A Makefile can be viewed as a series of shell scripts interconnected by dependency rules that dictate which elements can be safely skipped, which must be run, and in what order. I believe it's possible to recast Autoconf so that it generates a Makefile that produces the same outputs as a configure script, but which can be run under "make -jN" to run in parallel, safely. Checks for headers, functions, and libraries can generally run in parallel. In a configuration script for any sufficiently complex program, there will exist interdependencies, but the M4 macros expressing them often have a single entry point. e.g. This program requires MySQL, which requires libsocket, which requires libnsl, which... That's all one big macro, generally, so it can become a single Makefile target, producing a single set of outputs. To the extent that there are further interdependencies (e.g. this program requires the MySQL C API library because it depends on MySQL++, a C++ wrapper) Autoconf's M4 DSL could be extended to allow for SQL-like transaction blocks: these two feature-test macros have to be handled in sequence. I don't want it bad enough to write it. I just think it's possible, and within reach, without straining the nature of Autoconf too badly.
