need const char * anyway

passphrase_cache.cc

@@ -45,7 +45,7 @@ namespace pEp {
         _cache.splice(_cache.end(), _cache, entry);
     }
 
-    std::string PassphraseCache::latest_passphrase()
+    const char *PassphraseCache::latest_passphrase()
     {
         std::lock_guard<std::mutex> lock(_mtx);
         
@@ -58,7 +58,7 @@ namespace pEp {
         }
 
         --_which;
-        return _which->passphrase;
+        return _which->passphrase.c_str();
     }
 };
 

passphrase_cache.hh

@@ -56,7 +56,7 @@ namespace pEp {
         // this function is throwing std::underflow_error when no passphrases
         // are left
 
-        std::string latest_passphrase();
+        const char *latest_passphrase();
 
         // convenience functions
         // i.e.