folly io_uring: properly zero initialise folly::IoUringOp

Summary: Properly zero initialize `sqe_`, `cqe_` and `iov_` in `folly::IoUringOp`.

Reviewed By: capickett

Differential Revision: D62283277

fbshipit-source-id: 58feabccaa99df5940321d3a9594a18abca2126c

Author: spikeh

folly/io/async/IoUring.cpp

@@ -114,7 +114,9 @@ void toStream(std::ostream& os, const struct io_uring_sqe& sqe) {
 namespace folly {
 
 IoUringOp::IoUringOp(NotificationCallback cb, Options options)
-    : AsyncBaseOp(std::move(cb)), options_(options) {}
+    : AsyncBaseOp(std::move(cb)), options_(options) {
+  ::memset(iov_, 0, sizeof(iov_));
+}
 
 void IoUringOp::reset(NotificationCallback cb) {
   CHECK_NE(state_, State::PENDING);

folly/io/async/IoUring.h

@@ -112,14 +112,14 @@ class IoUringOp : public AsyncBaseOp {
   union {
     struct io_uring_sqe sqe;
     uint8_t data[128];
-  } sqe_;
+  } sqe_ = {};
 
   // we have to use a union here because of -Wgnu-variable-sized-type-not-at-end
   //__u64 big_cqe[];
   union {
     __u64 user_data; // first member from from io_uring_cqe
     uint8_t data[32];
-  } cqe_;
+  } cqe_ = {};
 
   struct iovec iov_[1];
 };