Macro ld_preload::ld_preload_function

macro_rules! ld_preload_function {
    (unsafe fn $realname:ident($($paramname:ident : $paramtype:ty),*) -> $ret:ty => $customname:ident $block:block) => { ... };
}

Allows to overwrite functions which are defined within C.

Example (fakeroot):

use libc::uid_t;
ld_preload_function! {
    unsafe fn getuid() -> uid_t => root_user_id {
        0
    }
}