Added some locking to the linux curl networking code

modules/juce_core/native/juce_curl_Network.cpp

@@ -46,6 +46,7 @@ struct CURLSymbols
         std::unique_ptr<CURLSymbols> symbols (new CURLSymbols);
 
        #if JUCE_LOAD_CURL_SYMBOLS_LAZILY
+        const ScopedLock sl (getLibcurlLock());
         #define JUCE_INIT_CURL_SYMBOL(name)  if (! symbols->loadSymbol (symbols->name, #name)) return nullptr;
        #else
         #define JUCE_INIT_CURL_SYMBOL(name)  symbols->name = ::name;
@@ -70,6 +71,14 @@ struct CURLSymbols
         return symbols;
     }
 
+    // liburl's curl_multi_init calls curl_global_init which is not thread safe
+    // so we need to get a lock during calls to curl_multi_init and curl_multi_cleanup
+    static CriticalSection& getLibcurlLock() noexcept
+    {
+        static CriticalSection cs;
+        return cs;
+    }
+
 private:
     CURLSymbols() = default;
 
@@ -105,7 +114,10 @@ public:
     {
         jassert (symbols); // Unable to load libcurl!
 
-        multi = symbols->curl_multi_init();
+        {
+            const ScopedLock sl (CURLSymbols::getLibcurlLock());
+            multi = symbols->curl_multi_init();
+        }
 
         if (multi != nullptr)
         {
@@ -175,6 +187,7 @@ public:
     void cleanup()
     {
         const ScopedLock lock (cleanupLock);
+        const ScopedLock sl (CURLSymbols::getLibcurlLock());
 
         if (curl != nullptr)
         {