Question

I keep getting a debug assertion failed error and I can’t figure out why. I get the error when this code is ran:

     private: System::Void txtMessage_KeyDown(System::Object^ sender, System::Windows::Forms::KeyEventArgs^  e) {
         if(e->KeyCode == Keys::Enter && txtMessage->Text != ""){

             char* MESSAGE = new char[txtMessage->Text->Length];
             ZeroMemory(MESSAGE, sizeof(MESSAGE));

             string strMESSAGE = "";

             MarshalString(txtMessage->Text, strMESSAGE);
             memcpy(MESSAGE, strMESSAGE.c_str(), sizeof(strMESSAGE));

             if (send(sConnect, MESSAGE, 256, NULL) != SOCKET_ERROR){
                 txtMessage->Clear();
             }
         }
     }

Sometimes the error doesn’t occur until after I use that code multiple times and sometimes I get it the first time I use it. I really don’t know why I am getting this and, I can’t figure out how to fix it. So if anyone can help I would appreciate it.

The error I keep getting during that code is:

Answer 1

This is incorrect:

char* MESSAGE = new char[txtMessage->Text->Length];
ZeroMemory(MESSAGE, sizeof(MESSAGE));

as it will only zeroise sizeof(char*) bytes instead of intended Length.

The allocation for MESSAGE is also based on txtMessage but is written to from strMessage. It may be the case that the lengths of these string objects are not equal, possibly resulting in allocating insufficient memory.

The use of memcpy() is also incorrect:

memcpy(MESSAGE, strMESSAGE.c_str(), sizeof(strMESSAGE));

as sizeof(strMESSAGE) is not the number of characters in strMESSAGE. Use length() instead.

The call to send() will also be attempting to access 256 characters from MESSAGE which may be greater than that allocated for MESSAGE resulting accessing memory it should not.

I am unsure why the call send() is not simply:

if (send(sConnect,strMESSAGE.c_str(),strMESSAGE.length(), NULL) != SOCKET_ERROR){

avoiding any dynamic memory allocation or copying.

Just to note I am unfamiliar with MarshalString() so cannot comment on its use.