diff --git a/util/mach/mig.py b/util/mach/mig.py
index 9833c8c5..c2357338 100755
--- a/util/mach/mig.py
+++ b/util/mach/mig.py
@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 # coding: utf-8
 
-# Copyright 2014 The Crashpad Authors. All rights reserved.
+# Copyright 2019 The Crashpad Authors. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -15,143 +15,19 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import argparse
-import os
-import re
-import subprocess
 import sys
 
-def FixUserImplementation(implementation):
-  """Rewrites a MIG-generated user implementation (.c) file.
-
-  Rewrites the file at |implementation| by adding “__attribute__((unused))” to
-  the definition of any structure typedefed as “__Reply” by searching for the
-  pattern unique to those structure definitions. These structures are in fact
-  unused in the user implementation file, and this will trigger a
-  -Wunused-local-typedefs warning in gcc unless removed or marked with the
-  “unused” attribute.
-  """
-
-  file = open(implementation, 'r+')
-  contents = file.read()
-
-  pattern = re.compile('^(\t} __Reply);$', re.MULTILINE)
-  contents = pattern.sub(r'\1 __attribute__((unused));', contents)
-
-  file.seek(0)
-  file.truncate()
-  file.write(contents)
-  file.close()
-
-def FixServerImplementation(implementation):
-  """Rewrites a MIG-generated server implementation (.c) file.
-
-  Rewrites the file at |implementation| by replacing “mig_internal” with
-  “mig_external” on functions that begin with “__MIG_check__”. This makes these
-  functions available to other callers outside this file from a linkage
-  perspective. It then returns, as a list of lines, declarations that can be
-  added to a header file, so that other files that include that header file will
-  have access to these declarations from a compilation perspective.
-  """
-
-  file = open(implementation, 'r+')
-  contents = file.read()
-
-  # Find interesting declarations.
-  declaration_pattern = \
-      re.compile('^mig_internal (kern_return_t __MIG_check__.*)$',
-                 re.MULTILINE)
-  declarations = declaration_pattern.findall(contents)
-
-  # Remove “__attribute__((__unused__))” from the declarations, and call them
-  # “mig_external” or “extern” depending on whether “mig_external” is defined.
-  attribute_pattern = re.compile(r'__attribute__\(\(__unused__\)\) ')
-  declarations = ['#ifdef mig_external\nmig_external\n#else\nextern\n#endif\n' +
-                  attribute_pattern.sub('', x) +
-                  ';\n' for x in declarations]
-
-  # Rewrite the declarations in this file as “mig_external”.
-  contents = declaration_pattern.sub(r'mig_external \1', contents);
-
-  # Crashpad never implements the mach_msg_server() MIG callouts. To avoid
-  # needing to provide stub implementations, set KERN_FAILURE as the RetCode
-  # and abort().
-  routine_callout_pattern = re.compile(
-      r'OutP->RetCode = (([a-zA-Z0-9_]+)\(.+\));')
-  routine_callouts = routine_callout_pattern.findall(contents)
-  for routine in routine_callouts:
-    contents = contents.replace(routine[0], 'KERN_FAILURE; abort()')
-
-  # Include the header for abort().
-  contents = '#include <stdlib.h>\n' + contents
-
-  file.seek(0)
-  file.truncate()
-  file.write(contents)
-  file.close()
-  return declarations
-
-def FixHeader(header, declarations=[]):
-  """Rewrites a MIG-generated header (.h) file.
-
-  Rewrites the file at |header| by placing it inside an “extern "C"” block, so
-  that it declares things properly when included by a C++ compilation unit.
-  |declarations| can be a list of additional declarations to place inside the
-  “extern "C"” block after the original contents of |header|.
-  """
-
-  file = open(header, 'r+')
-  contents = file.read()
-  declarations_text = ''.join(declarations)
-  contents = '''\
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-%s
-%s
-#ifdef __cplusplus
-}
-#endif
-''' % (contents, declarations_text)
-  file.seek(0)
-  file.truncate()
-  file.write(contents)
-  file.close()
+import mig_fix
+import mig_gen
 
 def main(args):
-  parser = argparse.ArgumentParser()
-  parser.add_argument('--developer-dir', help='Path to Xcode')
-  parser.add_argument('--sdk', help='Path to SDK')
-  parser.add_argument('--include',
-                      default=[],
-                      action='append',
-                      help='Additional include directory')
-  parser.add_argument('defs')
-  parser.add_argument('user_c')
-  parser.add_argument('server_c')
-  parser.add_argument('user_h')
-  parser.add_argument('server_h')
-  parsed = parser.parse_args(args)
+    parsed = mig_gen.parse_args(args)
 
-  command = ['mig',
-             '-user', parsed.user_c,
-             '-server', parsed.server_c,
-             '-header', parsed.user_h,
-             '-sheader', parsed.server_h,
-            ]
-  if parsed.developer_dir is not None:
-    os.environ['DEVELOPER_DIR'] = parsed.developer_dir
-  if parsed.sdk is not None:
-    command.extend(['-isysroot', parsed.sdk])
-  for include in parsed.include:
-    command.extend(['-I' + include])
-  command.append(parsed.defs)
-  subprocess.check_call(command)
-  FixUserImplementation(parsed.user_c)
-  server_declarations = FixServerImplementation(parsed.server_c)
-  FixHeader(parsed.user_h)
-  FixHeader(parsed.server_h, server_declarations)
+    interface = mig_gen.MigInterface(parsed.user_c, parsed.server_c,
+                                     parsed.user_h, parsed.server_h)
+    mig_gen.generate_interface(parsed.defs, interface, parsed.include,
+                               parsed.developer_dir, parsed.sdk)
+    mig_fix.fix_interface(interface)
 
 if __name__ == '__main__':
-  sys.exit(main(sys.argv[1:]))
+    sys.exit(main(sys.argv[1:]))
diff --git a/util/mach/mig_fix.py b/util/mach/mig_fix.py
new file mode 100755
index 00000000..8cd5e4f6
--- /dev/null
+++ b/util/mach/mig_fix.py
@@ -0,0 +1,197 @@
+#!/usr/bin/env python
+# coding: utf-8
+
+# Copyright 2019 The Crashpad Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+import os
+import re
+import sys
+
+from mig_gen import MigInterface
+
+def _fix_user_implementation(implementation, fixed_implementation, header,
+                             fixed_header):
+    """Rewrites a MIG-generated user implementation (.c) file.
+
+    Rewrites the file at |implementation| by adding
+    “__attribute__((unused))” to the definition of any structure typedefed
+    as “__Reply” by searching for the pattern unique to those structure
+    definitions. These structures are in fact unused in the user
+    implementation file, and this will trigger a -Wunused-local-typedefs
+    warning in gcc unless removed or marked with the “unused” attribute.
+    Also changes header references to point to the new header filename, if
+    changed.
+
+    If |fixed_implementation| is None, overwrites the original; otherwise, puts
+    the result in the file at |fixed_implementation|.
+    """
+
+    file = open(implementation, 'r+' if fixed_implementation is None else 'r')
+    contents = file.read()
+
+    pattern = re.compile('^(\t} __Reply);$', re.MULTILINE)
+    contents = pattern.sub(r'\1 __attribute__((unused));', contents)
+
+    if fixed_header is not None:
+        contents = contents.replace(
+            '#include "%s"' % os.path.basename(header),
+            '#include "%s"' % os.path.basename(fixed_header))
+
+    if fixed_implementation is None:
+        file.seek(0)
+        file.truncate()
+    else:
+        file.close()
+        file = open(fixed_implementation, 'w')
+    file.write(contents)
+    file.close()
+
+def _fix_server_implementation(implementation, fixed_implementation, header,
+                               fixed_header):
+    """Rewrites a MIG-generated server implementation (.c) file.
+
+    Rewrites the file at |implementation| by replacing “mig_internal” with
+    “mig_external” on functions that begin with “__MIG_check__”. This makes
+    these functions available to other callers outside this file from a linkage
+    perspective. It then returns, as a list of lines, declarations that can be
+    added to a header file, so that other files that include that header file
+    will have access to these declarations from a compilation perspective. Also
+    changes header references to point to the new header filename, if changed.
+
+    If |fixed_implementation| is None or not provided, overwrites the original;
+    otherwise, puts the result in the file at |fixed_implementation|.
+    """
+
+    file = open(implementation, 'r+' if fixed_implementation is None else 'r')
+    contents = file.read()
+
+    # Find interesting declarations.
+    declaration_pattern = \
+        re.compile('^mig_internal (kern_return_t __MIG_check__.*)$',
+                   re.MULTILINE)
+    declarations = declaration_pattern.findall(contents)
+
+    # Remove “__attribute__((__unused__))” from the declarations, and call them
+    # “mig_external” or “extern” depending on whether “mig_external” is defined.
+    attribute_pattern = re.compile(r'__attribute__\(\(__unused__\)\) ')
+    declarations = ['''\
+#ifdef mig_external
+mig_external
+#else
+extern
+#endif
+''' + attribute_pattern.sub('', x) + ';\n' for x in declarations]
+
+    # Rewrite the declarations in this file as “mig_external”.
+    contents = declaration_pattern.sub(r'mig_external \1', contents);
+
+    # Crashpad never implements the mach_msg_server() MIG callouts. To avoid
+    # needing to provide stub implementations, set KERN_FAILURE as the RetCode
+    # and abort().
+    routine_callout_pattern = re.compile(
+        r'OutP->RetCode = (([a-zA-Z0-9_]+)\(.+\));')
+    routine_callouts = routine_callout_pattern.findall(contents)
+    for routine in routine_callouts:
+        contents = contents.replace(routine[0], 'KERN_FAILURE; abort()')
+
+    # Include the header for abort().
+    contents = '#include <stdlib.h>\n' + contents
+
+    if fixed_header is not None:
+        contents = contents.replace(
+            '#include "%s"' % os.path.basename(header),
+            '#include "%s"' % os.path.basename(fixed_header))
+
+    if fixed_implementation is None:
+        file.seek(0)
+        file.truncate()
+    else:
+        file.close()
+        file = open(fixed_implementation, 'w')
+    file.write(contents)
+    file.close()
+    return declarations
+
+def _fix_header(header, fixed_header, declarations=[]):
+    """Rewrites a MIG-generated header (.h) file.
+
+    Rewrites the file at |header| by placing it inside an “extern "C"” block, so
+    that it declares things properly when included by a C++ compilation unit.
+    |declarations| can be a list of additional declarations to place inside the
+    “extern "C"” block after the original contents of |header|.
+
+    If |fixed_header| is None or not provided, overwrites the original;
+    otherwise, puts the result in the file at |fixed_header|.
+    """
+
+    file = open(header, 'r+' if fixed_header is None else 'r')
+    contents = file.read()
+    declarations_text = ''.join(declarations)
+    contents = '''\
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+%s
+%s
+#ifdef __cplusplus
+}
+#endif
+''' % (contents, declarations_text)
+
+    if fixed_header is None:
+        file.seek(0)
+        file.truncate()
+    else:
+        file.close()
+        file = open(fixed_header, 'w')
+    file.write(contents)
+    file.close()
+
+def fix_interface(interface, fixed_interface=None):
+    if fixed_interface is None:
+        fixed_interface = MigInterface(None, None, None, None)
+
+    _fix_user_implementation(interface.user_c, fixed_interface.user_c,
+                             interface.user_h, fixed_interface.user_h)
+    server_declarations = _fix_server_implementation(interface.server_c,
+                                                     fixed_interface.server_c,
+                                                     interface.server_h,
+                                                     fixed_interface.server_h)
+    _fix_header(interface.user_h, fixed_interface.user_h)
+    _fix_header(interface.server_h, fixed_interface.server_h,
+                server_declarations)
+
+def main(args):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('user_c')
+    parser.add_argument('--fixed_user_c', default=None)
+    parser.add_argument('server_c')
+    parser.add_argument('--fixed_server_c', default=None)
+    parser.add_argument('user_h')
+    parser.add_argument('--fixed_user_h', default=None)
+    parser.add_argument('server_h')
+    parser.add_argument('--fixed_server_h', default=None)
+    parsed = parser.parse_args(args)
+
+    interface = MigInterface(parsed.user_c, parsed.server_c,
+                             parsed.user_h, parsed.server_h)
+    fixed_interface = MigInterface(parsed.fixed_user_c, parsed.fixed_server_c,
+                                   parsed.fixed_user_h, parsed.fixed_server_h)
+    fix_interface(interface, fixed_interface)
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv[1:]))
diff --git a/util/mach/mig_gen.py b/util/mach/mig_gen.py
new file mode 100755
index 00000000..d71029a4
--- /dev/null
+++ b/util/mach/mig_gen.py
@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+# coding: utf-8
+
+# Copyright 2019 The Crashpad Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+import collections
+import os
+import subprocess
+import sys
+
+MigInterface = collections.namedtuple('MigInterface', ['user_c', 'server_c',
+                                                       'user_h', 'server_h'])
+
+def generate_interface(defs, interface, includes=[],
+                       developer_dir=None, sdk=None):
+    command = ['mig',
+               '-user', interface.user_c,
+               '-server', interface.server_c,
+               '-header', interface.user_h,
+               '-sheader', interface.server_h,
+              ]
+    if developer_dir is not None:
+        os.environ['DEVELOPER_DIR'] = developer_dir
+    if sdk is not None:
+        command.extend(['-isysroot', sdk])
+    for include in includes:
+        command.extend(['-I' + include])
+    command.append(defs)
+    subprocess.check_call(command)
+
+def parse_args(args):
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--developer-dir', help='Path to Xcode')
+    parser.add_argument('--sdk', help='Path to SDK')
+    parser.add_argument('--include',
+                        default=[],
+                        action='append',
+                        help='Additional include directory')
+    parser.add_argument('defs')
+    parser.add_argument('user_c')
+    parser.add_argument('server_c')
+    parser.add_argument('user_h')
+    parser.add_argument('server_h')
+    return parser.parse_args(args)
+
+def main(args):
+    parsed = parse_args(args)
+    interface = MigInterface(parsed.user_c, parsed.server_c,
+                             parsed.user_h, parsed.server_h)
+    generate_interface(parsed.defs, interface, parsed.include,
+                       parsed.developer_dir, parsed.sdk)
+
+if __name__ == '__main__':
+    sys.exit(main(sys.argv[1:]))