[libcxx] [test] Fix the transitive_includes test on Windows

[mstorsjo]

Summary

The binary-mode writing to stdout can probably be written in different
ways - even though it's not as elegant as the original.

[mstorsjo]

Ping

[ldionne]

LGTM but the writing in binary mode looks really arcane, I'd like to understand why it's needed.

libcxx/test/libcxx/transitive_includes.sanitize.py

38–41

Can you explain what's the problem with the original version?

[mstorsjo]

libcxx/test/libcxx/transitive_includes.sanitize.py

38–41

The original version writes it as a text stream, so it gets \r\n newlines, which compares as different in the comparisons below.

As an alternative, we could also update the templates for generating the autogenerated parts, and making it call diff -w which ignores whitespace differences, which also should fix the issue.

[mstorsjo]

Removed kludgy code for writing to stdout in binary mode in python, switched to using diff -w for a whitespace-insensitive comparison.

[mstorsjo]

FWIW the only test failure in CI seems to be entirely unrelated to this, so if this seems ok I'll go ahead and push it later today, as this was what was discussed with Louis on discord.

libcxx/test/libcxx/transitive_includes.sanitize.py

 # of a public C++ header, excluding C compatibility headers.
 
 import os
 import re
 import sys
 
 headers = []
 for line in sys.stdin.readlines():
-  match = re.search('c\+\+/v[0-9]+/(.+)', line)
+  # On Windows, the path separators can either be forward slash or backslash.
+  # If it is a backslash, Clang prints it escaped as two consecutive
+  # backslashes, and they need to be escaped in the RE. (Use a raw string for
+  # the pattern to avoid needing another level of escaping on the Python string
+  # literal level.)
+  match = re.search(r'c\+\+(/|\\\\)v[0-9]+(/|\\\\)(.+)', line)
   if not match:
     continue
 
-  header = match.group(1)
+  header = match.group(3)
   if os.path.basename(header).endswith('.h'): # Skip C headers
     continue
 
   if os.path.basename(header).startswith('__'): # Skip internal headers
     continue
 
   headers.append(header)
 
-print('\n'.join(sorted(set(headers))))
+# Write the output to stdout in binary mode, with '\n' linebreaks on all
+# platforms.
+sys.stdout.buffer.write(bytes('\n'.join(sorted(set(headers))), 'ascii'))
+sys.stdout.buffer.write(b'\n')

libcxx/test/libcxx/transitive_includes.sh.cpp

 
 // When built with modules, this test doesn't work because --trace-includes doesn't
 // report the stack of includes correctly.
 // UNSUPPORTED: modules-build
 
 // This test uses --trace-includes, which is not supported by GCC.
 // UNSUPPORTED: gcc
 
-// This test doesn't work on AIX or Windows, but it should. Needs investigation.
-// XFAIL: buildhost=aix, buildhost=windows
+// This test doesn't work on AIX, but it should. Needs investigation.
+// XFAIL: buildhost=aix
 
 // This test is not supported when we remove the transitive includes provided for backwards
 // compatibility. When we bulk-remove them, we'll adjust the includes that are expected by
 // this test instead.
 // XFAIL: transitive-includes-disabled
 
 // Prevent <ext/hash_map> from generating deprecated warnings for this test.
 #if defined(__DEPRECATED)