Allow building 32-bit yabridge libraries

CHANGELOG.md

@@ -18,6 +18,11 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 - Added an environment variable to disable the watchdog timer. This allows the
   Wine process to run under a separate namespace. If you don't know that you
   need this, then you probably don't need this!
+- Added support for building 32-bit versions of the yabridge libraries, so you
+  can use both 32-bit and 64-bit Windows VST2 and VST3 plugins under 32-bit
+  Linux plugin hosts. This should not be necessary in any normal situation since
+  Desktop Linux has been 64-bit only for a while now, but it could be useful in
+  some very specific situations.
 
 ### Changed
 

README.md

@@ -753,6 +753,24 @@ This will produce four files called `yabridge-host-32.exe`,
 trying to load is 32-bit or 64-bit, and will run either the regular version or
 the `*-32.exe` variant accordingly.
 
+### 32-bit libraries
+
+It also possible to build 32-bit versions of yabridge's libraries, which would
+let you use both 32-bit and 64-bit Windows VST2 and VST3 plugins from a 32-bit
+Linux plugin host. This is mostly untested since 32-bit desktop Linux doesn't
+really exist anymore, but it should work! The build system will still assume
+you're compiling from a 64-bit system, so if you're compiling on an actual
+32-bit system you would need to comment out the 64-bit `yabridge-host` and
+`yabridge-group` binaries in `meson.build`:
+
+```shell
+meson setup --buildtype=release --cross-file=cross-wine.conf --unity=on --unity-size=1000 -Dwith-bitbridge=true -Dbuild.cpp_link_args='-m32' build
+ninja -C build
+```
+
+Like the above commands, you might need to tweak the unity size based on the
+amount of system memory available.
+
 ## Debugging
 
 Wine's error messages and warning are usually very helpful whenever a plugin

meson.build

@@ -145,12 +145,27 @@ endif
 # Statically link against Boost.Filesystem, otherwise it would become impossible
 # to distribute a prebuilt version of yabridge
 boost_dep = dependency('boost', version : '>=1.66', static : with_static_boost)
-boost_filesystem_dep = dependency(
-  'boost',
-  version : '>=1.66',
-  modules : ['filesystem'],
-  static : with_static_boost,
-)
+
+# HACK: I couldn't get Meson's Boost dependency detection to work with `-m32`,
+#       because no matter what settings I use in machine/cross files it will
+#       keep rejecting the 32-bit libraries when the host system is 64-bit.
+#       Since cross-compiling 32-bit native libraries is not really a supported
+#       use case anyways we'll just brute force it for the time being.
+if get_option('build.cpp_args').contains('-m32')
+  if with_static_boost
+    boost_filesystem_dep = declare_dependency(link_args : '-staticboost_filesystem')
+  else
+    boost_filesystem_dep = declare_dependency(link_args : '-lboost_filesystem')
+  endif
+else
+  boost_filesystem_dep = dependency(
+    'boost',
+    version : '>=1.66',
+    modules : ['filesystem'],
+    static : with_static_boost,
+  )
+endif
+
 # TODO: Meson doesn't have a way to define version ranges, does it? Like
 #       `^>=5.2.0`, `>=5.2.0 && <6.0.0` or `5.2.*`.
 bitsery_dep = dependency('bitsery', version : '>=5.2.0', fallback : ['bitsery', 'bitsery_dep'])