Add clean target

scripts/make_makefile.py

@@ -109,6 +109,10 @@ def __init__(self, options, source_path: str) -> None:
         # A path to the source tree, from the root of the build tree.
         self.source_from_build = pathlib.Path(source_path) #type: pathlib.Path
 
+        # Set of files to remove in "make clean".
+        self.clean_files = set() #type: Set[str]
+        # {extension: {directories}} to remove in "make clean"
+        self.clean_extensions = {} #type: Dict[str, Set[str]]
         # {target: help_text}
         self.help = {} #type: Dict[str, str]
         # Directories containing targets
@@ -160,6 +164,7 @@ def target(self, # pylint: disable=too-many-arguments
                dependencies: Iterable[str],
                commands: Iterable[str],
                help_text: Optional[str] = None,
+               clean=True,
                phony=False,
                ) -> None:
         """Generate a makefile rule.
@@ -169,6 +174,8 @@ def target(self, # pylint: disable=too-many-arguments
         * commands: a list of commands to run (the recipe).
         * help_text: documentation to show for this target in "make help".
           If this is omitted, the target is not listed in "make help".
+        * clean: if true, add this target to the list of files to remove
+          in "make clean". Ignored for phony targets.
         * phony: if true, declare this target as phony.
         """
         if not phony:
@@ -180,6 +187,8 @@ def target(self, # pylint: disable=too-many-arguments
             self.help[name] = help_text
         if phony:
             self.line('.PHONY: ' + name)
+        if not phony and clean:
+            self.clean_files.add(name)
 
     #### Analyze source files
 
@@ -239,7 +248,10 @@ def targets_for_c(self,
                                '$(CFLAGS)',
                                self.include_options_for(src.source_dir()),
                                '-o $@',
-                               switch, src.make_path())])
+                               switch, src.make_path())],
+                        clean=False)
+            self.clean_extensions.setdefault(extension, set())
+            self.clean_extensions[extension].add(src.target_dir())
 
     #### Generate makefile sections ####
 
@@ -275,6 +287,23 @@ def library_section(self) -> None:
                     [],
                     phony=True)
 
+    def patterns_to_clean(self) -> Iterable[str]:
+        """Yield the files and wildcard patterns to remove in "make clean"."""
+        yield from sorted(self.clean_files)
+        for extension in sorted(self.clean_extensions.keys()):
+            # It would be nice, but hard, to ensure that if the extension
+            # is empty at runtime ("$(VAR)" with VAR having an empty value)
+            # then we avoid running "rm dir/*".
+            yield sjoin(*(os.path.join(dir, '*' + extension)
+                          for dir in sorted(self.clean_extensions[extension])))
+
+    def clean_section(self) -> None:
+        """Generate a clean target."""
+        self.target('clean', [],
+                    ['$(RM) ' + arg for arg in self.patterns_to_clean()],
+                    help_text='Remove all generated files.',
+                    phony=True)
+
     def output_all(self) -> None:
         """Generate the makefile content."""
         self.comment('Generated by ' + ' '.join(sys.argv))
@@ -284,6 +313,8 @@ def output_all(self) -> None:
         self.blank_line()
         self.library_section()
         self.blank_line()
+        self.clean_section()
+        self.blank_line()
         # The help target must come last because it displays accumulated help
         # text set by previous calls to self.target. Set its own help manually
         # because self.target would set it too late for it to be printed.