Start to fusl toolchain

fusl/tools/populate_crt.py

Index: fusl/tools/populate_crt.py
diff --git a/fusl/tools/populate_crt.py b/fusl/tools/populate_crt.py
new file mode 100644
index 0000000000000000000000000000000000000000..d9c7d679be7858ef27a23ffc11c729d3418e74d9
--- /dev/null
+++ b/fusl/tools/populate_crt.py
@@ -0,0 +1,85 @@
+# Copyright 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os.path
+import shutil
+import subprocess
+import sys
+
+
+"""Populate the compiler-provided portions of the fusl sysroot.
+
+In particular, crtbegin.o, crtend.o, and libgcc.a must be copied from
+the host sysroot to our sysroot.
+"""
+
+SYSROOT_ARTEFACTS = [
+    'crtbegin.o',

[viettrungluu, 2016/02/01 21:15:55]

I think we mostly format Python code with a 2-space indent (which is a crock,
but what can you do).

+    'crtend.o',
+    'libgcc.a',
+]
+
+
+def parse_clang_dirs(clang):
+    """Parse the output of |clang -print-search-dirs|.
+
+    This is used to find library search paths. One line of the output
+    is formatted something like:
+
+    libraries: =/usr/lib/gcc/4.8:/lib:/usr/lib
+
+    This functions strips the 'libraries: =' prefix and splits on the
+    colon, returning the list:
+
+    [ '/usr/lib/gcc/4.8', '/lib', '/usr/lib' ]
+
+    """
+
+    clang_search_dirs = subprocess.check_output([clang, '-print-search-dirs'])
+
+    library_line = None
+    library_line_prefix = 'libraries: ='
+    for line in clang_search_dirs.split('\n'):
+        if line.startswith(library_line_prefix):
+            prefix_length = len(library_line_prefix)
+            library_line = line[prefix_length:]
+            break
+    assert(library_line)
+    return library_line.split(':')
+
+
+def try_populate(library_path, target):
+    """Returns whether this path contained all the libs and we were able
+    to copy them."""
+
+    # Check that everything is here.

[viettrungluu, 2016/02/01 21:15:55]

Is it possible to find some things, but not all? (Wouldn't the search rules be
that it grabs each thing from the first thing in the search path that has it?)

[kulakowski, 2016/02/01 21:29:29]

Ah, yeah. Didn't think too much about it, since in practice it won't happen.
Will fix.

+    for artefact in SYSROOT_ARTEFACTS:

[viettrungluu, 2016/02/01 21:15:55]

In 'merika, "we" spell artifact with an "i".

[kulakowski, 2016/02/01 21:29:29]

Done.

+        path = os.path.join(library_path, artefact)
+        if not os.path.isfile(path):
+            return False
+
+    # All here, so copy!
+    for artefact in SYSROOT_ARTEFACTS:
+        source = os.path.join(library_path, artefact)
+        shutil.copy(source, target)
+
+    return True
+
+
+def main():
+    clang = sys.argv[1]
+    target = sys.argv[2]
+
+    library_paths = parse_clang_dirs(clang)
+    for library_path in library_paths:
+        if try_populate(library_path, target):
+            # If we successfully populated with one path, we are done.
+            exit(0)
+
+    # No path had what we needed, so fail.
+    exit(1)
+
+
+if __name__ == '__main__':
+    main()