Add symbol checking script to libc++ to help manage exported symbols.

Summary:
Add symbol checking scripts for extracting a list of symbols from shared libraries and for comparing symbol lists for differences.



Reviewers: mclow.lists, danalbert, EricWF

Reviewed By: EricWF

Subscribers: majnemer, emaste, cfe-commits

Differential Revision: http://reviews.llvm.org/D4946

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@232855 91177308-0d34-0410-b5e6-96231b3b80d8

utils/sym_check/sym_diff.py

@@ -0,0 +1,47 @@
+#!/usr/bin/env python
+"""
+sym_diff - Compare two symbol lists and output the differences.
+"""
+from argparse import ArgumentParser
+import sys
+from sym_check import diff, util
+
+
+def main():
+    parser = ArgumentParser(
+        description='Extract a list of symbols from a shared library.')
+    parser.add_argument(
+        '--names-only', dest='names_only',
+        help='Only print symbol names',
+        action='store_true', default=False)
+    parser.add_argument(
+        '-o', '--output', dest='output',
+        help='The output file. stdout is used if not given',
+        type=str, action='store', default=None)
+    parser.add_argument(
+        '--demangle', dest='demangle', action='store_true', default=False)
+    parser.add_argument(
+        'old_syms', metavar='old-syms', type=str,
+        help='The file containing the old symbol list or a library')
+    parser.add_argument(
+        'new_syms', metavar='new-syms', type=str,
+        help='The file containing the new symbol list or a library')
+    args = parser.parse_args()
+
+    old_syms_list = util.extract_or_load(args.old_syms)
+    new_syms_list = util.extract_or_load(args.new_syms)
+
+    added, removed, changed = diff.diff(old_syms_list, new_syms_list)
+    report, is_break = diff.report_diff(added, removed, changed,
+                                        names_only=args.names_only,
+                                        demangle=args.demangle)
+    if args.output is None:
+        print(report)
+    else:
+        with open(args.output, 'w') as f:
+            f.write(report + '\n')
+    sys.exit(is_break)
+
+
+if __name__ == '__main__':
+    main()