auto merge of #9096 : huonw/rust/linenoise, r=brson

- Wrap calls into linenoise in a mutex so that the functions don't have to be `unsafe` any more (fixes #3921)
- Stop leaking every line that linenoise reads.
- Handle the situation of `rl::complete(some_function); do spawn { rl::read(""); }` which would crash (`fail!` that turned into an abort, possibly due to failing with the lock locked) when the user attempted to tab-complete anything.
- Add a test for the various functions; it has to be run by hand to verify anything works, but it won't bitrot.

1 files changed, 12 insertions, 0 deletions

diff --git a/src/rt/rust_builtin.cpp b/src/rt/rust_builtin.cpp
index 03a17d2c2ef..1871e7f36b3 100644
--- a/src/rt/rust_builtin.cpp
+++ b/src/rt/rust_builtin.cpp
@@ -633,6 +633,18 @@ rust_drop_env_lock() {
     env_lock.unlock();
 }
 
+static lock_and_signal linenoise_lock;
+
+extern "C" CDECL void
+rust_take_linenoise_lock() {
+    linenoise_lock.lock();
+}
+
+extern "C" CDECL void
+rust_drop_linenoise_lock() {
+    linenoise_lock.unlock();
+}
+
 extern "C" CDECL unsigned int
 rust_valgrind_stack_register(void *start, void *end) {
   return VALGRIND_STACK_REGISTER(start, end);