Revert "Revert "Update aosp/master libcxx rebase to r263688""

This reverts commit 1d4a1edbc7.

Change-Id: I2909937fe582f2c5552bc86e7f4d2d5cff0de0aa

utils/gen_link_script/gen_link_script.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python
+#===----------------------------------------------------------------------===##
+#
+#                     The LLVM Compiler Infrastructure
+#
+# This file is dual licensed under the MIT and the University of Illinois Open
+# Source Licenses. See LICENSE.TXT for details.
+#
+#===----------------------------------------------------------------------===##
+
+import os
+import sys
+
+def print_and_exit(msg):
+    sys.stderr.write(msg + '\n')
+    sys.exit(1)
+
+def usage_and_exit():
+    print_and_exit("Usage: ./gen_link_script.py [--help] [--dryrun] <path/to/libcxx.so> <abi_libname>")
+
+def help_and_exit():
+    help_msg = \
+"""Usage
+
+  gen_link_script.py [--help] [--dryrun] <path/to/libcxx.so> <abi_libname>
+
+  Generate a linker script that links libc++ to the proper ABI library.
+  The script replaces the specified libc++ symlink.
+  An example script for c++abi would look like "INPUT(libc++.so.1 -lc++abi)".
+
+Arguments
+  <path/to/libcxx.so> - The top level symlink to the versioned libc++ shared
+                        library. This file is replaced with a linker script.
+  <abi_libname>       - The name of the ABI library to use in the linker script.
+                        The name must be one of [c++abi, stdc++, supc++, cxxrt].
+
+Exit Status:
+  0 if OK,
+  1 if the action failed.
+"""
+    print_and_exit(help_msg)
+
+def parse_args():
+    args = list(sys.argv)
+    del args[0]
+    if len(args) == 0:
+        usage_and_exit()
+    if args[0] == '--help':
+        help_and_exit()
+    dryrun = '--dryrun' == args[0]
+    if dryrun:
+        del args[0]
+    if len(args) != 2:
+        usage_and_exit()
+    symlink_file = args[0]
+    abi_libname = args[1]
+    return dryrun, symlink_file, abi_libname
+
+def main():
+    dryrun, symlink_file, abi_libname = parse_args()
+
+    # Check that the given libc++.so file is a valid symlink.
+    if not os.path.islink(symlink_file):
+        print_and_exit("symlink file %s is not a symlink" % symlink_file)
+
+    # Read the symlink so we know what libc++ to link to in the linker script.
+    linked_libcxx = os.readlink(symlink_file)
+
+    # Check that the abi_libname is one of the supported values.
+    supported_abi_list = ['c++abi', 'stdc++', 'supc++', 'cxxrt']
+    if abi_libname not in supported_abi_list:
+        print_and_exit("abi name '%s' is not supported: Use one of %r" %
+                        (abi_libname, supported_abi_list))
+
+    # Generate the linker script contents and print the script and destination
+    # information.
+    contents = "INPUT(%s -l%s)" % (linked_libcxx, abi_libname)
+    print("GENERATING SCRIPT: '%s' as file %s" % (contents, symlink_file))
+
+    # Remove the existing libc++ symlink and replace it with the script.
+    if not dryrun:
+        os.unlink(symlink_file)
+        with open(symlink_file, 'w') as f:
+            f.write(contents + "\n")
+
+
+if __name__ == '__main__':
+    main()