Is it possible to println from the kernel?

[milewski]

How to println from a kernel? the following code throws an error:

cuda_std::println!("hello world");

  error[E0433]: failed to resolve: could not find `alloc` in the list of imported crates
    --> src/lib.rs:12:9
     |
  12 |         cuda_std::println!("hello world");
     |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ could not find `alloc` in the list of imported crates
     |
     = note: this error originates in the macro `$crate::print` which comes from the expansion of the macro `cuda_std::println` (in Nightly builds, run with -Z macro-backtrace for more info)

[karpenkoag]

If add extern function

unsafe extern "C" {
    pub fn vprintf(format: *const u8, valist: *const core::ffi::c_void) -> i32;
}

You can call

unsafe {
            vprintf(c"Hello world!\n".as_ptr().cast(), core::ptr::null());
}

But I do not know how to add parameters to such output.

[milewski]

Thanks for the hint, this works out for me:

fn log<T>(string: &str, params: T) {
    unsafe {
        core::arch::nvptx::vprintf(string.as_ptr(), transmute(&params));
    }
}

log("Hello World: %d %d [%d]", (1, 2, 3));