rt: Add rust_try_get_current_task

Author: brson

src/rt/rust_sched_loop.h

@@ -135,6 +135,7 @@ struct rust_sched_loop
     void place_task_in_tls(rust_task *task);
 
     static rust_task *get_task_tls();
+    static rust_task *try_get_task_tls();
 
     // Called by each task when they are ready to be destroyed
     void release_task(rust_task *task);
@@ -154,7 +155,7 @@ rust_sched_loop::get_log() {
     return _log;
 }
 
-inline rust_task* rust_sched_loop::get_task_tls()
+inline rust_task* rust_sched_loop::try_get_task_tls()
 {
     if (!tls_initialized)
         return NULL;
@@ -165,6 +166,12 @@ inline rust_task* rust_sched_loop::get_task_tls()
     rust_task *task = reinterpret_cast<rust_task *>
         (pthread_getspecific(task_key));
 #endif
+    return task;
+}
+
+inline rust_task* rust_sched_loop::get_task_tls()
+{
+    rust_task *task = try_get_task_tls();
     assert(task && "Couldn't get the task from TLS!");
     return task;
 }

src/rt/rust_task.h

@@ -619,14 +619,14 @@ rust_task::record_stack_limit() {
     record_sp_limit(stk->data + LIMIT_OFFSET + RED_ZONE_SIZE);
 }
 
-inline rust_task* rust_get_current_task() {
+inline rust_task* rust_try_get_current_task() {
     uintptr_t sp_limit = get_sp_limit();
 
     // FIXME (#1226) - Because of a hack in upcall_call_shim_on_c_stack this
     // value is sometimes inconveniently set to 0, so we can't use this
     // method of retreiving the task pointer and need to fall back to TLS.
     if (sp_limit == 0)
-        return rust_sched_loop::get_task_tls();
+        return rust_sched_loop::try_get_task_tls();
 
     // The stack pointer boundary is stored in a quickly-accessible location
     // in the TCB. From that we can calculate the address of the stack segment
@@ -642,6 +642,12 @@ inline rust_task* rust_get_current_task() {
     return stk->task;
 }
 
+inline rust_task* rust_get_current_task() {
+    rust_task* task = rust_try_get_current_task();
+    assert(task != NULL && "no current task");
+    return task;
+}
+
 //
 // Local Variables:
 // mode: C++