plugins: enable linking with clang/lld

Windows uses a special mechanism to enable plugins to work (DLL delay
loading). Option for lld is different than ld.

MSYS2 clang based environment use lld by default, so restricting to this
config on Windows is safe, and will avoid false bug reports.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Tested-by: Stefan Weil <sw@weilnetz.de>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20250110203401.178532-4-pierrick.bouvier@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20250116160306.1709518-26-alex.bennee@linaro.org>

diff --git a/contrib/plugins/meson.build b/contrib/plugins/meson.build
index 63a32c2b4f01ff2444625063c4e40777d3877631..484b9a808c83d3aa71fc2a376dfaa66eda54705a 100644 (file)
--- a/contrib/plugins/meson.build
+++ b/contrib/plugins/meson.build
@@ -12,7 +12,7 @@ if get_option('plugins')
       t += shared_module(i, files(i + '.c') + 'win32_linker.c',
                         include_directories: '../../include/qemu',
                         link_depends: [win32_qemu_plugin_api_lib],
-                        link_args: ['-Lplugins', '-lqemu_plugin_api'],
+                        link_args: win32_qemu_plugin_api_link_flags,
                         dependencies: glib)
     else
       t += shared_module(i, files(i + '.c'),

diff --git a/meson.build b/meson.build
index da279cc1124a5cf5ea65391e715ad7da9fd0f023..15a066043b7b740b3c9c097a247a30bc40144b82 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -377,6 +377,11 @@ elif host_os == 'sunos'
   qemu_common_flags += '-D__EXTENSIONS__'
 elif host_os == 'haiku'
   qemu_common_flags += ['-DB_USE_POSITIVE_POSIX_ERRORS', '-D_BSD_SOURCE', '-fPIC']
+elif host_os == 'windows'
+  # plugins use delaylib, and clang needs to be used with lld to make it work.
+  if compiler.get_id() == 'clang' and compiler.get_linker_id() != 'ld.lld'
+    error('On windows, you need to use lld with clang - use msys2 clang64/clangarm64 env')
+  endif
 endif
 
 # Choose instruction set (currently x86-only)

diff --git a/plugins/meson.build b/plugins/meson.build
index 98542e926f8c55d1663f1144b65b55b5ff34d3a8..d60be2a4d6d06740f4e7270ff227751f9dae8bf7 100644 (file)
--- a/plugins/meson.build
+++ b/plugins/meson.build
@@ -17,14 +17,15 @@ if not enable_modules
       capture: true,
       command: ['sed', '-ne', 's/^[[:space:]]*\\(qemu_.*\\);/_\\1/p', '@INPUT@'])
     emulator_link_args += ['-Wl,-exported_symbols_list,plugins/qemu-plugins-ld64.symbols']
+  elif host_os == 'windows' and meson.get_compiler('c').get_id() == 'clang'
+    # LLVM/lld does not support exporting specific symbols. However, it works
+    # out of the box with dllexport/dllimport attribute we set in the code.
   else
     emulator_link_args += ['-Xlinker', '--dynamic-list=' + qemu_plugin_symbols.full_path()]
   endif
 endif
 
 if host_os == 'windows'
-  dlltool = find_program('dlltool', required: true)
-
   # Generate a .lib file for plugins to link against.
   # First, create a .def file listing all the symbols a plugin should expect to have
   # available in qemu
@@ -33,12 +34,27 @@ if host_os == 'windows'
     output: 'qemu_plugin_api.def',
     capture: true,
     command: ['sed', '-e', '0,/^/s//EXPORTS/; s/[{};]//g', '@INPUT@'])
+
   # then use dlltool to assemble a delaylib.
+  # The delaylib will have an "imaginary" name (qemu.exe), that is used by the
+  # linker file we add with plugins (win32_linker.c) to identify that we want
+  # to find missing symbols in current program.
+  win32_qemu_plugin_api_link_flags = ['-Lplugins', '-lqemu_plugin_api']
+  if meson.get_compiler('c').get_id() == 'clang'
+    # With LLVM/lld, delaylib is specified at link time (-delayload)
+    dlltool = find_program('llvm-dlltool', required: true)
+    dlltool_cmd = [dlltool, '-d', '@INPUT@', '-l', '@OUTPUT@', '-D', 'qemu.exe']
+    win32_qemu_plugin_api_link_flags += ['-Wl,-delayload=qemu.exe']
+  else
+    # With gcc/ld, delay lib is built with a specific delay parameter.
+    dlltool = find_program('dlltool', required: true)
+    dlltool_cmd = [dlltool, '--input-def', '@INPUT@',
+                   '--output-delaylib', '@OUTPUT@', '--dllname', 'qemu.exe']
+  endif
   win32_qemu_plugin_api_lib = configure_file(
     input: win32_plugin_def,
     output: 'libqemu_plugin_api.a',
-    command: [dlltool, '--input-def', '@INPUT@',
-              '--output-delaylib', '@OUTPUT@', '--dllname', 'qemu.exe']
+    command: dlltool_cmd
   )
 endif
 specific_ss.add(files(

diff --git a/tests/tcg/plugins/meson.build b/tests/tcg/plugins/meson.build
index f847849b1b77b211bc7003e8a92f4abe94c5b6b7..87a17d67bd4501f86990d834dcf81473b8ef0ae9 100644 (file)
--- a/tests/tcg/plugins/meson.build
+++ b/tests/tcg/plugins/meson.build
@@ -5,9 +5,8 @@ if get_option('plugins')
       t += shared_module(i, files(i + '.c') + '../../../contrib/plugins/win32_linker.c',
                         include_directories: '../../../include/qemu',
                         link_depends: [win32_qemu_plugin_api_lib],
-                        link_args: ['-Lplugins', '-lqemu_plugin_api'],
+                        link_args: win32_qemu_plugin_api_link_flags,
                         dependencies: glib)
-
     else
       t += shared_module(i, files(i + '.c'),
                         include_directories: '../../../include/qemu',