Reconf Option

When version of Autotools applications installed on host conflicts with the version of tools that generated library's building infrastructure, build process fails with the following error message.

configure.ac:7: error: version mismatch.  This is Automake 1.15.1,
configure.ac:7: but the definition used by this AM_INIT_AUTOMAKE
configure.ac:7: comes from Automake 1.15.  You should recreate
configure.ac:7: aclocal.m4 with aclocal and run automake again.
WARNING: 'automake-1.15' is probably too old.
           You should only need it if you modified 'Makefile.am' or
           'configure.ac' or m4 files included by 'configure.ac'.
           The 'automake' program is part of the GNU Automake package:
           <http://www.gnu.org/software/automake>
           It also requires GNU Autoconf, GNU m4 and Perl in order to run:
           <http://www.gnu.org/software/autoconf>
           <http://www.gnu.org/software/m4/>
           <http://www.perl.org/>

It does not happen frequently but when it does, autoreconf should be called for that external library. You can manually call it in library's source folder under src or set --reconf-LIBRARY option available in top level build scripts which does it for you automatically.

All external libraries and supplementary packages support this option except libraries listed below.

• Libraries built with CMake are not affected by this issue. There are two libraries built with CMake: snappy and libwebp.

• Some of the libraries does not come with necessary input files to run autoreconf. For them autoreconf fails with autoreconf: 'configure.ac' or 'configure.in' is required or a similar message. They are ffmpeg, freetype, libvpx and x264.