Protected the apparently racy glibc's backtrace (detected in an helgrind run on TeamCity).

castor/exception/Backtrace.cpp

@@ -31,7 +31,9 @@
 castor::exception::Backtrace::Backtrace(): m_trace() {
   void * array[200];
   size_t depth = ::backtrace(array, sizeof(array)/sizeof(void*));
+  g_lock.lock();
   char ** strings = ::backtrace_symbols(array, depth);
+  g_lock.unlock();
   if (!strings)
     m_trace = "";
   else {
@@ -66,3 +68,5 @@ castor::exception::Backtrace::Backtrace(): m_trace() {
   }
 }
 
+/* Implementation of the singleton lock */
+castor::exception::Backtrace::mutex castor::exception::Backtrace::g_lock;

castor/exception/Backtrace.hpp

@@ -23,6 +23,7 @@
 #pragma once
 
 #include <string>
+#include <pthread.h>
 
 namespace castor {
   namespace exception {
@@ -33,6 +34,20 @@ namespace castor {
       Backtrace& operator= (const Backtrace& bt) { m_trace = bt.m_trace; return *this; }
     private:
       std::string m_trace;
+      /**
+       * Singleton lock around the apparently racy backtrace().
+       * We write it with no error check as it's used only here.
+       * We need a class in order to have a constructor for the global object.
+       */
+      class mutex {
+      public:
+        mutex() { pthread_mutex_init(&m_mutex, NULL); }
+        void lock() { pthread_mutex_lock(&m_mutex); }
+        void unlock() { pthread_mutex_unlock(&m_mutex); }
+      private:
+        pthread_mutex_t m_mutex;    
+      };
+      static mutex g_lock;
     };
   }
 }