func! macro lifetime mismatch for generic functions

[ffguven]

Hi,

I'm trying to mock nix::unistd::execvp which has the function signature below:

pub fn execvp<S: AsRef<CStr>>(
    filename: &CStr,
    args: &[S],
) -> Result<Infallible>

when I use InjectorPP with the lines below:

injector.when_called(injectorpp::func!(nix::unistd::execvp, fn(&std::ffi::CStr, &[&std::ffi::CStr]) -> nix::Result<std::convert::Infallible>))
        .will_execute(injectorpp::fake!(
            func_type: fn(_cmd: &std::ffi::CStr, _args: &[&std::ffi::CStr]) -> nix::Result<std::convert::Infallible>,
            returns: Err(nix::errno::Errno::E2BIG)
        )
);

I'm getting the compile time error:

error[E0308]: mismatched types
   --> src/linux_util/namespace/mod.rs:221:48
    |
221 |         injector.when_called(injectorpp::func!(nix::unistd::execvp, fn(&std::ffi::CStr, &[&std::ffi::CStr]) -> nix::Result<std::convert::Infallible>))
    |                                                ^^^^^^^^^^^^^^^^^^^  -------------------------------------------------------------------------------- expected due to this
    |                                                |
    |                                                one type is more general than the other
    |
    = note: expected fn pointer `for<'a, 'b, 'c> fn(&'a CStr, &'b [&'c CStr]) -> Result<_, _>`
                  found fn item `for<'a, 'b> fn(&'a CStr, &'b [_]) -> Result<_, _> {nix::unistd::execvp::<_>}`

My questions are:

• I couldn't manage to avoid the lifetime mismatch between my mock signature and the real execvp signature. I don't see a way to define the lifetimes for the parameters within the func! macro. Is there any ways to achieve this?
• I tried to use &'static lifetime for all the parameters in the mock signature to match the lifetime expectations and it helped me to avoid the compile time failure but the injector didn't catch the call to execvp at all.

Thanks!

[mazong1123]

Hi @ffguven, I'll need to take a closer look at the case you shared. In the mean time, could you give the unsafe API a try? Hope it can unblock you.