Re: [PATCH] configure: Support modules for Windows

[LIU Zhiwei <zhiwei_liu@c-sky.com>]

On 2021/11/5 下午8:22, Daniel P. Berrangé wrote:
> On Fri, Nov 05, 2021 at 08:14:29PM +0800, LIU Zhiwei wrote:
>> On 2021/11/5 下午5:30, Daniel P. Berrangé wrote:
>>> On Fri, Nov 05, 2021 at 11:20:02AM +0800, LIU Zhiwei wrote:
>>>
>>> Generally we expect a commit message describing what is being solved
>>> and any reasons for the approach taken.
>> This patch relaxes all constraints on modules for Windows.  It firstly
>> exports  all symbols of the
>> target executable to an import library. Then  all modules link with the
>> import library .
>>
>>>> Signed-off-by: LIU Zhiwei <zhiwei_liu@c-sky.com>
>>>> ---
>>>>    configure   |  7 +------
>>>>    meson.build | 34 ++++++++++++++++++++++++----------
>>>>    2 files changed, 25 insertions(+), 16 deletions(-)
>>>>
>>>> diff --git a/configure b/configure
>>>> index 33682cb971..6280e412a9 100755
>>>> --- a/configure
>>>> +++ b/configure
>>>> @@ -1422,7 +1422,7 @@ cat << EOF
>>>>      bsd-user        all BSD usermode emulation targets
>>>>      guest-agent     build the QEMU Guest Agent
>>>>      pie             Position Independent Executables
>>>> -  modules         modules support (non-Windows)
>>>> +  modules         modules support
>>>>      module-upgrades try to load modules from alternate paths for upgrades
>>>>      debug-tcg       TCG debugging (default is disabled)
>>>>      debug-info      debugging information
>>>> @@ -1698,11 +1698,6 @@ else
>>>>      QEMU_CFLAGS="$QEMU_CFLAGS -Wno-missing-braces"
>>>>    fi
>>>> -# Our module code doesn't support Windows
>>>> -if test "$modules" = "yes" && test "$mingw32" = "yes" ; then
>>>> -  error_exit "Modules are not available for Windows"
>>>> -fi
>>>> -
>>>>    # module_upgrades is only reasonable if modules are enabled
>>>>    if test "$modules" = "no" && test "$module_upgrades" = "yes" ; then
>>>>      error_exit "Can't enable module-upgrades as Modules are not enabled"
>>>> diff --git a/meson.build b/meson.build
>>>> index 47df10afc2..26195cb24f 100644
>>>> --- a/meson.build
>>>> +++ b/meson.build
>>>> @@ -2625,7 +2625,7 @@ block_mods = []
>>>>    softmmu_mods = []
>>>>    foreach d, list : modules
>>>>      foreach m, module_ss : list
>>>> -    if enable_modules and targetos != 'windows'
>>>> +    if enable_modules
>>>>          module_ss = module_ss.apply(config_all, strict: false)
>>>>          sl = static_library(d + '-' + m, [genh, module_ss.sources()],
>>>>                              dependencies: [modulecommon, module_ss.dependencies()], pic: true)
>>>> @@ -2658,7 +2658,7 @@ endforeach
>>>>    foreach d, list : target_modules
>>>>      foreach m, module_ss : list
>>>> -    if enable_modules and targetos != 'windows'
>>>> +    if enable_modules
>>>>          foreach target : target_dirs
>>>>            if target.endswith('-softmmu')
>>>>              config_target = config_target_mak[target]
>>>> @@ -2800,14 +2800,15 @@ common_ss.add(hwcore)
>>>>    ###########
>>>>    # Targets #
>>>>    ###########
>>>> -
>>>> -foreach m : block_mods + softmmu_mods
>>>> -  shared_module(m.name(),
>>>> -                name_prefix: '',
>>>> -                link_whole: m,
>>>> -                install: true,
>>>> -                install_dir: qemu_moddir)
>>>> -endforeach
>>>> +if targetos != 'windows'
>>>> +  foreach m : block_mods + softmmu_mods
>>>> +    shared_module(m.name(),
>>>> +                  name_prefix: '',
>>>> +                  link_whole: m,
>>>> +                  install: true,
>>>> +                  install_dir: qemu_moddir)
>>>> +  endforeach
>>>> +endif
>>>>    softmmu_ss.add(authz, blockdev, chardev, crypto, io, qmp)
>>>>    common_ss.add(qom, qemuutil)
>>>> @@ -2826,6 +2827,7 @@ common_all = static_library('common',
>>>>    feature_to_c = find_program('scripts/feature_to_c.sh')
>>>>    emulators = {}
>>>> +emulator = 0
>>>>    foreach target : target_dirs
>>>>      config_target = config_target_mak[target]
>>>>      target_name = config_target['TARGET_NAME']
>>>> @@ -2966,6 +2968,7 @@ foreach target : target_dirs
>>>>                   link_language: link_language,
>>>>                   link_depends: [block_syms, qemu_syms] + exe.get('link_depends', []),
>>>>                   link_args: link_args,
>>>> +               implib: true,
>>>>                   win_subsystem: exe['win_subsystem'])
>>>>        if targetos == 'darwin'
>>>> @@ -3023,6 +3026,17 @@ foreach target : target_dirs
>>>>        endif
>>>>      endforeach
>>>>    endforeach
>>>> +if (targetos == 'windows')
>>>> +  foreach m : block_mods + softmmu_mods
>>>> +    shared_module(m.name(),
>>>> +	    name_prefix: '',
>>>> +	    link_whole: m,
>>>> +	    install: true,
>>>> +	    dependencies: glib,
>>>> +	    link_with: emulator,
>>> AFAIK from the docs meson wants "link_with" to be a list of
>>> libraries.
>> The emulator is an import library.
>>
>> There has been an executable variable named emulator in origin meson.build.
>> An implib keyword args has been  added in this patch when the executable
>> generates.
>> And I declare it to the out-most level  to make it visible for modules after
>> the build of targets.
> Oh, so the "emulator" variable is already present in the loop body
> from existing meson rules.
>
> This still feels odd though - QEMU has 30+ emulator binaries it
> can build. This code is linking modules to the implib of whichever
> happens to be the last emulator binary built.
>
> Does this really let the modules work against any of the emulator
> binaries  at runtime ?

Think about the Linux build. There don't exist different modules for 
different emulator binaries.
I guess it doesn't have much connection with the target.

Once again, may be it is not a right way. Hope to get for your guidance 
and help.

Thanks,
Zhiwei

>
>
> Regards,
> Daniel