I can hardly call myself an autotools expert but I do have the GNU manual
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There are two ways of playing this game:1) you could try to detect the fmod headers and library. If they are found, use them. If they are missing, search for the OpenAL headers and library and use them. If they are missing, fail the configure.2) default to FMOD. Provide the option --enable-openal in configure.ac which would disable FMOD and enable OpenAL. You want the AC_ARG_ENABLE macro.If you need more info, I recommend the autoconf manual from the GNU software site. It's pretty good (albeit large). The AC_ARG_ENABLE stuff is in section 12.2.Cheers (and THANKS!)Toby Haynes