Beginning work on GN build

build/config/linux/pkg-config.py

Index: build/config/linux/pkg-config.py
diff --git a/build/config/linux/pkg-config.py b/build/config/linux/pkg-config.py
new file mode 100755
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+++ b/build/config/linux/pkg-config.py
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+#!/usr/bin/env python
+# Copyright (c) 2013 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 json
+import os
+import subprocess
+import sys
+import re
+from optparse import OptionParser
+
+# This script runs pkg-config, optionally filtering out some results, and
+# returns the result.
+#
+# The result will be [ <includes>, <cflags>, <libs>, <lib_dirs>, <ldflags> ]
+# where each member is itself a list of strings.
+#
+# You can filter out matches using "-v <regexp>" where all results from
+# pkgconfig matching the given regular expression will be ignored. You can
+# specify more than one regular expression my specifying "-v" more than once.
+#
+# You can specify a sysroot using "-s <sysroot>" where sysroot is the absolute
+# system path to the sysroot used for compiling. This script will attempt to
+# generate correct paths for the sysroot.
+#
+# When using a sysroot, you must also specify the architecture via
+# "-a <arch>" where arch is either "x86" or "x64".
+#
+# CrOS systemroots place pkgconfig files at <systemroot>/usr/share/pkgconfig
+# and one of <systemroot>/usr/lib/pkgconfig or <systemroot>/usr/lib64/pkgconfig
+# depending on whether the systemroot is for a 32 or 64 bit architecture. They
+# specify the 'lib' or 'lib64' of the pkgconfig path by defining the
+# 'system_libdir' variable in the args.gn file. pkg_config.gni communicates this
+# variable to this script with the "--system_libdir <system_libdir>" flag. If no
+# flag is provided, then pkgconfig files are assumed to come from
+# <systemroot>/usr/lib/pkgconfig.
+#
+# Additionally, you can specify the option --atleast-version. This will skip
+# the normal outputting of a dictionary and instead print true or false,
+# depending on the return value of pkg-config for the given package.
+
+
+def SetConfigPath(options):
+  """Set the PKG_CONFIG_LIBDIR environment variable.
+
+  This takes into account any sysroot and architecture specification from the
+  options on the given command line.
+  """
+
+  sysroot = options.sysroot
+  assert sysroot
+
+  # Compute the library path name based on the architecture.
+  arch = options.arch
+  if sysroot and not arch:
+    print "You must specify an architecture via -a if using a sysroot."
+    sys.exit(1)
+
+  libdir = sysroot + '/usr/' + options.system_libdir + '/pkgconfig'
+  libdir += ':' + sysroot + '/usr/share/pkgconfig'
+  os.environ['PKG_CONFIG_LIBDIR'] = libdir
+  return libdir
+
+
+def GetPkgConfigPrefixToStrip(args):
+  """Returns the prefix from pkg-config where packages are installed.
+
+  This returned prefix is the one that should be stripped from the beginning of
+  directory names to take into account sysroots.
+  """
+  # Some sysroots, like the Chromium OS ones, may generate paths that are not
+  # relative to the sysroot. For example,
+  # /path/to/chroot/build/x86-generic/usr/lib/pkgconfig/pkg.pc may have all
+  # paths relative to /path/to/chroot (i.e. prefix=/build/x86-generic/usr)
+  # instead of relative to /path/to/chroot/build/x86-generic (i.e prefix=/usr).
+  # To support this correctly, it's necessary to extract the prefix to strip
+  # from pkg-config's |prefix| variable.
+  prefix = subprocess.check_output(["pkg-config", "--variable=prefix"] + args,
+      env=os.environ)
+  if prefix[-4] == '/usr':
+    return prefix[4:]
+  return prefix
+
+
+def MatchesAnyRegexp(flag, list_of_regexps):
+  """Returns true if the first argument matches any regular expression in the
+  given list."""
+  for regexp in list_of_regexps:
+    if regexp.search(flag) != None:
+      return True
+  return False
+
+
+def RewritePath(path, strip_prefix, sysroot):
+  """Rewrites a path by stripping the prefix and prepending the sysroot."""
+  if os.path.isabs(path) and not path.startswith(sysroot):
+    if path.startswith(strip_prefix):
+      path = path[len(strip_prefix):]
+    path = path.lstrip('/')
+    return os.path.join(sysroot, path)
+  else:
+    return path
+
+
+def main():
+  # If this is run on non-Linux platforms, just return nothing and indicate
+  # success. This allows us to "kind of emulate" a Linux build from other
+  # platforms.
+  if "linux" not in sys.platform:
+    print "[[],[],[],[],[]]"
+    return 0
+
+  parser = OptionParser()
+  parser.add_option('-d', '--debug', action='store_true')
+  parser.add_option('-p', action='store', dest='pkg_config', type='string',
+                    default='pkg-config')
+  parser.add_option('-v', action='append', dest='strip_out', type='string')
+  parser.add_option('-s', action='store', dest='sysroot', type='string')
+  parser.add_option('-a', action='store', dest='arch', type='string')
+  parser.add_option('--system_libdir', action='store', dest='system_libdir',
+                    type='string', default='lib')
+  parser.add_option('--atleast-version', action='store',
+                    dest='atleast_version', type='string')
+  parser.add_option('--libdir', action='store_true', dest='libdir')
+  (options, args) = parser.parse_args()
+
+  # Make a list of regular expressions to strip out.
+  strip_out = []
+  if options.strip_out != None:
+    for regexp in options.strip_out:
+      strip_out.append(re.compile(regexp))
+
+  if options.sysroot:
+    libdir = SetConfigPath(options)
+    if options.debug:
+      sys.stderr.write('PKG_CONFIG_LIBDIR=%s\n' % libdir)
+    prefix = GetPkgConfigPrefixToStrip(args)
+  else:
+    prefix = ''
+
+  if options.atleast_version:
+    # When asking for the return value, just run pkg-config and print the return
+    # value, no need to do other work.
+    if not subprocess.call([options.pkg_config,
+                            "--atleast-version=" + options.atleast_version] +
+                            args):
+      print "true"
+    else:
+      print "false"
+    return 0
+
+  if options.libdir:
+    cmd = [options.pkg_config, "--variable=libdir"] + args
+    if options.debug:
+      sys.stderr.write('Running: %s\n' % cmd)
+    try:
+      libdir = subprocess.check_output(cmd)
+    except:
+      print "Error from pkg-config."
+      return 1
+    sys.stdout.write(libdir.strip())
+    return 0
+
+  cmd = [options.pkg_config, "--cflags", "--libs"] + args
+  if options.debug:
+    sys.stderr.write('Running: %s\n' % ' '.join(cmd))
+
+  try:
+    flag_string = subprocess.check_output(cmd)
+  except:
+    sys.stderr.write('Could not run pkg-config.\n')
+    return 1
+
+  # For now just split on spaces to get the args out. This will break if
+  # pkgconfig returns quoted things with spaces in them, but that doesn't seem
+  # to happen in practice.
+  all_flags = flag_string.strip().split(' ')
+
+
+  sysroot = options.sysroot
+  if not sysroot:
+    sysroot = ''
+
+  includes = []
+  cflags = []
+  libs = []
+  lib_dirs = []
+  ldflags = []
+
+  for flag in all_flags[:]:
+    if len(flag) == 0 or MatchesAnyRegexp(flag, strip_out):
+      continue;
+
+    if flag[:2] == '-l':
+      libs.append(RewritePath(flag[2:], prefix, sysroot))
+    elif flag[:2] == '-L':
+      lib_dirs.append(RewritePath(flag[2:], prefix, sysroot))
+    elif flag[:2] == '-I':
+      includes.append(RewritePath(flag[2:], prefix, sysroot))
+    elif flag[:3] == '-Wl':
+      ldflags.append(flag)
+    elif flag == '-pthread':
+      # Many libs specify "-pthread" which we don't need since we always include
+      # this anyway. Removing it here prevents a bunch of duplicate inclusions
+      # on the command line.
+      pass
+    else:
+      cflags.append(flag)
+
+  # Output a GN array, the first one is the cflags, the second are the libs. The
+  # JSON formatter prints GN compatible lists when everything is a list of
+  # strings.
+  print json.dumps([includes, cflags, libs, lib_dirs, ldflags])
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())