From 92fcb61f7d9849592bf8708d6cdc0f09f4d1bade Mon Sep 17 00:00:00 2001
From: Ingo Mueller <ingo.mueller@inf.ethz.ch>
Date: Fri, 3 Jul 2020 14:38:05 +0200
Subject: [PATCH] Fix undefined behavior.

The original version used IO control blocks from the stack, which will
be overwritten after the function has returned. However, IO control
blocks should live until the IO has completed.
---
 README.md | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index fa548ef..6939c81 100644
--- a/README.md
+++ b/README.md
@@ -157,6 +157,7 @@ static const int kPageSize = 4096;
 class AIORequest {
  public:
   int* buffer_;
+  struct iocb iocb_;
 
   virtual void Complete(int res) = 0;
 
@@ -237,9 +238,9 @@ class AIOAdder : public Adder {
 
   void SubmitWrite() {
     LOG(INFO) << "Submitting a write to " << counter_;
-    struct iocb iocb;
-    struct iocb* iocbs = &iocb;
     AIORequest *req = new AIOWriteRequest(counter_);
+    struct iocb& iocb = req->iocb_;
+    struct iocb* iocbs = &iocb;
     io_prep_pwrite(&iocb, fd_, req->buffer_, kPageSize, counter_ * kPageSize);
     iocb.data = req;
     int res = io_submit(ioctx_, 1, &iocbs);
@@ -257,9 +258,9 @@ class AIOAdder : public Adder {
 
   void SubmitRead() {
     LOG(INFO) << "Submitting a read from " << counter_;
-    struct iocb iocb;
-    struct iocb* iocbs = &iocb;
     AIORequest *req = new AIOReadRequest(this);
+    struct iocb& iocb = req->iocb_;
+    struct iocb* iocbs = &iocb;
     io_prep_pread(&iocb, fd_, req->buffer_, kPageSize, counter_ * kPageSize);
     iocb.data = req;
     int res = io_submit(ioctx_, 1, &iocbs);