Auto merge of #37833 - sfackler:process-abort, r=alexcrichton

Add std::process::abort

This calls libc abort on Unix and fastfail on Windows, first running
cleanups to do things like flush stdout buffers. This matches with libc
abort's behavior, which flushes open files.

r? @alexcrichton

src/libstd/process.rs

@@ -825,6 +825,21 @@ pub fn exit(code: i32) -> ! {
     ::sys::os::exit(code)
 }
 
+/// Terminates the process in an abnormal fashion.
+///
+/// The function will never return and will immediately terminate the current
+/// process in a platform specific "abnormal" manner.
+///
+/// Note that because this function never returns, and that it terminates the
+/// process, no destructors on the current stack or any other thread's stack
+/// will be run. If a clean shutdown is needed it is recommended to only call
+/// this function at a known point where there are no more destructors left
+/// to run.
+#[unstable(feature = "process_abort", issue = "37838")]
+pub fn abort() -> ! {
+    unsafe { ::sys::abort_internal() };
+}
+
 #[cfg(all(test, not(target_os = "emscripten")))]
 mod tests {
     use io::prelude::*;