Re: [PATCH] configure: Support modules for Windows

[Daniel P . Berrangé]

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 ?


Regards,
Daniel
-- 
|: https://berrange.com      -o-    https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org         -o-            https://fstop138.berrange.com :|
|: https://entangle-photo.org    -o-    https://www.instagram.com/dberrange :|