Added comments

1 files changed, 15 insertions, 1 deletions

diff --git a/src/core/surface/call.c b/src/core/surface/call.c
index 3f06507f9f..e31b89489f 100644
--- a/src/core/surface/call.c
+++ b/src/core/surface/call.c
@@ -424,6 +424,11 @@ static grpc_cq_completion *allocate_completion(grpc_call *call) {
     if (call->allocated_completions & (1u << i)) {
       continue;
     }
+    /* NB: the following integer arithmetic operation needs to be in its
+     * expanded form due to the "integral promotion" performed (see section
+     * 3.2.1.1 of the C89 draft standard), which in this case upcasts the result
+     * of the bitwise OR to "unsigned". A cast to the smaller container type is
+     * then required to avoid the compiler warning */
     call->allocated_completions =
         (gpr_uint8)(call->allocated_completions | (1u << i));
     gpr_mu_unlock(&call->completion_mu);
@@ -736,6 +741,11 @@ static void finish_live_ioreq_op(grpc_call *call, grpc_ioreq_op op,
   size_t i;
   /* ioreq is live: we need to do something */
   master = &call->masters[master_set];
+  /* NB: the following integer arithmetic operation needs to be in its
+   * expanded form due to the "integral promotion" performed (see section
+   * 3.2.1.1 of the C89 draft standard), which in this case upcasts the result
+   * of the bitwise OR to "unsigned". A cast to the smaller container type is
+   * then required to avoid the compiler warning */
   master->complete_mask = (gpr_uint16)(master->complete_mask | (1u << op));
   if (!success) {
     master->success = 0;
@@ -1246,6 +1256,11 @@ static grpc_call_error start_ioreq(grpc_call *call, const grpc_ioreq *reqs,
                            GRPC_MDSTR_REF(reqs[i].data.send_status.details));
       }
     }
+    /* NB: the following integer arithmetic operation needs to be in its
+     * expanded form due to the "integral promotion" performed (see section
+     * 3.2.1.1 of the C89 draft standard), which in this case upcasts the result
+     * of the bitwise OR to "unsigned". A cast to the smaller container type is
+     * then required to avoid the compiler warning */
     have_ops = (gpr_uint16)(have_ops | (1u << op));
 
     call->request_data[op] = data;
@@ -1831,4 +1846,3 @@ void *grpc_call_context_get(grpc_call *call, grpc_context_index elem) {
 }
 
 gpr_uint8 grpc_call_is_client(grpc_call *call) { return call->is_client; }
-