Create weak_dylibs property inside macho_rewritter

machotools/macho_rewriter.py

@@ -9,6 +9,7 @@
 from .misc import _install_name_macho, _change_id_dylib_command
 from .rpath import _add_rpath_to_header, _list_rpaths_macho
 from .utils import convert_to_string, safe_update
+from .weak_load import list_weak_dylibs
 
 class _MachoRewriter(object):
     """
@@ -36,6 +37,7 @@ def __init__(self, filename):
 
         self._rpaths = _list_rpaths_macho(self._m)[0]
         self._dependencies = _list_dependencies_macho(self._m)[0]
+        self._weak_dylibs = list_weak_dylibs(self.filename)[0]
 
     def __enter__(self):
         return self
@@ -60,6 +62,10 @@ def rpaths(self):
         """
         return self._rpaths
 
+    @property
+    def weak_dylibs(self):
+        return self._weak_dylibs
+
     #----------
     # rpath API
     #----------

machotools/weak_load.py

@@ -0,0 +1,57 @@
+from macholib.ptypes import (
+	Structure
+)
+import macholib.MachO
+import macholib.mach_o
+
+from macholib.mach_o import LC_LOAD_WEAK_DYLIB, dylib
+from .utils import convert_to_string
+
+
+class weak_dylib_command(Structure):
+	_fields_ = dylib._fields_
+
+	def describe(self):
+		s = {
+			"timestamp": str(self.timestamp),
+			"current_version": str(self.current_version),
+			"compatibility_version": str(self.compatibility_version)
+		}
+		return s
+
+
+def list_weak_dylibs(filename):
+	"""Get the list of weak dylib defined in the given mach-o binary.
+
+	The returned value is a list weak dylibs such as weak_dylibs[i] is the list of weak_dylib
+	in the i-th header. For this to work, we have to create a new class specifically for
+	LC_LOAD_WEAK_DYLIB registry
+
+	Note
+	----
+	The '\0' padding at the end of each weak_dylib is stripped
+
+	Parameters
+	----------
+	filename: str
+		The path to the mach-o binary file to look at
+	"""
+
+	macholib.mach_o.LC_REGISTRY[LC_LOAD_WEAK_DYLIB] = weak_dylib_command
+	m = macholib.MachO.MachO(filename)
+	return _list_weak_dylibs_macho(m)
+
+
+def _list_weak_dylibs_macho(m):
+	weak_dylibs = []
+	for header in m.headers:
+		header_weak = []
+		weak_load_commands = [command for command in header.commands if isinstance(command[1], weak_dylib_command)]
+		for weak_load_command in weak_load_commands:
+			weak_dylib = weak_load_command[2]
+			if not weak_dylib.endswith(b"\x00"):
+				raise ValueError("Unexpected end character for weak dylib command value: %r".format(weak_dylib))
+			else:
+				header_weak.append(convert_to_string(weak_dylib))
+		weak_dylibs.append(header_weak)
+	return weak_dylibs