Add shared_library argument for a Visual Studio module definitions file

On MSVC, shared libraries only export symbols that have been explicitly exported
either as part of the symbol prototype or via a module definitions file.

On compilers other than MSVC, all symbols are exported in the shared library by
default and the format for the list of symbols to export is different, so this
is only used with the VisualStudio compiler.

The module defs file path can either be relative to the current source directory
or an absolute path using meson.source_root() + '/some/path'

3 files changed, 17 insertions, 1 deletions

diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index 8e8fa42..29ce8cd 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -1657,6 +1657,8 @@ rule FORTRAN_DEP_HACK
             else:
                 soversion = None
             commands += linker.get_soname_args(target.name, abspath, soversion)
+            if target.vs_module_defs and hasattr(linker, 'gen_vs_module_defs_args'):
+                commands += linker.gen_vs_module_defs_args(target.vs_module_defs.rel_to_builddir(self.build_to_src))
         elif isinstance(target, build.StaticLibrary):
             commands += linker.get_std_link_args()
         else:
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index ab9d0d5..8732987 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -47,7 +47,7 @@ known_shlib_kwargs.update({'version' : True,
                            'soversion' : True,
                            'name_prefix' : True,
                            'name_suffix' : True,
-                           })
+                           'vs_module_defs' : True})
 
 backslash_explanation = \
 '''Compiler arguments have a backslash "\\" character. This is unfortunately not
@@ -703,6 +703,7 @@ class SharedLibrary(BuildTarget):
     def __init__(self, name, subdir, subproject, is_cross, sources, objects, environment, kwargs):
         self.version = None
         self.soversion = None
+        self.vs_module_defs = None
         super().__init__(name, subdir, subproject, is_cross, sources, objects, environment, kwargs);
         if len(self.sources) > 0 and self.sources[0].endswith('.cs'):
             prefix = 'lib'
@@ -726,6 +727,12 @@ class SharedLibrary(BuildTarget):
             self.set_version(kwargs['version'])
         if 'soversion' in kwargs:
             self.set_soversion(kwargs['soversion'])
+        if 'vs_module_defs' in kwargs:
+            path = kwargs['vs_module_defs']
+            if (os.path.isabs(path)):
+                self.vs_module_defs = File.from_absolute_file(path)
+            else:
+                self.vs_module_defs = File.from_source_file(environment.source_dir, self.subdir, path)
 
     def check_unknown_kwargs(self, kwargs):
         self.check_unknown_kwargs_int(kwargs, known_shlib_kwargs)
diff --git a/mesonbuild/compilers.py b/mesonbuild/compilers.py
index f1868dd..ff2df56 100644
--- a/mesonbuild/compilers.py
+++ b/mesonbuild/compilers.py
@@ -1252,6 +1252,13 @@ class VisualStudioCCompiler(CCompiler):
     def get_std_shared_lib_link_args(self):
         return ['/DLL']
 
+    def gen_vs_module_defs_args(self, defsfile):
+        if not isinstance(defsfile, str):
+            raise RuntimeError('Module definitions file should be str')
+        # With MSVC, DLLs only export symbols that are explicitly exported,
+        # so if a module defs file is specified, we use that to export symbols
+        return ['/DEF:' + defsfile]
+
     def gen_pch_args(self, header, source, pchname):
         objname = os.path.splitext(pchname)[0] + '.obj'
         return (objname, ['/Yc' + header, '/Fp' + pchname, '/Fo' + objname ])