Criticism about java native compilation tools
I’ve been researching about java native compilation tools and found two options. Maven with nar-maven-plugin or gradle. The problem about those two is that they try to be better than they should.
Both tools give us support for compiling native code in a Java way. The problem is that they try to figure out automagically the compiler and linker that they should use. This works magically for host compilation but its a disaster for cross compilation.
Trying to know every possible compiler for every possible platform becomes an
exponential explosion problem when cross compilation enters the game. In the
eagerness to be so smart these tools have to work with some expectations, and
these expectations become a big FALSE with cross compilation. In fact these
tools depend on compiler names and this is an encapsulation problem. I’ve been
looking at nar-maven-plugin code and it has “gcc” name hardcoded. I can setup
AOL bits, or mess up with pom. But this means that to compile for X platform
I need to tweak for X, while compiling for Y need tweaks for Y. This makes me
wonder why CC and CXX where invented if people don’t use them?
It is ironic how the damn nasty make behaves nice with cross compilation just because it doesn’t try to make more than it’s work. Running recipes based on prerequisites to create targets. The compiler is deducted from environment variables and everything works fine with compilation tool not depeding on compiler. This is the beauty of simplicity my friends. Setting up tool chain is, usually, a simple matter of sourcing some file.
Another example of this guessing curse is the python extension compilation tools. It tries to guess compilation details from the python interpreter. More specific, when the interpreter is compiled some data about the compilation is saved on it self. When you compile some native extension with setuptools it use this information to guess extension compilation bits. The result is obvious. It fails with cross compilation. This is so true that the Yocto guys had to hack python so that native extensions could be compiled with easier.
The problem is simple. Compilation logic and targeting has nothing to do one with another. Changing the target SHOULD be a matter of changing the called compiler. Making targeting depending on build files (being pom.xml, build.gradle or setup.py) only serve to make crosscompilation a headache.
But still I have to admit something. While make is a simple recipe parser these tools are more about packaging than compiling it self. There is no Java or python cross compilation. This is an C and C++ problem. I’ll keep studying these guys and try to be more apprehensible about their aproaches. Maybe I came back here, and append to this post some solutions I found. Maybe not.
Cheers,