rt: Maintain stack ptrs correctly when returning from stack switches

Author: brson

src/rt/rust_task.h

@@ -231,6 +231,7 @@ rust_task::call_on_c_stack(void *args, void *fn_ptr) {
     // Too expensive to check
     // I(thread, on_rust_stack());
 
+    uintptr_t prev_rust_sp = next_rust_sp;
     next_rust_sp = get_sp();
 
     bool borrowed_a_c_stack = false;
@@ -251,6 +252,8 @@ rust_task::call_on_c_stack(void *args, void *fn_ptr) {
     if (borrowed_a_c_stack) {
         return_c_stack();
     }
+
+    next_rust_sp = prev_rust_sp;
 }
 
 inline void
@@ -259,11 +262,14 @@ rust_task::call_on_rust_stack(void *args, void *fn_ptr) {
     // I(thread, !on_rust_stack());
     I(thread, next_rust_sp);
 
+    uintptr_t prev_c_sp = next_c_sp;
     next_c_sp = get_sp();
 
     uintptr_t sp = sanitize_next_sp(next_rust_sp);
 
     __morestack(args, fn_ptr, sp);
+
+    next_c_sp = prev_c_sp;
 }
 
 inline void

src/test/run-pass/crust-call-deep2.rs

@@ -0,0 +1,27 @@
+native mod rustrt {
+    fn rust_dbg_call(cb: *u8,
+                     data: ctypes::uintptr_t) -> ctypes::uintptr_t;
+}
+
+crust fn cb(data: ctypes::uintptr_t) -> ctypes::uintptr_t {
+    if data == 1u {
+        data
+    } else {
+        count(data - 1u) + 1u
+    }
+}
+
+fn count(n: uint) -> uint {
+    #debug("n = %?", n);
+    rustrt::rust_dbg_call(cb, n)
+}
+
+fn main() {
+    // Make sure we're on a task with small Rust stacks (main currently
+    // has a large stack)
+    task::spawn {||
+        let result = count(1000u);
+        #debug("result = %?", result);
+        assert result == 1000u;
+    };
+}

src/test/run-pass/crust-call-scrub.rs

@@ -0,0 +1,31 @@
+// This time we're testing repeatedly going up and down both stacks to
+// make sure the stack pointers are maintained properly in both
+// directions
+
+native mod rustrt {
+    fn rust_dbg_call(cb: *u8,
+                     data: ctypes::uintptr_t) -> ctypes::uintptr_t;
+}
+
+crust fn cb(data: ctypes::uintptr_t) -> ctypes::uintptr_t {
+    if data == 1u {
+        data
+    } else {
+        count(data - 1u) + count(data - 1u)
+    }
+}
+
+fn count(n: uint) -> uint {
+    #debug("n = %?", n);
+    rustrt::rust_dbg_call(cb, n)
+}
+
+fn main() {
+    // Make sure we're on a task with small Rust stacks (main currently
+    // has a large stack)
+    task::spawn {||
+        let result = count(12u);
+        #debug("result = %?", result);
+        assert result == 2048u;
+    };
+}