rt: Expose the C stack inside the Rust scheduler so that C calls can switch to it

Author: pcwalton

src/rt/rust_scheduler.cpp

@@ -58,12 +58,10 @@ rust_scheduler::~rust_scheduler() {
 
 void
 rust_scheduler::activate(rust_task *task) {
-    context ctx;
-
-    task->ctx.next = &ctx;
+    task->ctx.next = &c_context;
     DLOG(this, task, "descheduling...");
     lock.unlock();
-    task->ctx.swap(ctx);
+    task->ctx.swap(c_context);
     lock.lock();
     DLOG(this, task, "task has returned");
 }

src/rt/rust_scheduler.h

@@ -1,6 +1,8 @@
 #ifndef RUST_SCHEDULER_H
 #define RUST_SCHEDULER_H
 
+#include "context.h"
+
 #ifndef _WIN32
 #include <pthread.h>
 #else
@@ -72,6 +74,7 @@ struct rust_scheduler : public kernel_owned<rust_scheduler>,
     static bool tls_initialized;
 
     rust_env *env;
+    context c_context;
 
     // Only a pointer to 'name' is kept, so it must live as long as this
     // domain.