Re: [PATCH] configure: Support modules for Windows

[LIU Zhiwei]

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_...@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.

This is passing a literal '0' which doesn't
make sense. Is this really needed ?

It will not be a literal '0'

What is the reason for the "dependencies" addition ?

I don't think the import library will include the symbols of glib.  And 
many modules need
link with glib. So I add the dependencies.

Can we not just use the existing shared_module() rules
we already have. It might be ok to just add dependencies
to the existing rule even for non-windows.

I think you are right. It is difficult for me to add all dependencies to 
modules.
I use a rough method that export all symbols in the executable.

I am not clear about the right way to support this feature. Look forward 
to you more advice.

Thanks,
Zhiwei

+           install_dir: qemu_moddir)
+  endforeach
+endif


Regards,
Daniel