Fix ABI compatibility with 32-bit VST3 plugins #80

This would cause 32-bit VST3 plugins to crash in mysterious ways. What
ended up being the issue is that the plugins expected doubles to be
8-byte aligned in structs, while GCC doesn't do that by default in x86
code for legacy ABI compatibility reasons. Figuring out what exactly was
the issue took months, but luckily the fix was to just add an
`-malign-double`!

CHANGELOG.md

@@ -8,6 +8,11 @@ Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Added
+
+- Added support for using 32-bit Windows VST3 plugins in 64-bit Linux VST3
+  hosts.
+
 ### Fixed
 
 - Added a workaround for a bug present in every _Bluecat Audio_ VST3 plugin

README.md

@@ -180,10 +180,10 @@ ln -s "$HOME/.wine/drive_c/Program Files/Steinberg/" ~/.vst/yabridge-steinberg
 
 If you have downloaded the prebuilt version of yabridge or if have followed the
 instructions from the [bitbridge](#32-bit-bitbridge) section below, then
-yabridge is also able to load 32-bit VST2 plugins. The installation procedure
-for 32-bit plugins is exactly the same as for 64-bit plugins. Yabridge will
-automatically detect whether a plugin is 32-bit or 64-bit on startup and it will
-handle it accordingly.
+yabridge is also able to load 32-bit VST2 and VST3 plugins. The installation
+procedure for 32-bit plugins is exactly the same as for 64-bit plugins. Yabridge
+will automatically detect whether a plugin is 32-bit or 64-bit on startup and it
+will handle it accordingly.
 
 ### Wine prefixes
 

meson.build

@@ -39,6 +39,11 @@ compiler_options = [
   # https://github.com/boostorg/asio/issues/312
   '-DBOOST_ASIO_DISABLE_CONCEPTS',
 ]
+# NOTE: GCC doesn't 8-byte align doubles in structs on x86 for ABI-compatibilty
+#       reasons, but MSVC++ does. We need to force this same alignment to be
+#       ABI-compatible with 32-bit binaries created with MSVC++ on Windows.
+wine_32bit_compiler_options = ['-m32', '-malign-double']
+wine_64bit_compiler_options = ['-m64']
 
 with_bitbridge = get_option('with-bitbridge')
 with_static_boost = get_option('with-static-boost')
@@ -356,7 +361,7 @@ if with_vst3
   vst3_base_wine_64bit = static_library(
     'vst3_base_wine_64bit',
     vst3.get_variable('base_sources'),
-    cpp_args : vst3_compiler_options + vst3_wine_compiler_options + ['-m64', '-Wno-cpp'],
+    cpp_args : vst3_compiler_options + vst3_wine_compiler_options + wine_64bit_compiler_options + [ '-Wno-cpp'],
     include_directories : vst3_include_dir,
     override_options : ['warning_level=0'],
     native : false,
@@ -364,7 +369,7 @@ if with_vst3
   vst3_pluginterfaces_wine_64bit = static_library(
     'vst3_pluginterfaces_wine_64bit',
     vst3.get_variable('pluginterfaces_sources'),
-    cpp_args : vst3_compiler_options + vst3_wine_compiler_options + ['-m64'],
+    cpp_args : vst3_compiler_options + vst3_wine_compiler_options + wine_64bit_compiler_options,
     include_directories : vst3_include_dir,
     override_options : ['warning_level=0'],
     native : false,
@@ -373,7 +378,7 @@ if with_vst3
     'vst3_sdk_hosting_wine_64bit',
     vst3.get_variable('sdk_common_sources') + vst3.get_variable('sdk_hosting_sources'),
     link_with : [vst3_base_wine_64bit, vst3_pluginterfaces_wine_64bit],
-    cpp_args : vst3_compiler_options + vst3_wine_compiler_options + ['-m64', '-Wno-multichar'],
+    cpp_args : vst3_compiler_options + vst3_wine_compiler_options + wine_64bit_compiler_options + ['-Wno-multichar'],
     include_directories : vst3_include_dir,
     override_options : ['warning_level=0'],
     native : false,
@@ -392,7 +397,7 @@ if with_vst3
     vst3_base_wine_32bit = static_library(
       'vst3_base_wine_32bit',
       vst3.get_variable('base_sources'),
-      cpp_args : vst3_compiler_options + vst3_wine_compiler_options + ['-m32', '-Wno-cpp'],
+      cpp_args : vst3_compiler_options + vst3_wine_compiler_options + wine_32bit_compiler_options + ['-Wno-cpp'],
       include_directories : vst3_include_dir,
       override_options : ['warning_level=0'],
       native : false,
@@ -400,7 +405,7 @@ if with_vst3
     vst3_pluginterfaces_wine_32bit = static_library(
       'vst3_pluginterfaces_wine_32bit',
       vst3.get_variable('pluginterfaces_sources'),
-      cpp_args : vst3_compiler_options + vst3_wine_compiler_options + ['-m32'],
+      cpp_args : vst3_compiler_options + vst3_wine_compiler_options + wine_32bit_compiler_options,
       include_directories : vst3_include_dir,
       override_options : ['warning_level=0'],
       native : false,
@@ -409,7 +414,7 @@ if with_vst3
       'vst3_sdk_hosting_wine_32bit',
       vst3.get_variable('sdk_common_sources') + vst3.get_variable('sdk_hosting_sources'),
       link_with : [vst3_base_wine_32bit, vst3_pluginterfaces_wine_32bit],
-      cpp_args : vst3_compiler_options + vst3_wine_compiler_options + ['-m32', '-Wno-multichar'],
+      cpp_args : vst3_compiler_options + vst3_wine_compiler_options + wine_32bit_compiler_options + ['-Wno-multichar'],
       include_directories : vst3_include_dir,
       override_options : ['warning_level=0'],
       native : false,
@@ -539,7 +544,7 @@ executable(
   native : false,
   include_directories : include_dir,
   dependencies : host_64bit_deps,
-  cpp_args : compiler_options + ['-m64'],
+  cpp_args : compiler_options + wine_64bit_compiler_options,
   link_args : ['-m64'],
 )
 
@@ -549,7 +554,7 @@ executable(
   native : false,
   include_directories : include_dir,
   dependencies : host_64bit_deps,
-  cpp_args : compiler_options + ['-m64'],
+  cpp_args : compiler_options + wine_64bit_compiler_options,
   link_args : ['-m64'],
 )
 
@@ -560,7 +565,7 @@ if with_bitbridge
     native : false,
     include_directories : include_dir,
     dependencies : host_32bit_deps,
-    cpp_args : compiler_options + ['-m32'],
+    cpp_args : compiler_options + wine_32bit_compiler_options,
     link_args : ['-m32'],
   )
 
@@ -570,7 +575,7 @@ if with_bitbridge
     native : false,
     include_directories : include_dir,
     dependencies : host_32bit_deps,
-    cpp_args : compiler_options + ['-m32'],
+    cpp_args : compiler_options + wine_32bit_compiler_options,
     link_args : ['-m32'],
   )
 endif