Static initialization order issue fix (#33)

* Use function-local static variables to eliminate the static initialization order issues.

* bump version to 4.0.4

include/configcat/configcatclient.h

@@ -146,8 +146,15 @@ class ConfigCatClient {
     std::shared_ptr<OverrideDataSource> overrideDataSource;
     std::unique_ptr<ConfigService> configService;
 
-    static std::mutex instancesMutex;
-    static std::unordered_map<std::string, std::shared_ptr<ConfigCatClient>> instances;
+    static inline std::mutex& getInstancesMutex() {
+        static std::mutex instancesMutex;
+        return instancesMutex;
+    }
+
+    static inline std::unordered_map<std::string, std::shared_ptr<ConfigCatClient>>& getInstances() {
+        static std::unordered_map<std::string, std::shared_ptr<ConfigCatClient>> instances;
+        return instances;
+    }
 };
 
 } // namespace configcat

src/configcatclient.cpp

@@ -17,9 +17,6 @@ using namespace std::chrono;
 
 namespace configcat {
 
-std::mutex ConfigCatClient::instancesMutex;
-std::unordered_map<std::string, std::shared_ptr<ConfigCatClient>> ConfigCatClient::instances;
-
 bool isValidSdkKey(const string& sdkKey, bool customBaseUrl) {
     static constexpr char proxyPrefix[] = "configcat-proxy/";
 
@@ -53,7 +50,8 @@ std::shared_ptr<ConfigCatClient> ConfigCatClient::get(const std::string& sdkKey,
         }
     }
 
-    lock_guard<mutex> lock(instancesMutex);
+    lock_guard<mutex> lock(getInstancesMutex());
+    auto& instances = getInstances();
     auto client = instances.find(sdkKey);
     if (client == instances.end()) {
         client = instances.insert({sdkKey, make_shared<ConfigCatClient::MakeSharedEnabler>(sdkKey, actualOptions)}).first;
@@ -72,7 +70,8 @@ void ConfigCatClient::close(const std::shared_ptr<ConfigCatClient>& client) {
     }
 
     {
-        lock_guard<mutex> lock(instancesMutex);
+        lock_guard<mutex> lock(getInstancesMutex());
+        auto& instances = getInstances();
 
         client->closeResources();
 
@@ -89,7 +88,8 @@ void ConfigCatClient::close(const std::shared_ptr<ConfigCatClient>& client) {
 }
 
 void ConfigCatClient::closeAll() {
-    lock_guard<mutex> lock(instancesMutex);
+    lock_guard<mutex> lock(getInstancesMutex());
+    auto& instances = getInstances();
 
     for (const auto& [_, instance] : instances) {
         instance->closeResources();
@@ -99,7 +99,8 @@ void ConfigCatClient::closeAll() {
 }
 
 size_t ConfigCatClient::instanceCount() {
-    lock_guard<mutex> lock(instancesMutex);
+    lock_guard<mutex> lock(getInstancesMutex());
+    auto& instances = getInstances();
 
     return instances.size();
 }

src/version.h

@@ -1,3 +1,3 @@
 #pragma once
 
-#define CONFIGCAT_VERSION "4.0.3"
+#define CONFIGCAT_VERSION "4.0.4"