Create static C-compatible strings from Rust string literals.
Example
-------
```rust
#[macro_use] extern crate const_cstr;
extern crate libc;
use std::ffi::CStr;
const_cstr! {
HELLO_CSTR = "Hello, world!";
// Multiple declarations can be made with one invocation.
// GOODNIGHT_CSTR = "Goodnight, sun!";
// But only with the same visibility:
// pub GOODNIGHT_CSTR = "Goodnight, sun!";
// ^~~ Error: expected identifier, found `pub`
}
// Imagine this is an `extern "C"` function linked from some other lib.
unsafe fn print_c_string(cstr: *const libc::c_char) {
println!("{}", CStr::from_ptr(cstr).to_str().unwrap());
}
fn main() {
// When just passed a literal, returns an rvalue instead.
let goodnight_cstr = const_cstr!("Goodnight, sun!");
unsafe {
print_c_string(HELLO_CSTR.as_ptr());
print_c_string(goodnight_cstr.as_ptr());
}
}
```
Prints:
```notest
Hello, world!
Goodnight, sun!
```