malloc

[zaoqi]

malloc is not declared in current scope

[dawsonjon]

Hi, Thanks very much for the feedback. Please could you expand a little? What steps should I take to reproduce the problem?

[zaoqi]

http://dawsonjon.pythonanywhere.com/

/*LZSS Compression Component*/
/*Jonathan P Dawson 2014-07.10*/
  /* diff */
#include <stdlib.h>                    
const int N = 1024;
const int LOG2N = 10;

unsigned raw_in = input("raw_in");
unsigned compressed_out = output("compressed_out");

/*Create a to send data of an arbitrary bit length*/
unsigned packed, stored = 0;
void send_bits(unsigned data, unsigned bits){
    unsigned i;
    for(i=0; i<bits; i++){
        packed >>= 1;
        packed |= (data & 1) << 31;
        data >>= 1;
        stored++;
        if(stored == 32){
            fputc(packed, compressed_out);
            stored = 0;
        }
    }
}

/*A function that reads a stream of uncompressed data, 
and creates a stream of compressed data*/

void compress(){
    malloc(1);           /* diff */
  
    unsigned pointer, match, match_length, longest_match, longest_match_length;
    unsigned buffer[N];

    unsigned new_size;

    while(1){
        for(pointer=0; pointer<N; pointer++){
            buffer[pointer] = fgetc(raw_in);
        }

        pointer=0;
        new_size = 0;
        while(pointer<N){

            /*Find the longest matching string already sent*/
            longest_match = 0;
            longest_match_length = 0;
            for(match=0; match<pointer; match++){

                /*match length of 0 indicates no match*/
                match_length = 0;

                /*search through buffer to find a match*/
                while(buffer[match+match_length] == buffer[pointer+match_length]){
                    match_length++;
                }

                /*If this is the longest match, remember it*/
                if(match_length > longest_match_length){
                    longest_match = match;
                    longest_match_length = match_length;
                }

            }

            /*send data*/
            if(longest_match_length >= 3){
                send_bits(0, 1);
                send_bits(longest_match_length, LOG2N);
                send_bits(pointer - longest_match, LOG2N);
                pointer += longest_match_length;
                new_size += LOG2N + LOG2N + 1;
            }
            else{
                send_bits(1, 1);
                send_bits(buffer[pointer], 8);
                pointer++;
                new_size += 9;
            }

        }
    }
}

[zaoqi]

Error in file: /home/dawsonjon/main.c at line: 31
malloc is not declared in current scope

[zaoqi]

@dawsonjon

[dawsonjon]

Hi,

Dynamic memory allocation is a fairly experimental feature, but I have done a couple of fixes and I think it is working now. You need to define a couple of macros to get it working. The first enables dynamic memory allocation, and the second determines the amount of memory to reserve for dynamic allocation.

Thanks
Jon

#define ENABLE_DYNAMIC_MEMORY
#define MALLOC_SIZE 1024
#include <stdlib.h>
void main(){

int * a;
a = malloc(1);
free(a);

}