Re: [PATCH] meson: fix qxl module build

[Paolo Bonzini <pbonzini@redhat.com>]

On 04/09/20 10:12, Gerd Hoffmann wrote:
>   Hi,
> 
>>  if config_all_devices.has_key('CONFIG_QXL')
>>    qxl_ss = ss.source_set()
>> -  qxl_ss.add(when: 'CONFIG_QXL', if_true: files('qxl.c', 'qxl-logger.c', 'qxl-render.c'))
>> +  qxl_ss.add(files('qxl.c', 'qxl-logger.c', 'qxl-render.c'))
>>    hw_display_modules += {'qxl': qxl_ss}
>>  endif
>>  
>> -softmmu_ss.add(when: 'CONFIG_QXL', if_true: files('qxl.c', 'qxl-logger.c', 'qxl-render.c'))
> 
> Damn.  Turned out to not be that easy.  Modular builds work fine, but
> with non-modular builds I have the problem that qxl_ss is merged into
> softmmu_ss *unconditionally*.  So when building two targets, one with
> qxl enabled (i386 for example) and one without pci support (avr for
> example) I get missing symbols for pci+vga due to the attempt to link
> qxl into avr-softmmu.

You have found why it's got that "when:". :)

> Any hints how to solve that one?

I think this should be enough---fixing it in the common code, not with a
qxl-specific change:

diff --git a/meson.build b/meson.build
index 6ed3c37f46..88f2254f3b 100644
--- a/meson.build
+++ b/meson.build
@@ -923,7 +923,7 @@ softmmu_mods = []
 foreach d, list : modules
   foreach m, module_ss : list
     if enable_modules and targetos != 'windows'
-      module_ss = module_ss.apply(config_host, strict: false)
+      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)
       if d == 'block'

:-O

If you want to get rid of the "if config_all_devices.has_key(...)", you perhaps
could try doing something like

  module_srcs = module_ss.sources()
  if module_srcs.length() == 0
    continue
  endif
  sl = static_library(d + '-' + m, [genh, module_srcs],
                      dependencies: [modulecommon, module_ss.dependencies()], pic: true)

etc.  This would work also for the CONFIG_VIRTIO_GPU changes.

Paolo