Correctly initialize circular_buffer to a power-of-two bytes

src/rt/circular_buffer.cpp

@@ -15,7 +15,8 @@ is_power_of_two(size_t value) {
 circular_buffer::circular_buffer(rust_dom *dom, size_t unit_sz) :
     dom(dom),
     unit_sz(unit_sz),
-    _buffer_sz(INITIAL_CIRCULAR_BUFFFER_SIZE_IN_UNITS * unit_sz),
+    _buffer_sz(next_power_of_two(
+               INITIAL_CIRCULAR_BUFFFER_SIZE_IN_UNITS * unit_sz)),
     _next(0),
     _unread(0),
     _buffer((uint8_t *)dom->calloc(_buffer_sz)) {

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

@@ -0,0 +1,36 @@
+// -*- rust -*-
+
+// Regression test for circular_buffer initialization
+
+use std;
+
+import std.option;
+import std._uint;
+import std._vec;
+
+// 12-byte unit for the channel buffer. Assuming that the default
+// buffer size needs to hold 8 units, then the minimum buffer size
+// needs to be 96. That's not a power of two so needs to be rounded up.
+type record = rec(i32 val1, i32 val2, i32 val3);
+
+impure fn worker(chan[record] channel) {
+    let record val = rec(val1=0i32, val2=0i32, val3=0i32);
+    channel <| val;
+}
+
+impure fn main() {
+    let port[record] myport = port();
+    auto mychan = chan(myport);
+
+    auto temp = spawn worker(mychan);
+    auto val <- myport;
+}
+
+// Local Variables:
+// mode: rust;
+// fill-column: 78;
+// indent-tabs-mode: nil
+// c-basic-offset: 4
+// buffer-file-coding-system: utf-8-unix
+// compile-command: "make -k -C .. 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
+// End: