Question

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Pass a buffer by reference to other function

When I call the function ast It saves data on buffer and in bufferlen, but I try to access this pointer from dec and I can print *bufferlen but *buffer it´s impossible.

When I do temp=buffer a segmentation fault appears.And in the debugger I see in buffer “Address 0x7f out of bounds”. How can I print buffer from dec?? Which is the error?

  void ast(KOCTET *buffer,KUINT16 *bufferlen){
        KOCTET  *Bufferencode,*temp;
        KUINT16 BufferSize=5000;
        KUINT16 WritePos=0;
        KUINT16 total_bytes;
        Bufferencode=(KOCTET*)malloc(5000*sizeof(KOCTET));
        memset(Bufferencode,0,sizeof(Bufferencode));

        total_bytes = stream.CopyIntoBuffer( Bufferencode, BufferSize, WritePos);

        buffer=Bufferencode;
        *bufferlen=total_bytes;

        int z=0;
        temp=buffer;
        while (z<(*bufferlen)){
           printf(" %02X",(unsigned char)*temp);
           temp++;
           z++;
        }
        printf("\n");

    }


    void dec()
    {
       KOCTET *buffer,*temp;
       KUINT16 *bufferlen;

       ast_process_048(buffer,bufferlen);


       int z=0;
       temp=buffer;
       while (z<(*bufferlen)){
         printf(" %02X",(unsigned char)*temp);
         temp++;
         z++;
       }
       printf("\n");

    }

Answer 1

There are several problems with your code.

1. Within ast you access *bufferlen several times, without having memory allocated to it before.

2. I suppose you want to hand over the memory allocated for Bufferencode to buffer for further use outside ast with your statement buffer=Bufferencode; . However, this would require:

   void ast(KOCTET **buffer, ...)
   {
       ...
       *buffer = Bufferencode;
       ...
   }
   
   void dec()
   {
       KOCTET *buffer;
       ...
       ast_process_048(&buffer,...);
       ...
   }
   

These are just the first obvious problems – there might be more. Consider the suggestions in the answer to your yesterday’s question and – maybe – learn a bit more about basic C programming and pointer handling at all.