How do I link a static C object file to Perl?

Question

I have a function written in C (Say in HelloWorld.c file). I want to compile this and need to create a staic object file HelloWorld.a

Finally I need to call this from a Perl program (HelloWorld.pl).

Answer 1

To call from perl to C one usually compiles a shared, not a static, library from his c code, and then loads that into the perl interpreter using the XSLoader or DynaLoader module.

To then be able to call the C code from perl space there's many ways. The most common one is writing something called XSUBs, which have a perl-side interface, map the perl calling-conventions to C calling-conventions, and call the C functions. Those XSUBs are usually also linked into the shared library that'll be loaded into perl, and written in a language called XS, which is extensively documented in perlxs and perlxstut.

There's also other ways to build that wrapper layer, like various XS code generators, as well as SWIG. But you could also call to the C functions directly using an NCI. Perl also has many of those. The P5NCI is one example of those, the ctypes module developed in this year's Google Summer of Code program is another.

Another related technique that should probably be mentioned here is Inline::C, and the other modules of the Inline family. They allow you to write code in other languages directly in perl, and call to it. Under the hood Inline::C just builds XS code and loads the result of that into the interpreter.

Answer 2

As @rafl says, you should use a shared library.

If you must use a static library, then you have to rebuild Perl with the static library built in. You'll need some XS glue too. However, this is messy enough that you really, really don't want to do it.

Answer 3

According to perlxstut:

It is commonly thought that if a system does not have the capability to dynamically load a library, you cannot build XSUBs. This is incorrect. You can build them, but you must link the XSUBs subroutines with the rest of Perl, creating a new executable. This situation is similar to Perl 4.

This tutorial can still be used on such a system. The XSUB build mechanism will check the system and build a dynamically-loadable library if possible, or else a static library and then, optionally, a new statically-linked executable with that static library linked in.

Should you wish to build a statically-linked executable on a system which can dynamically load libraries, you may, in all the following examples, where the command "make" with no arguments is executed, run the command "make perl" instead.

If you have generated such a statically-linked executable by choice, then instead of saying "make test", you should say "make test_static". On systems that cannot build dynamically-loadable libraries at all, simply saying "make test" is sufficient.