1.1 Linking code with the library

This package installs a data file for pkg-config, so when searching for the installed library with the GNU Autotools, we can add the following macro use to configure.ac:

PKG_CHECK_MODULES([CRE2],[cre2 >= 0.1.0])

which will set the variables CRE2_LIBS and CRE2_CFLAGS. The macros for GNU Autoconf installed by pkg-config are documented in the manual page pkg-config(1). To avoid problems with pkg-config, we need to remember that:

• The macro file defining PKG_CHECK_MODULES is installed by the package pkg-config; such file usually is in one of the locations:
  /usr/share/aclocal/pkg.m4
  /usr/local/share/aclocal/pkg.m4
• The macro file is located by aclocal, which in turn is installed by the package GNU Automake; aclocal is used by autoreconf. We must make sure that aclocal finds all the installed macro files; for this purpose we can use the environment variable ACLOCAL_PATH. To include all the common possible directories, we can add the following chunk of Bourne shell code to our shell profile file:

  ACLOCAL_PATH=
  for dir in \
      /share/aclocal              \
      /usr/share/aclocal          \
      /usr/local/share/aclocal
  do
      if test -d "$dir"
      then
          if test -n "$ACLOCAL_PATH"
          then ACLOCAL_PATH=${dir}:${ACLOCAL_PATH}
          else ACLOCAL_PATH=${dir}
          fi
      fi
  done
  export ACLOCAL_PATH
  

• The executable pkg-config searches for the package data files in a set of directories; we can configure the search path with the environment variable PKG_CONFIG_PATH. To include all the common possible directories, we can add the following chunk of Bourne shell code to our shell profile file:

  PKG_CONFIG_PATH=
  for dir in \
      /lib/pkgconfig              \
      /lib64/pkgconfig            \
      /share/pkgconfig            \
      /usr/lib/pkgconfig          \
      /usr/lib64/pkgconfig        \
      /usr/share/pkgconfig        \
      /usr/local/lib/pkgconfig    \
      /usr/local/lib64/pkgconfig  \
      /usr/local/share/pkgconfig
  do
      if test -d "$dir"
      then
          if test -n "$PKG_CONFIG_PATH"
          then PKG_CONFIG_PATH=${dir}:${PKG_CONFIG_PATH}
          else PKG_CONFIG_PATH=${dir}
          fi
      fi
  done
  export PKG_CONFIG_PATH
  

Alternatively we can use the raw GNU Autoconf macros:

AC_CHECK_LIB([cre2],[cre2_version_string],,
  [AC_MSG_FAILURE([test for C wrapper for RE2 library failed])])
AC_CHECK_HEADERS([cre2.h],,
  [AC_MSG_FAILURE([test for C wrapper for RE2 header failed])])

This document describes version 0.4.0-devel.2 of CRE2.