src/librustc_data_structures/const_cstr.rs

   1 /// This macro creates a zero-overhead &CStr by adding a NUL terminator to
   2 /// the string literal passed into it at compile-time. Use it like:
   3 ///
   4 /// ```
   5 ///     let some_const_cstr = const_cstr!("abc");
   6 /// ```
   7 ///
   8 /// The above is roughly equivalent to:
   9 ///
  10 /// ```
  11 ///     let some_const_cstr = CStr::from_bytes_with_nul(b"abc\0").unwrap()
  12 /// ```
  13 ///
  14 /// Note that macro only checks the string literal for internal NULs if
  15 /// debug-assertions are enabled in order to avoid runtime overhead in release
  16 /// builds.
  17 #[macro_export]
  18 macro_rules! const_cstr {
  19     ($s:expr) => {{
  20         use std::ffi::CStr;
  21
  22         let str_plus_nul = concat!($s, "\0");
  23
  24         if cfg!(debug_assertions) {
  25             CStr::from_bytes_with_nul(str_plus_nul.as_bytes()).unwrap()
  26         } else {
  27             unsafe { CStr::from_bytes_with_nul_unchecked(str_plus_nul.as_bytes()) }
  28         }
  29     }};
  30 }