Free all memory allocated by malloc (), realloc () in C

Question

I am trying to free () all the allocated memory of malloc (), realloc (), but valgrind says it is a memory leak.

The code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>


int main(int argc, char *argv[]) {

    int lines_allocated = 128;
    int max_line_len = 50;

    FILE *fp;

    /* File allocate lines of text */
    char **array = (char **)malloc(sizeof(char*)*lines_allocated);
    if (array==NULL) {
        fprintf(stderr,"Out of memory (1).\n");
        exit(1);
    }

    FILE *file = fopen("file.txt", "r");
    if (file == NULL) {
        fprintf(stderr,"Error opening file.\n");
        exit(2);
    }

    int il;
    for (il = 0; 1; il++) {
        int j;

        /* Have we gone over our line allocation? */
        if (il >= lines_allocated) {
            int new_size;

            /* Double our allocation and re-allocate */
            new_size = lines_allocated*2;
            array = (char **)realloc(array,sizeof(char*)*new_size);

            if (array==NULL) {
                fprintf(stderr,"Out of memory.\n");
                exit(3);
            }

            lines_allocated = new_size;
        }

        /* Allocate space for the next line */
        array[il] = malloc(max_line_len);
        if (array[il]==NULL) {
                fprintf(stderr,"Out of memory (3).\n");
                exit(4);
            }
        if (fgets(array[il], max_line_len-1, file)==NULL)
            break;

        /* Get rid of CR or LF at end of line */
        for (j=strlen(array[il])-1;j>=0 && (array[il][j]=='\n' || array[il][j]=='\r');j--)
            ;

        array[il][j+1]='\0';
    }

    /* Close file */
    fclose(file);

    /* Print and free the every element of the array */
    int cc;
    for (cc = 0; cc < il; cc++) {
        printf("%s\n", array[cc]);

        /* Free the every element of the array */
        free(array[cc]);
    }

    /* Free hole array */
    free(array);

    return 0;
}

valgrind./main

valgrind --leak-check=full --show-reachable=yes ./main
==4806== Memcheck, a memory error detector
==4806== Copyright (C) 2002-2015, and GNU GPL'd, by Julian Seward et al.
==4806== Using Valgrind-3.11.0 and LibVEX; rerun with -h for copyright info
==4806== Command: ./main
==4806== 
1
2
3
4
5
6
7
8
9
10
11
==4806== 
==4806== HEAP SUMMARY:
==4806==     in use at exit: 50 bytes in 1 blocks
==4806==   total heap usage: 14 allocs, 13 frees, 2,192 bytes allocated
==4806== 
==4806== 50 bytes in 1 blocks are definitely lost in loss record 1 of 1
==4806==    at 0x4C2AC3D: malloc (vg_replace_malloc.c:299)
==4806==    by 0x40092E: main (in /var/www/mem/main)
==4806== 
==4806== LEAK SUMMARY:
==4806==    definitely lost: 50 bytes in 1 blocks
==4806==    indirectly lost: 0 bytes in 0 blocks
==4806==      possibly lost: 0 bytes in 0 blocks
==4806==    still reachable: 0 bytes in 0 blocks
==4806==         suppressed: 0 bytes in 0 blocks
==4806== 
==4806== For counts of detected and suppressed errors, rerun with: -v
==4806== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

How to free memory? It says that you need to free up another block of memory, but where is it?

Answer 1

for (cc = 0; cc < il; cc++) {

If ilis a valid index array(and it is), the comparison in the loop should be:

for (cc = 0; cc <= il; cc++) {

to invoke the very last element array(and free its memory).

Answer 2

Just replace

for (cc = 0; cc < il; cc++)

with

for (cc = 0; cc <= il; cc++)

, , , for (il = 0; 1; il++) . il++, il , for (cc = 0; cc < il; cc++) . , .

Answer 3

, il , fgets(array[il], max_line_len-1, file) NULL.

array[il] = malloc(max_line_len); NULL fgets . , , max_line_len.

// Check that we will need the allocation
char temp[max_line_len];
if (fgets(temp, max_line_len-1, file)==NULL) {
    break;
}
// Allocate only when we are sure that we are going to need it
temp[max_line_len-1] = '\0';
size_t len = strlen(temp);
array[il] = malloc(len+1);
if (array[il]==NULL) {
    fprintf(stderr,"Out of memory (3).\n");
    exit(4);
}

. realloc , . , exit(4), .

Answer 4

, , ( ), (, ), - - - . free() . - , - , free(), free().

( , ) :

malloc() .

_malloc(), malloc().

, , malloc() :

#define malloc( n )  ( *sp++ = _malloc( n ) )

, sp . : , malloc() . - , - free_all(), :

void free_all() {  
  while( --sp >= base_of_malloc_buf_stack ) {  
    free( *sp );   
    *sp = 0; /* avoid future re-free() */    
  }  
}