build: recreate PerMachine object in copies

Recursively copy the value if it is a collection; this ensures
that values are not overwritten until merge() is called.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: bonzini

mesonbuild/build.py

@@ -132,6 +132,8 @@ class StaticLibraryKeywordArguments(BuildTargetKeywordArguments, total=False):
         pic: bool
         prelink: bool
 
+_T = T.TypeVar('_T')
+
 DEFAULT_STATIC_LIBRARY_NAMES: T.Mapping[str, T.Tuple[str, str]] = {
     'unix': ('lib', 'a'),
     'windows': ('', 'lib'),
@@ -404,16 +406,26 @@ def get_custom_targets(self) -> OrderedDict[str, CustomTarget]:
         return custom_targets
 
     def copy(self) -> Build:
+        def copy_value(v: _T) -> _T:
+            if isinstance(v, PerMachine):
+                return PerMachine(build=copy_value(v.build), host=copy_value(v.host))
+            if isinstance(v, (list, dict, set, OrderedDict)):
+                return v.copy()
+            return v
+
         other = Build.__new__(Build)
         for k, v in self.__dict__.items():
-            if isinstance(v, (list, dict, set, OrderedDict)):
-                v = v.copy()
-            setattr(other, k, v)
+            setattr(other, k, copy_value(v))
         return other
 
     def merge(self, other: Build) -> None:
         for k, v in other.__dict__.items():
-            setattr(self, k, v)
+            if isinstance(v, PerMachine):
+                dest = getattr(self, k)
+                dest.build = v.build
+                dest.host = v.host
+            else:
+                setattr(self, k, v)
 
     def get_static_linker(self, for_machine: MachineChoice) -> T.Optional[StaticLinker]:
         for_machine = for_machine if self.environment.is_cross_build() else MachineChoice.HOST

mesonbuild/interpreter/dependencyfallbacks.py

@@ -20,9 +20,9 @@
     from .interpreter import Interpreter
     from .kwargs import DoSubproject
     from ..dependencies.base import DependencyObjectKWs
+    from ..mesonlib import MachineChoice
     from ..options import ElementaryOptionValues, OptionDict
     from .interpreterobjects import SubprojectHolder
-    from .mesonlib import MachineChoice
 
     CandidateType: TypeAlias = T.Tuple[T.Callable[[DependencyObjectKWs, str, DoSubproject], T.Optional[Dependency]], str]