How to Make Lua in subdirectory of a larger project autoconf?

Question

I have a C project I want to integrate with Lua.

This project has to be built on multiple platforms, so I want to build Lua in-tree with the rest of the C code, instead of depending on the system's Lua installation. Previously, we were using ax_lua macro to configure the system's Lua dependency, but I want to remove it and build Lua with the rest.

Unlike the other parts of the project, Lua already has a Makefile, and I don't want to convert this to Makefile.am just to get it converted back to Makefile.in then Makefile (unless, this is the only way.) Rather, I'd want something to the effect of running make inside the Lua folder and the rest of the build to proceed with the appropriate env vars (LUA_INCLUDE, LUA_FLAGS, LUA) set. To which files (configure.ac or Makefile.am) and what lines should I add to?

project/
  lua-5.3.6/
    Makefile
  src/
    a.c
    b.c
  configure.ac
  Makefile.am
  ...

Answer 1

Rather, I'd want something to the effect of running make inside the Lua folder and the rest of the build to proceed with the appropriate env vars (LUA_INCLUDE, LUA_FLAGS, LUA) set. To which files (configure.ac or Makefile.am) and what lines should I add to?

Unless you are willing to do it manually, it doesn't fit very well to try to build Lua before configuring the project. Moreover, even if you did build Lua manually in advance, unless you also installed it to the build system, it would be pretty optimistic to suppose that the macros from ax_lua would work as intended.

If instead you are content to build Lua via a recursive make during the overall project build, however, then the thing you're looking for is Automake's SUBDIRS variable. As its documentation describes, the subdirectories to be built do not have to be Automake-based. They just have to have makefiles (after configuration). The documentation also lists which targets the top-level makefile might try to build in the subdirectory, but it's not necessarily a showstopper if the subdirectory makefile does not support all of them. You would add this to your Makefile.am :

SUBDIRS = lua-5.3.6

The environment variables are a different question, whose answer depends in part on how the project depends on them. Probably you can just set the one you need (as make variables) in your Makefile.am . Since you are taking control of the Lua build, you can determine the needed values in advance. Everything in your Makefile.am is copied into the configured Makefile , so you don't need to do more to get those variables to the ultimate make .

For example, something along these lines might suffice:

LUA_INCLUDE = -I$(srcdir)/lua-5.3.6
LUA_LIB = lua-5.3.6/liblua-5.3.6.a

You might also consider dumping the variables in favor of just hardcoding the values, which, after all, will no longer vary.