Improve pkg-config-wrapper to support ChromiumOS sysroots

http://codereview.chromium.org/4516002/show had to be reverted because it
conflicts with "old style" sysroots that are still used on the arm builders.
This is a cleaner approach that should work there.

The previous approach assumed that all variables in .pc files were relative to |prefix|. It would be a desirable thing to have but in practice a few packages don't follow this and have already dereferenced |prefix| in other variables (e.g. |libdir|). So instead of forcing |prefix|, this version keeps the original one but strips the path before '/usr' (in |prefix|) from all returned paths before prepending the sysroot path.

For example if you have foo.pc:
prefix=/build/board/usr
libdir=/build/board/usr/lib  # instead of libdir=${prefix}/lib
Libs: -L${libdir}/foo -lfoo

Then instead of forcing prefix=/usr (which doesn't fix |libdir|), we find the path before '/usr' in prefix ('/build/board'), that we strip from the returned -L flag ('/build/board/usr/lib/foo' -> '/usr/lib/foo') before prepending the sysroot path (-> '/path/to/sysroot/usr/lib/foo').

BUG=None
TEST=build with sysroot=/path/to/chromiumos/chroot/build/x86-generic

Review URL: http://codereview.chromium.org/5105005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@66712 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 40 insertions, 15 deletions

diff --git a/build/linux/pkg-config-wrapper b/build/linux/pkg-config-wrapper
index d94b997..4b5455b 100755
--- a/build/linux/pkg-config-wrapper
+++ b/build/linux/pkg-config-wrapper
@@ -1,16 +1,37 @@
-#!/bin/sh
+#!/bin/bash
+# Copyright (c) 2010 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.
+
+# This program wraps around pkg-config to generate the correct include and
+# library paths when cross-compiling using a sysroot.
+# The assumption is that the sysroot contains the .pc files in usr/lib/pkgconfig
+# and usr/share/pkgconfig (relative to the sysroot) and that they output paths
+# relative to some parent path of the sysroot.
+# This assumption is valid for a range of sysroots, in particular: a
+# LSB-compliant root filesystem mounted at the sysroot, and a board build
+# directory of a Chromium OS chroot.
 
 root="$1"
 if [ -z "$root" ]
 then
-  echo "usage: $0 /path/to/sysroot [pkg-config-arguments]" >&2
+  echo "usage: $0 /path/to/sysroot [pkg-config-arguments] package" >&2
   exit 1
 fi
 
 rewrite=`dirname $0`/rewrite_dirs.py
+package=${!#}
 
 shift
 config_path=$root/usr/lib/pkgconfig:$root/usr/share/pkgconfig
 set -e
-result=`PKG_CONFIG_PATH=$config_path pkg-config --define-variable=prefix=/usr "$@"`
-echo "$result"| $rewrite $root
+# Some sysroots, like the Chromium OS ones, may generate paths that are not
+# relative to the sysroot. For example,
+# /path/to/chroot/build/x86-generic/usr/lib/pkgconfig/pkg.pc may have all paths
+# relative to /path/to/chroot (i.e. prefix=/build/x86-generic/usr) instead of
+# relative to /path/to/chroot/build/x86-generic (i.e prefix=/usr).
+# To support this correctly, it's necessary to extract the prefix to strip from
+# pkg-config's |prefix| variable.
+prefix=`PKG_CONFIG_PATH=$config_path pkg-config --variable=prefix "$package" | sed -e 's|/usr$||'`
+result=`PKG_CONFIG_PATH=$config_path pkg-config "$@"`
+echo "$result"| $rewrite --sysroot "$root" --strip-prefix "$prefix"
diff --git a/build/linux/rewrite_dirs.py b/build/linux/rewrite_dirs.py
index 5c41cf9..9e166d0 100755
--- a/build/linux/rewrite_dirs.py
+++ b/build/linux/rewrite_dirs.py
@@ -7,6 +7,7 @@
 
 import sys
 import os
+import optparse
 
 REWRITE_PREFIX = ['-I',
                   '-idirafter',
@@ -18,15 +19,19 @@ REWRITE_PREFIX = ['-I',
                   '-isystem',
                   '-L']
 
-def RewritePath(path, sysroot):
-  """Rewrites a path by prefixing it with the sysroot if it is absolute."""
+def RewritePath(path, opts):
+  """Rewrites a path by stripping the prefix and prepending the sysroot."""
+  sysroot = opts.sysroot
+  prefix = opts.strip_prefix
   if os.path.isabs(path) and not path.startswith(sysroot):
+    if path.startswith(prefix):
+      path = path[len(prefix):]
     path = path.lstrip('/')
     return os.path.join(sysroot, path)
   else:
     return path
 
-def RewriteLine(line, sysroot):
+def RewriteLine(line, opts):
   """Rewrites all the paths in recognized options."""
   args = line.split()
   count = len(args)
@@ -38,25 +43,24 @@ def RewriteLine(line, sysroot):
       if args[i] == prefix:
         i += 1
         try:
-          args[i] = RewritePath(args[i], sysroot)
+          args[i] = RewritePath(args[i], opts)
         except IndexError:
           sys.stderr.write('Missing argument following %s\n' % prefix)
           break
       elif args[i].startswith(prefix):
-        args[i] = prefix + RewritePath(args[i][len(prefix):], sysroot)
+        args[i] = prefix + RewritePath(args[i][len(prefix):], opts)
     i += 1
 
   return ' '.join(args)
 
 def main(argv):
-  try:
-    sysroot = argv[1]
-  except IndexError:
-    sys.stderr.write('usage: %s /path/to/sysroot\n' % argv[0])
-    return 1
+  parser = optparse.OptionParser()
+  parser.add_option('-s', '--sysroot', default='/', help='sysroot to prepend')
+  parser.add_option('-p', '--strip-prefix', default='', help='prefix to strip')
+  opts, args = parser.parse_args(argv[1:])
 
   for line in sys.stdin.readlines():
-    line = RewriteLine(line.strip(), sysroot)
+    line = RewriteLine(line.strip(), opts)
     print line
   return 0