Fix the check for growing the circular_buffer

src/rt/circular_buffer.cpp

@@ -62,7 +62,7 @@ circular_buffer::enqueue(void *src) {
     I(dom, _unread <= _buffer_sz);
 
     // Grow if necessary.
-    if (_unread == _buffer_sz) {
+    if (_unread + unit_sz > _buffer_sz) {
         size_t new_buffer_sz = _buffer_sz << 1;
         I(dom, new_buffer_sz <= MAX_CIRCULAR_BUFFFER_SIZE);
         void *new_buffer = dom->malloc(new_buffer_sz);

src/test/run-pass/chan-poweroftwo.rs

@@ -25,8 +25,22 @@ impure fn test_init() {
     mychan <| val;
 }
 
+// Dump lots of items into the channel so it has to grow.
+// Don't trigger any assertions.
+impure fn test_grow() {
+    let port[record] myport = port();
+    auto mychan = chan(myport);
+
+    let record val = rec(val1=0i32, val2=0i32, val3=0i32);
+
+    for each (uint i in _uint.range(0u, 100u)) {
+        mychan <| val;
+    }
+}
+
 impure fn main() {
     test_init();
+    test_grow();
 }
 
 // Local Variables: