5 Replies Latest reply on Oct 24, 2016 3:57 PM by Intel Corporation

    Edison malloc problem?

    Aravind_Sridhar

      I'm trying to test the UART code on the Edison from the mraa library. As a part of the code, I'm declaring a character array and mallocing it. However, something weird is happening.

      No matter what size I try to malloc, the size of the array is returned by the sizeof() function is always 4. I don't know if this is a problem with memory management by the kernel or if something is wrong with the sizeof() function.

          /*
           * Author: Thomas Ingleby <thomas.c.ingleby@intel.com>
           * Author: Brendan Le Foll <brendan.le.foll@intel.com>
           * Copyright (c) 2014, 2015 Intel Corporation.
           *
           * Permission is hereby granted, free of charge, to any person obtaining
           * a copy of this software and associated documentation files (the
           * "Software"), to deal in the Software without restriction, including
           * without limitation the rights to use, copy, modify, merge, publish,
           * distribute, sublicense, and/or sell copies of the Software, and to
           * permit persons to whom the Software is furnished to do so, subject to
           * the following conditions:
           *
           * The above copyright notice and this permission notice shall be
           * included in all copies or substantial portions of the Software.
           *
           * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
           * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
           * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
           * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
           * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
           * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
           * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
           */
      
      
          #include "stdio.h"
          #include "mraa.h"
          #include <string.h>
          #define num_char 7
      
      
      
      
          int main(int argc, char** argv)
          {
              mraa_uart_context uart;
              uart = mraa_uart_init(0);
              mraa_uart_set_baudrate(uart,9600);
      
      
              if (uart == NULL) {
                  fprintf(stderr, "UART failed to setup\n");
                  return EXIT_FAILURE;
              }
      
      
              char* buffer;
      
      
              buffer = (char*)(malloc(num_char));
              
              //memset(buffer, '\0', sizeof(buffer));
              
              printf("Size:%d\n",sizeof(buffer));
              
              /*while(1)
              {   
                  mraa_uart_write(uart,"a",1);
      
      
                  mraa_uart_read(uart, buffer, num_char);
      
      
                  printf("%s\n",buffer);
      
      
                  sleep(1);
              }*/
              
              
      
      
              mraa_uart_stop(uart);
      
      
              mraa_deinit();
      
      
              return EXIT_SUCCESS;
          }
      

       

      Thanks in advance,

      Aravind

        • 1. Re: Edison malloc problem?
          Intel Corporation
          This message was posted on behalf of Intel Corporation

          Hi Aravind,

           

          Thank you for contacting us!

           

          It seems to be related to how you are using the function sizeof(), in this case you are printing the size of the pointer (char * buffer), so, that will be 4. I’d suggest you try these:

           

          Char * buffer;                                                       //to declare a pointer
          buffer = (char*) malloc(num_char);                         //Reserve the quantity of memory (bytes) specified by num_char
          if (buffer == NULL){                                              //check if the memory was reserved
                      printf(“The memory hasn’t been reserved”);
          }
          printf(“Pointer address: %d \n”, bufffer);                //print the address of the memory location
          printf(“Memory contain: %d \n“, *buffer)                //print the contained in the memory
          

           

          Hope this information helps, if you need more help, please let me know.

           

          Regards,
          -Yermi

          • 2. Re: Edison malloc problem?
            Intel Corporation
            This message was posted on behalf of Intel Corporation

            Hi Aravind,

             

            I would like to know if you have tried my previous suggestions. If you need more assistance, please let me know.

             

            Regards,
            -Yermi

            • 3. Re: Edison malloc problem?
              Aravind_Sridhar

              Hi Yermi,

              I haven't had time to test it out yet. I'll post the result on this thread once I'm able to.

              Thanks,

              Aravind

              • 4. Re: Edison malloc problem?
                Intel Corporation
                This message was posted on behalf of Intel Corporation

                Hi Aravind,

                Great! We’ll be waiting for you. Have a nice day!

                Regards,
                -Yermi
                 

                • 5. Re: Edison malloc problem?
                  Intel Corporation
                  This message was posted on behalf of Intel Corporation

                  Hi Aravind,

                   

                  We would like to know if you have had time to test it, and also, if you need more help, please let us know.

                   

                  Regards,
                  -Yermi