gnome: Fix crash in gtkdoc and generate_gir in C++ projects

gtkdoc() and generate_gir() methods assumes there is a C compiler, but
pure C++ projects might not add it explicitly.

Fixes: #12162

2 files changed, 8 insertions, 0 deletions

diff --git a/mesonbuild/modules/__init__.py b/mesonbuild/modules/__init__.py
index 57c169d..eef67a1 100644
--- a/mesonbuild/modules/__init__.py
+++ b/mesonbuild/modules/__init__.py
@@ -167,6 +167,8 @@ class ModuleState:
             else:
                 yield self._interpreter.build_incdir_object([d])
 
+    def add_language(self, lang: str, for_machine: MachineChoice) -> None:
+        self._interpreter.add_languages([lang], True, for_machine)
 
 class ModuleObject(HoldableObject):
     """Base class for all objects returned by modules
diff --git a/mesonbuild/modules/gnome.py b/mesonbuild/modules/gnome.py
index 6bd0436..039e122 100644
--- a/mesonbuild/modules/gnome.py
+++ b/mesonbuild/modules/gnome.py
@@ -1113,6 +1113,9 @@ class GnomeModule(ExtensionModule):
     )
     def generate_gir(self, state: 'ModuleState', args: T.Tuple[T.List[T.Union[Executable, build.SharedLibrary, build.StaticLibrary]]],
                      kwargs: 'GenerateGir') -> ModuleReturnValue:
+        # Ensure we have a C compiler even in C++ projects.
+        state.add_language('c', MachineChoice.HOST)
+
         girtargets = [self._unwrap_gir_target(arg, state) for arg in args[0]]
         if len(girtargets) > 1 and any(isinstance(el, Executable) for el in girtargets):
             raise MesonException('generate_gir only accepts a single argument when one of the arguments is an executable')
@@ -1430,6 +1433,9 @@ class GnomeModule(ExtensionModule):
 
         namespace = kwargs['namespace']
 
+        # Ensure we have a C compiler even in C++ projects.
+        state.add_language('c', MachineChoice.HOST)
+
         def abs_filenames(files: T.Iterable['FileOrString']) -> T.Iterator[str]:
             for f in files:
                 if isinstance(f, mesonlib.File):