Necessary changes to gtest-config.in for supporting the up-coming release of...

Necessary changes to gtest-config.in for supporting the up-coming release of Google C++ Mocking Framework.  By Chandler Carruth.

scripts/gtest-config.in

 #!/bin/sh
 
 # These variables are automatically filled in by the configure script.
-prefix="@prefix@"
-exec_prefix="@exec_prefix@"
-libdir="@libdir@"
-includedir="@includedir@"
 name="@PACKAGE_TARNAME@"
 version="@PACKAGE_VERSION@"
 
-gtest_ldflags="-L${libdir}"
-gtest_libs="-l${name}"
-gtest_cppflags="-I${includedir}"
-gtest_cxxflags=""
-
 show_usage()
 {
-  cat <<EOF
-Usage: gtest-config [OPTIONS...]
-EOF
+  echo "Usage: gtest-config [OPTIONS...]"
 }
 
 show_help()
 {
   show_usage
-  cat <<EOF
-
-The \`gtest-config' script provides access to the necessary compile and linking
-flags to connect with Google C++ Testing framework. The installation queries
-may only be issued one at a time, and may not be issued with any other types of
-queries. The version queries and compiler flag queries may be combined as
-desired but not mixed. Different version queries are always combined with "and"
-logical semantics, and only the last of any particular query is used and all
-previous ones ignored. All versions must be specified as a sequence of numbers
-separated by periods. Compiler flag queries output the union of the sets of
-flags when combined.
+  cat <<\EOF
+
+The `gtest-config' script provides access to the necessary compile and linking
+flags to connect with Google C++ Testing Framework, both in a build prior to
+installation, and on the system proper after installation. The installation
+overrides may be issued in combination with any other queries, but will only
+affect installation queries if called on a built but not installed gtest. The
+installation queries may not be issued with any other types of queries, and
+only one installation query may be made at a time. The version queries and
+compiler flag queries may be combined as desired but not mixed. Different
+version queries are always combined with logical "and" semantics, and only the
+last of any particular query is used while all previous ones ignored. All
+versions must be specified as a sequence of numbers separated by periods.
+Compiler flag queries output the union of the sets of flags when combined.
 
  Examples:
   gtest-config --min-version=1.0 || echo "Insufficient Google Test version."
-  
-  gcc \$(gtest-config --cppflags --cxxflags) -o foo.o -c foo.cpp
-  gcc \$(gtest-config --ldflags --libs) -o foo foo.o
+
+  g++ $(gtest-config --cppflags --cxxflags) -o foo.o -c foo.cpp
+  g++ $(gtest-config --ldflags --libs) -o foo foo.o
+
+  # When using a built but not installed Google Test:
+  g++ $(../../my_gtest_build/scripts/gtest-config ...) ...
+
+  # When using an installed Google Test, but with installation overrides:
+  export GTEST_PREFIX="/opt"
+  g++ $(gtest-config --libdir="/opt/lib64" ...) ...
 
  Help:
   --usage                    brief usage information
   --help                     display this help message
 
+ Installation Overrides:
+  --prefix=<dir>             overrides the installation prefix
+  --exec-prefix=<dir>        overrides the executable installation prefix
+  --libdir=<dir>             overrides the library installation prefix
+  --includedir=<dir>         overrides the header file installation prefix
+
  Installation Queries:
   --prefix                   installation prefix
   --exec-prefix              executable installation prefix
   --libdir                   library installation directory
   --includedir               header file installation directory
-  --version                  the version of the INC installation
+  --version                  the version of the Google Test installation
 
  Version Queries:
   --min-version=VERSION      return 0 if the version is at least VERSION
@@ -68,11 +73,13 @@ EOF
 
 # This function bounds our version with a min and a max. It uses some clever
 # POSIX-compliant variable expansion to portably do all the work in the shell
-# and avoid any dependency on a particular "sed" implementation. Notable is
-# that it will only ever compare the first 3 components of versions. Further
-# components will be cleanly stripped off. All versions must be unadorned, so
-# "v1.0" will *not* work. The minimum version must be in $1, and the max in
-# $2.
+# and avoid any dependency on a particular "sed" or "awk" implementation.
+# Notable is that it will only ever compare the first 3 components of versions.
+# Further components will be cleanly stripped off. All versions must be
+# unadorned, so "v1.0" will *not* work. The minimum version must be in $1, and
+# the max in $2. TODO(chandlerc@google.com): If this ever breaks, we should
+# investigate expanding this via autom4te from AS_VERSION_COMPARE rather than
+# continuing to maintain our own shell version.
 check_versions()
 {
   major_version=${version%%.*}
@@ -140,13 +147,25 @@ fi
 
 while test $# -gt 0; do
   case $1 in
-    --usage)        show_usage;         exit 0;;
-    --help)         show_help;          exit 0;;
-    --prefix)       echo $prefix;       exit 0;;
-    --exec-prefix)  echo $exec_prefix;  exit 0;;
-    --libdir)       echo $libdir;       exit 0;;
-    --includedir)   echo $includedir;   exit 0;;
-    --version)      echo $version;      exit 0;;
+    --usage)          show_usage;         exit 0;;
+    --help)           show_help;          exit 0;;
+
+    # Installation overrides
+    --prefix=*)       GTEST_PREFIX=${1#--prefix=};;
+    --exec-prefix=*)  GTEST_EXEC_PREFIX=${1#--exec-prefix=};;
+    --libdir=*)       GTEST_LIBDIR=${1#--libdir=};;
+    --includedir=*)   GTEST_INCLUDEDIR=${1#--includedir=};;
+
+    # Installation queries
+    --prefix|--exec-prefix|--libdir|--includedir|--version)
+      if test -n "${do_query}"; then
+        show_usage
+        exit 1
+      fi
+      do_query=${1#--}
+      ;;
+
+    # Version checking
     --min-version=*)
       do_check_versions=yes
       min_version=${1#--min-version=}
@@ -159,17 +178,73 @@ while test $# -gt 0; do
       do_check_versions=yes
       exact_version=${1#--exact-version=}
       ;;
-    --cppflags)     echo_cppflags=yes;;
-    --cxxflags)     echo_cxxflags=yes;;
-    --ldflags)      echo_ldflags=yes;;
-    --libs)         echo_libs=yes;;
+
+    # Compiler flag output
+    --cppflags)       echo_cppflags=yes;;
+    --cxxflags)       echo_cxxflags=yes;;
+    --ldflags)        echo_ldflags=yes;;
+    --libs)           echo_libs=yes;;
 
     # Everything else is an error
-    *)              show_usage;         exit 1;;
+    *)                show_usage;         exit 1;;
   esac
   shift
 done
 
+# These have defaults filled in by the configure script but can also be
+# overridden by environment variables or command line parameters.
+prefix="${GTEST_PREFIX:-@prefix@}"
+exec_prefix="${GTEST_EXEC_PREFIX:-@exec_prefix@}"
+libdir="${GTEST_LIBDIR:-@libdir@}"
+includedir="${GTEST_INCLUDEDIR:-@includedir@}"
+
+# We try and detect if our binary is not located at its installed location. If
+# it's not, we provide variables pointing to the source and build tree rather
+# than to the install tree. This allows building against a just-built gtest
+# rather than an installed gtest.
+bindir="@bindir@"
+this_relative_bindir=`dirname $0`
+this_bindir=`cd ${this_relative_bindir}; pwd -P`
+if test "${this_bindir}" = "${this_bindir%${bindir}}"; then
+  # The path to the script doesn't end in the bindir sequence from Autoconf,
+  # assume that we are in a build tree.
+  build_dir=`dirname ${this_bindir}`
+  src_dir=`cd ${this_bindir}/@top_srcdir@; pwd -P`
+
+  # TODO(chandlerc@google.com): This is a dangerous dependency on libtool, we
+  # should work to remove it, and/or remove libtool altogether, replacing it
+  # with direct references to the library and a link path.
+  gtest_libs="${build_dir}/lib/libgtest.la"
+  gtest_ldflags=""
+
+  # We provide hooks to include from either the source or build dir, where the
+  # build dir is always preferred. This will potentially allow us to write
+  # build rules for generated headers and have them automatically be preferred
+  # over provided versions.
+  gtest_cppflags="-I${build_dir}/include -I${src_dir}/include"
+  gtest_cxxflags=""
+else
+  # We're using an installed gtest, although it may be staged under some
+  # prefix. Assume (as our own libraries do) that we can resolve the prefix,
+  # and are present in the dynamic link paths.
+  gtest_ldflags="-L${libdir}"
+  gtest_libs="-l${name}"
+  gtest_cppflags="-I${includedir}"
+  gtest_cxxflags=""
+fi
+
+# Do an installation query if requested.
+if test -n "$do_query"; then
+  case $do_query in
+    prefix)           echo $prefix;       exit 0;;
+    exec-prefix)      echo $exec_prefix;  exit 0;;
+    libdir)           echo $libdir;       exit 0;;
+    includedir)       echo $includedir;   exit 0;;
+    version)          echo $version;      exit 0;;
+    *)                show_usage;         exit 1;;
+  esac
+fi
+
 # Do a version check if requested.
 if test "$do_check_versions" = "yes"; then
   # Make sure we didn't receive a bad combination of parameters.