Cross-compiling lwan

[fischermario]

I wanted to use lwan to create a small footprint REST API for a PLC. Unfortunately I came across a few obstacles when trying to cross-compile lwan using GCC 4.8 for the target system (ARMv7/Cortex-A8 based):

1. mimegen: it is built first to run on the host system. Unfortunately cmake cannot differentiate between targets for the host system and targets to be cross-compiled. I came up with a way to do this without hurting the build process on regular systems.
2. The compiler flag "-mtune=native" does not sit well with some (not all!) ARM systems. I have added a condition to only set the flag on x86_64.
3. Compiling common/hash.c produces the following error message (paths omitted):
   [ 50%] Building C object common/hash.c.o common/hash.c: In function 'get_random_unsigned': common/hash.c:74:32: error: 'O_CLOEXEC' undeclared (first use in this function)
   There is a simple fix for that (references: GitHub bugreport, blog post).

I have attached a patch to deal with the issues described above:
lwan-crosscompile.patch.txt

[lpereira]

Nice!

I imagined that mimegen becoming a native program rather than a Python script would be a problem for cross-compiling. Thanks for fixing this.

As for the mtune parameter, is there any way to detect if it's not going to work with a particular processor family, or is that more of a cross-compilation issue?

If the stuff you're building is open source, send me a link once Lwan is part of it so I can link to it from the readme file.

I'll test the patch as soon as I'm in front of a computer.

[fischermario]

As for the mtune parameter, is there any way to detect if it's not going to work with a particular processor family, or is that more of a cross-compilation issue?

You are right. It is better to check whether the compiler supports this particular parameter or not.

The following patch assumes that you have already applied the former:
mtune-detection.patch.txt

If the stuff you're building is open source, send me a link once Lwan is part of it so I can link to it from the readme file.

You are giving me too much credit ;-) My tool is just in its infancy. Right now I am playing around with Lwan, getting used to it, reading the example code. I already hit some walls. Lwan is a great piece of software, but it is in dire need of a proper documentation.

[lpereira]

Nice, I'll use the new patch as well.

As for hitting walls: please don't hesitate to either open issues or send me emails. That'll help me to know what to focus whenever I start writing the documentation.