> that must be matched up with a switch statement that uses them.
> By default, gcc will not warn for such a variable, but silently
> remove them.
> 
> For C++, such objects are sometimes declared for their constructor
> side effects.  Do not propagate this flag into QEM_CXXFLAGS.
> 
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  configure | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/configure b/configure
> index db97930314..86e6e18428 100755
> --- a/configure
> +++ b/configure
> @@ -105,7 +105,8 @@ update_cxxflags() {
>      for arg in $QEMU_CFLAGS; do
>          case $arg in
>              -Wstrict-prototypes|-Wmissing-prototypes|-Wnested-externs|\
> -            -Wold-style-declaration|-Wold-style-definition|-Wredundant-decls)
> +            
> -Wold-style-declaration|-Wold-style-definition|-Wredundant-decls|\
> +            -Wunused-const-variable)
>                  ;;
>              *)
>                  QEMU_CXXFLAGS=${QEMU_CXXFLAGS:+$QEMU_CXXFLAGS }$arg
> @@ -1780,6 +1781,7 @@ gcc_flags="-Wendif-labels -Wno-shift-negative-value 
> $gcc_flags"
>  gcc_flags="-Wno-initializer-overrides -Wexpansion-to-defined $gcc_flags"
>  gcc_flags="-Wno-string-plus-int $gcc_flags"
>  gcc_flags="-Wno-error=address-of-packed-member $gcc_flags"
> +gcc_flags="-Wunused-const-variable $gcc_flags"
>  # Note that we do not add -Werror to gcc_flags here, because that would
>  # enable it for all configure tests. If a configure test failed due
>  # to -Werror this would just silently disable some features,
> 

This breaks build of hw/misc/macio/gpio.o:

In file included from include/hw/misc/macio/macio.h:33,
                 from hw/misc/macio/gpio.c:29:
hw/misc/macio/pmu.h:129:21: error: 'pmu_data_len' defined but not used
[-Werror=unused-const-variable=]
 static const int8_t pmu_data_len[256][2] = {
                     ^~~~~~~~~~~~
In file included from include/hw/misc/macio/macio.h:33,
                 from hw/misc/macio/macio.c:33:
include/hw/misc/macio/pmu.h:129:21: error: 'pmu_data_len' defined but
not used [-Werror=unused-const-variable=]
 static const int8_t pmu_data_len[256][2] = {
                     ^~~~~~~~~~~~

This can be fixed by moving pmu_data_len array from pmu.h to pmu.c as it
is the only user.

Thanks,
Laurent