Ignore upcall_flush for channels that are disassociated from ports. This makes task-comm-10 break a little less hard, but it still leaks because messages pending in the channel are never freed.

src/rt/circular_buffer.cpp

@@ -142,3 +142,8 @@ bool
 circular_buffer::is_empty() {
     return _unread == 0;
 }
+
+size_t
+circular_buffer::size() {
+    return _unread;
+}

src/rt/circular_buffer.h

@@ -21,6 +21,7 @@ public:
     void dequeue(void *dst);
     uint8_t *peek();
     bool is_empty();
+    size_t size();
 
 private:
     // Size of the buffer in bytes, should always be a power of two so that

src/rt/rust_port.cpp

@@ -54,9 +54,9 @@ void rust_port::log_state() {
     for (uint32_t i = 0; i < chans.length(); i++) {
         rust_chan *chan = chans[i];
         task->log(rust_log::COMM,
-            "\tchan: 0x%" PRIxPTR ", data pending: %s, remote: %s",
+            "\tchan: 0x%" PRIxPTR ", size: %d, remote: %s",
             chan,
-            !chan->buffer.is_empty() ? "yes" : "no",
+            chan->buffer.size(),
             chan == remote_channel ? "yes" : "no");
     }
 }

src/rt/rust_upcall.cpp

@@ -116,6 +116,14 @@ upcall_flush_chan(rust_task *task, rust_chan *chan) {
         return;
     }
 
+    // We cannot flush if the target port was dropped.
+    if (chan->is_associated() == false) {
+        return;
+    }
+
+    A(dom, chan->is_associated(),
+      "Channel should be associated to a port.");
+
     A(dom, chan->port->is_proxy() == false,
       "Channels to remote ports should be flushed automatically.");
 

src/test/run-pass/task-comm-10.rs

@@ -2,8 +2,7 @@ io fn start(chan[chan[str]] c) {
     let port[str] p = port();
     c <| chan(p);
     auto a <- p;
-    auto b <- p;
+    // auto b <- p; // Never read the second string.
-    // Never read the second string.
 }
 
 io fn main() {