pivotal-jbarrett commented on a change in pull request #731:
URL: https://github.com/apache/geode-native/pull/731#discussion_r565524041
##########
File path: cppcache/src/TXId.cpp
##########
@@ -27,15 +27,27 @@ namespace apache {
namespace geode {
namespace client {
-std::atomic<int32_t> TXId::m_transactionId(1);
+std::atomic<int32_t> TXId::m_transactionId(0);
-TXId::TXId() : m_TXId(m_transactionId++) {}
+TXId::TXId() {
+ // If m_transactionId has reached maximum value, then set
+ // it to zero in order to avoid overflow to negative value.
+ auto maxValueTXId = INT32_MAX;
Review comment:
```c++
auto maxValueTXId = std::numeric_limits<int>::max();
```
https://en.cppreference.com/w/cpp/types/numeric_limits
##########
File path: cppcache/src/TXId.cpp
##########
@@ -27,15 +27,27 @@ namespace apache {
namespace geode {
namespace client {
-std::atomic<int32_t> TXId::m_transactionId(1);
+std::atomic<int32_t> TXId::m_transactionId(0);
-TXId::TXId() : m_TXId(m_transactionId++) {}
+TXId::TXId() {
+ // If m_transactionId has reached maximum value, then set
+ // it to zero in order to avoid overflow to negative value.
+ auto maxValueTXId = INT32_MAX;
+ m_transactionId.compare_exchange_strong(maxValueTXId, 0);
+ m_TXId = ++m_transactionId;
Review comment:
While highly unlikely it is possible for `m_transactionId` to be at max
value again between lines 36 and 37. This whole operation should be done in a
loop where you fetch the current, increment if less than max or reset to 0,
then compare and set the new value. If failure to set, then try again.
```c++
auto current = m_transactionId.load();
decltype(current) next;
do {
next = std::numeric_limits<decltype(current)>::max() == current ? 1 :
current + 1;
} while(!m_transactionId.compare_exchange_strong(current, next));
m_TXId = next;
```
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