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Dear LazyWeb, autoconf and #define HAVE_ 0

How do I make an existing project (let’s say, MySQL) switch from generating a config.h that has #undef HAVE_FOO to one that generates #define HAVE_FOO 0 instead?

Why? Well, here’s why:

Testing for features should be done by including “config.h” and using #if HAVE_<feature>. Use of #if (rather than #ifdef) allows the gcc -Wundef flag to warn users about features which aren’t defined 1 or 0 in config.h.

This entry was posted on Friday, March 28th, 2008 at 9:49 pm and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

4 Responses to “Dear LazyWeb, autoconf and #define HAVE_ 0”

  1. Dear LazyWeb, autoconf and #define HAVE_ … says:
    28/03/2008 at 10:57 pm

    [...] http://www.flamingspork.com/blog/2008/03/28/dear-lazyweb-autoconf-and-define-have_-0/ asks Hoosgot, [...]

  2. Erik says:
    30/03/2008 at 2:23 pm

    Well, I bogged the problem ages ago:

    http://www.mega-nerd.com/erikd/Blog/CodeHacking/autoconf_ifdef.html

  3. Erik says:
    30/03/2008 at 2:27 pm

    To make it so, you need something like this in configure.ac:

    PKG_CHECK_MODULES(SNDFILE, sndfile >= 1.0.6, ac_cv_sndfile=1, ac_cv_sndfile=0)
    AC_DEFINE_UNQUOTED([HAVE_SNDFILE],$ac_cv_sndfile,[Set to 1 if you have libsndfile.])

    HTH :-)

  4. Erik says:
    01/04/2008 at 7:12 am

    Stewart, was that of any use to you?

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