Fix problem with calculation of the 'c_ast.FuncDecl' offset

[eps-id]

When parsing some legacy code the inspect module ended up with following error

error: 'Struct' object has no attribute 'args'

It turned out, that the reason was a wrong offset of self.file_ast.ext[i] handed over to function rename_parameters which then tried to replace functions parameters in 'Struct' objects.

The quick hack to solve this issue was to search for the first c_ast.FuncDecl in self.file_ast.ext and take this position as func_offset.

[eps-id]

After a short look on the failed tests ist seems to be a problem of the supplied code in the PR.
It also turned out, that the quick fix was just solving one issue caused by the legacy code but in the meantime another code snippet broke it again.

When compiling the legacy code in WSL using Ubuntu-24.04 and gcc (Ubuntu 13.3.0-6ubuntu2~24.04) 13.3.0 some part of the code pulls the following header into our translation unit.

# 27 "/usr/include/x86_64-linux-gnu/bits/types/cookie_io_functions_t.h" 3 4
typedef __ssize_t cookie_read_function_t (void *__cookie, char *__buf,
                                          size_t __nbytes);

This is accidentally parsed as "typedef" by Nala but tagged as "ast_c.FuncDecl".

As a result this function along with some others end up to be in self.typedefs_code which leads to an error later on, as "cookie_read_function_t" also is added to self.func_names.

[eerimoq]

hmm maybe I shouldn't have merged it because the testes fail =) Any change you can create a new PR with a fix?

Github actions now use Ubuntu 22.04, which fixes the weird test failures we had before.

[eps-id]

I fixed a few test on my fork, but 3 are still failing. I will check tomorrow if I can fix those to.
At least one problem comes from using a modern compiler. It seems that pycparser cannot handle __typeof__() which is uses nowadays in typedefs for nullptr_t and size_t.
But this can easily be avoided by adding -std=c11 or -std=c17 on the gcc commandline.
Are ther any thoughts on using a modern AST parser like clang.cindex which also can be used together with python?

[eerimoq]

I'm open to make pretty much any change that improves Nala. I'll not have time to make any changes myself, but can bump the version and publish new releases if needed.