如何判断是否配置并支持树外构建？

Question

I often need to build common link libraries like zlib, libpng, jpeglib, freetype, etc. for many different architectures. I prefer to do out-of-tree builds then, like so:

mkdir build_linux_x64
cd build_linux_x64
../configure
make

This usually works fine but now I have read that this will only work if the following condition is met: "The project must be enabled for out-of-tree builds, typically with the user of VPATH if using make" ( Source )

This leads me to the question: How can I tell if a project is enabled for out-of-tree builds? Will configure or make just fail if the project isn't enabled for out-of-tree builds or how should I tell?

Answer 1

If the out-of-tree build works, then you know it works :). When they say "enabled" they don't mean there's some switch or configuration option that the project has to turn on. They mean that the author of the package needs to have written their Makefile.am (or Makefile.in if they don't use automake) files to work correctly when run out-of-tree. There's no way to know whether these files are written correctly except by trying it out.

If you try it out and it doesn't work you should file a bug with the package.

Note that the standard method of creating source distribution packages with autotools forces the use of out-of-tree builds, so if they're creating their source distribution using the standard methods then it will definitely build out-of-tree correctly.