Re: [libmicrohttpd] MHD_RESPMEM_PERSISTENT

[Miguel Sancho]

Hi Silvio, thanks for answering,

> Could you show what error and how the buffer was assigned?

The error is that the downloaded binary file from the MHD server with the MHD_RESPMEM_PERSISTENT option is corrupt:

• Same size as the original
• The initial bytes are ok
  
• but from a certain point file contents are set to '0'. The free(buffer) seems to impact the content downloaded in the http response, I do not how because free() is after the MHD_destroy_response()
• Buffer is correctly downloaded when using the MHD_RESPMEM_MUST_COPY option but I wanted to minimize the memory impacts
  

The buffer is allocated by the MHD server with malloc, simplifying:
             unsigned char* buffer = (unsigned char*)malloc(dataSize);
             memcpy(buffer, data, dataSize);

Another thing I observe is that if I remove the free(buffer), the file is correctly downloaded. However this solution is not valid because in this case I have a memory leak:

            response = MHD_create_response_from_buffer(
                                 size,(void*)buffer,MHD_RESPMEM_PERSISTENT);
            ret = MHD_queue_response (connection, 200, response);       
            MHD_destroy_response (response);
            //free(buffer);   // Memory Leak!

Thanks

Miguel