Add link_syms parameter to build targets

This parameter provides a place to add -Wl,--defsym=a=b and
-Wl,--undefined=c parameters during linking. These should occur before
any object files and must occur before any libraries so that the
results will affect the link correctly.

In the ninjabackend, this is done by adding these to the ARGS
parameter during linking as that is placed in the command line before
any input files or libraries.

Signed-off-by: Keith Packard <[email protected]>

docs/yaml/functions/_build_target_base.yaml

@@ -103,6 +103,12 @@ kwargs:
       Flags to use during linking. You can use UNIX-style
       flags here for all platforms.
 
+  link_syms:
+    type: list[str]
+    description: |
+      Flags to define and undefine symbols during linking. You must use
+      build-system-appropriate flags here.
+
   link_depends:
     type: str | file | custom_tgt | custom_idx
     description: |

mesonbuild/backend/ninjabackend.py

@@ -3558,15 +3558,19 @@ def generate_link(self, target: build.BuildTarget, outname, obj_list, linker: T.
         elem.add_dep(dep_targets + custom_target_libraries)
 
         # Compiler args must be included in TI C28x linker commands.
+        compile_args = []
         if linker.get_id() in {'c2000', 'c6000', 'ti'}:
-            compile_args = []
             for for_machine in MachineChoice:
                 clist = self.environment.coredata.compilers[for_machine]
                 for langname, compiler in clist.items():
                     if langname in {'c', 'cpp'} and compiler.get_id() in {'c2000', 'c6000', 'ti'}:
                         compile_args += self.generate_basic_compiler_args(target, compiler)
-            elem.add_item('ARGS', compile_args)
 
+        # Add -Wl,--defsym and -Wl,--undefined args
+        if not isinstance(target, build.StaticLibrary):
+            compile_args += linker.get_target_link_syms(target)
+        if compile_args:
+            elem.add_item('ARGS', compile_args)
         elem.add_item('LINK_ARGS', commands)
         self.create_target_linker_introspection(target, linker, commands)
         return elem

mesonbuild/build.py

@@ -84,6 +84,7 @@ class DFeatures(TypedDict):
     'link_with',
     'link_whole',
     'link_args',
+    'link_syms',
     'link_depends',
     'implicit_include_directories',
     'include_directories',
@@ -1151,6 +1152,10 @@ def process_kwargs(self, kwargs):
                     or build_rpath properties instead.
                     This will become a hard error in a future Meson release.
                 '''))
+        self.link_syms = extract_as_list(kwargs, 'link_syms')
+        for i in self.link_syms:
+            if not isinstance(i, str):
+                raise InvalidArguments('Link_syms arguments must be strings.')
         self.process_link_depends(kwargs.get('link_depends', []))
         # Target-specific include dirs must be added BEFORE include dirs from
         # internal deps (added inside self.add_deps()) to override them.

mesonbuild/compilers/compilers.py

@@ -1038,6 +1038,9 @@ def get_soname_args(self, env: 'Environment', prefix: str, shlib_name: str,
     def get_target_link_args(self, target: 'BuildTarget') -> T.List[str]:
         return target.link_args
 
+    def get_target_link_syms(self, target: 'BuildTarget') -> T.List[str]:
+        return target.link_syms
+
     def get_dependency_compile_args(self, dep: 'Dependency') -> T.List[str]:
         return dep.get_compile_args()
 

mesonbuild/interpreter/type_checking.py

@@ -646,6 +646,13 @@ def _name_suffix_validator(arg: T.Optional[T.Union[str, T.List]]) -> T.Optional[
         validator=in_set_validator(set(compilers.all_languages)),
         since='0.51.0',
     ),
+    KwargInfo(
+        'link_syms',
+        (ContainerTypeInfo(list, str), NoneType),
+        listify=True,
+        default=None,
+        since='1.7.0',
+    ),
 ]
 
 def _validate_win_subsystem(value: T.Optional[str]) -> T.Optional[str]: