在ubuntu 下编译snappy时，在检查依赖关系时，处理autoconf的包时，在相关依赖包都已经安装的情况下，报如下错误，死活不过。
configure.ac:32: error: possibly undefined macro: AC_DEFINE
几经辗转，在*上找到解决方案：
justinclift commented on 15 Mar 2013
As possibly useful info if anyone else hits the "possibly undefined macro: AC_DEFINE" error.
That AC_DEFINE error (specifically for AC_DEFINE) can be caused by pkg-config not being installed, or at least not found in the search path.
animhotep commented on 9 Apr 2013
thanks, apt-get install pkg-config help me
安装pkg-config后，问题解决。