I'm quite aware of how C header files are supposed to work, but I understand your point here, considering that I'm struggling to achieve dynamic fetching and generation of the respective module/constant.

I guess the usage h2ph or even the ExtUtils::Makemaker solutions should work for that, considering how mature they should be. But that's not reality, as it seems.

For now, I'm aware of 3 different values for that specific system call constant (32 and 64 bits processor and ARM). I could use the Makefile.PL to check the environment and compare with a hash or something else, but soon or later I'll have to update it... and I'm too lazy for that. :-)