From 868d78b1923f7b80ebd64e2054608cac640c0c2f Mon Sep 17 00:00:00 2001
From: ITHelpDec <34002836+ITHelpDec@users.noreply.github.com>
Date: Mon, 26 Jun 2023 22:48:55 +0100
Subject: [PATCH 1/3] change `return last` to `return`

  * "Void function 'parallel_partial_sum<std::__wrap_iter<int *>>' should not return a value"
  * example from book is actually simple `return`
---
 listings/listing_8.11.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/listings/listing_8.11.cpp b/listings/listing_8.11.cpp
index 5ea88cc..7f53915 100644
--- a/listings/listing_8.11.cpp
+++ b/listings/listing_8.11.cpp
@@ -57,7 +57,7 @@ void parallel_partial_sum(Iterator first,Iterator last)
     unsigned long const length=std::distance(first,last);
 
     if(!length)
-        return last;
+        return;
 
     unsigned long const min_per_thread=25;
     unsigned long const max_threads=

From 6d62a767145e958937feea70df15b44afe58915b Mon Sep 17 00:00:00 2001
From: ITHelpDec <34002836+ITHelpDec@users.noreply.github.com>
Date: Mon, 26 Jun 2023 23:21:04 +0100
Subject: [PATCH 2/3] `value_type&` -> `value_type const&`

  * "Non-const lvalue reference to type 'value_type' (aka 'int') cannot bind to a temporary of type 'int'"
  * simple fix making the lvalue reference const
---
 listings/listing_8.11.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/listings/listing_8.11.cpp b/listings/listing_8.11.cpp
index 7f53915..75709c3 100644
--- a/listings/listing_8.11.cpp
+++ b/listings/listing_8.11.cpp
@@ -24,7 +24,7 @@ void parallel_partial_sum(Iterator first,Iterator last)
                 std::partial_sum(begin,end,begin);
                 if(previous_end_value)
                 {
-                    value_type& addend=previous_end_value->get();
+                    value_type const& addend=previous_end_value->get();
                     *last+=addend;
                     if(end_value)
                     {

From 5fd95a34d155cbce3f06587a5410fff27217f11a Mon Sep 17 00:00:00 2001
From: ITHelpDec <34002836+ITHelpDec@users.noreply.github.com>
Date: Mon, 26 Jun 2023 23:29:18 +0100
Subject: [PATCH 3/3] complete `join_threads` class

  * "Thread 1: signal SIGABRT"
  * code will crash with current implementation
---
 listings/listing_8.11.cpp | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/listings/listing_8.11.cpp b/listings/listing_8.11.cpp
index 75709c3..3cd4b12 100644
--- a/listings/listing_8.11.cpp
+++ b/listings/listing_8.11.cpp
@@ -1,10 +1,20 @@
 #include <future>
 #include <algorithm>
 #include <vector>
-struct join_threads
-{
-    join_threads(std::vector<std::thread>&)
-    {}
+
+class join_threads {
+public:
+    join_threads(std::vector<std::thread> &threads) : threads_(threads) { }
+
+    ~join_threads()
+    {
+        for (auto &t : threads_) {
+            if (t.joinable()) { t.join(); }
+        }
+    }
+
+private:
+    std::vector<std::thread> &threads_;
 };
 
 template<typename Iterator>