Implement a tool called link_limiter to impose a global restriction on how many

tools/win/link_limiter/build_link_limiter.py

Index: tools/win/link_limiter/build_link_limiter.py
diff --git a/tools/win/link_limiter/build_link_limiter.py b/tools/win/link_limiter/build_link_limiter.py
new file mode 100644
index 0000000000000000000000000000000000000000..7a9bd4f40d03ea98db54fbd7c119083f9dd683c5
--- /dev/null
+++ b/tools/win/link_limiter/build_link_limiter.py
@@ -0,0 +1,99 @@
+#!/usr/bin/env python
+# Copyright (c) 2012 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 glob
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+
+BUILD_DIR = "build"

[cmp, 2012/08/01 22:23:53]

nit: single quotes

+
+
+def run_with_vsvars(cmd, tmpdir=None):
+  fd, filename = tempfile.mkstemp('.bat', text=True)
+  with os.fdopen(fd, "w") as f:

[cmp, 2012/08/01 22:23:53]

nit: single quotes

+    print >> f, '@echo off'
+    print >> f, r'call "%VS100COMNTOOLS%\vsvars32.bat"'
+    if tmpdir:
+      print >> f, r'cd %s' % tmpdir
+    print >> f, cmd
+  try:
+    p = subprocess.Popen([filename], shell=True, stdout=subprocess.PIPE,
+        universal_newlines=True)
+    out, _ = p.communicate()
+    return p.returncode, out
+  finally:
+    os.unlink(filename)
+
+
+def get_vc_dir():
+  _, out = run_with_vsvars('echo VCINSTALLDIR=%VCINSTALLDIR%')
+  for line in out.splitlines():  # pylint: disable-msg=E1103
+    if line.startswith('VCINSTALLDIR='):
+      return line[len('VCINSTALLDIR='):]
+  return None
+
+
+def build(infile):
+  if not os.path.exists(BUILD_DIR):
+    os.makedirs(BUILD_DIR)
+  outfile = 'limiter.exe'
+  outpath = os.path.join(BUILD_DIR, outfile)
+  cpptime = os.path.getmtime(infile)
+  if not os.path.exists(outpath) or cpptime > os.path.getmtime(outpath):

[nsylvain, 2012/08/01 18:53:46]

do you really need the optimization for the time? This is a manual process
right? And this is a small file.  We should probably just build it all the time?

[iannucci, 2012/08/01 19:09:53]

This was a holdover from the supalink code. I can remove it. I figured that
since it was there I'd keep it :)

+    print 'Building %s...' % outfile
+    rc, out = run_with_vsvars(
+        'cl /nologo /Ox /Zi /W4 /WX /D_UNICODE /DUNICODE'
+        ' /D_CRT_SECURE_NO_WARNINGS /EHsc'
+        ' %s /link /out:%s' % (os.path.join("..", infile), outfile), BUILD_DIR)
+    if rc:
+      print out
+      print 'Failed to build %s' % outfile
+      sys.exit(1)
+  else:
+    print "%s already built" % outfile
+  return outpath
+
+
+def main():
+  if sys.argv[-1] == 'clean':
+    if os.path.exists(BUILD_DIR):

[nsylvain, 2012/08/01 18:53:46]

Slightly afraid someone would do  : cd src\ && python
tools\win\link_limiter\build_link_limiter.py and get their src\build directory
destroyed.   Can we make it an absolute path instead?

+      shutil.rmtree(BUILD_DIR)
+    for exe in glob.glob('*.exe'):
+      os.unlink(exe)
+    return 0
+
+  vcdir = os.environ.get('VCINSTALLDIR')
+  if not vcdir:
+    vcdir = get_vc_dir()
+    if not vcdir:
+      print "Couldn't get VCINSTALLDIR. Run vsvars32.bat?"
+      return 1
+    os.environ['PATH'] += (';' + os.path.join(vcdir, 'bin') +
+                           ';' + os.path.join(vcdir, r'..\Common7\IDE'))
+
+  # Switch to our own dir.
+  os.chdir(os.path.dirname(os.path.abspath(__file__)))

[nsylvain, 2012/08/01 18:53:46]

or maybe you can just run this before checking for the BUILD_DIR

[iannucci, 2012/08/01 19:09:53]

yeah good call. I'll make the script normalize itself relative to __file__
earlier

+
+  # Verify that we can find link.exe.
+  link = os.path.join(vcdir, 'bin', 'link.exe')
+  if not os.path.exists(link):
+    print 'link.exe not found at %s' % link
+    return 1
+
+  exe_name = build('limiter.cpp')
+  for shim_exe in "lib.exe link.exe".split():

[nsylvain, 2012/08/01 18:53:46]

why the .split? why not for shim_exe in('lib.exe', 'link.exe'):

Also, we should use single quotes everywhere.

[iannucci, 2012/08/01 19:09:53]

I tend to lose split b/c less punctuation. I'll tuple-ify it.

[iannucci, 2012/08/01 19:16:22]

Er... 'use' split.

+    newpath = "%s__LIMITER.exe" % shim_exe

[nsylvain, 2012/08/01 18:53:46]

single quotes

[iannucci, 2012/08/01 19:09:53]

Why single quotes (curious)? Python makes no distinction between the two (except
w.r.t. escaping the quotes of the same gender), and I don't see anything in the
style guide.

Bash would definitely need single quotes if possible :D

[cmp, 2012/08/01 22:23:53]

Nothing in the style guide about single versus double quotes, but the style
guide does say 'be consistent'.  So within the same file, consistency means
picking one and sticking with it unless the specific need is there for something
else.  Zoom out and you'll find we support a bunch of Python code and work on a
variety of areas, and we still want to be consistent across all of those.  So
when it comes to choosing which of the two to pick for the whole file, we pick
single quotes in order to stay consistent across all of the Python files we
maintain in tools/build and src/.

I would not be surprised if there were files in other parts of src/ that aren't
consistent with this approach (or even aren't consistent within the same file). 
We fix those if we run into those cases and have to, assuming there's no
objection.
Don't get us started on bash. :)

+    shutil.copyfile(exe_name, newpath)
+    print '%s shim built. Use with msbuild like: "/p:LinkToolExe=%s"' \
+        % (shim_exe, os.path.abspath(newpath))
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())