Progressively request memory up to the specified GB (e.g. "./memtest 5" will try allocate up to 5 GB of memory).

memtest.c

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

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

	// Check input arguments.
	if(argc<=1) {
		printf("Please provide the maximum number of GB to allocate, e.g.: ./memtest 5");
		exit(1);
	}
	int max_gb;
	max_gb = atoi(argv[1]);  // Convert input argument to integer.
	printf("Requesting 1 GB chunks up to %d GB.\n", max_gb);

	// Initialise vars.	
    int* arr;
    int iter_gb, cur_gb, i, n, j;
    iter_gb = 1;
    n = (1000000000 * iter_gb) / sizeof(int);  // number of elements to be iter_gb.

    // Initialise the pointer by allocating a small amount of memory.
    arr = (int*)malloc(sizeof(int));
    if (arr == NULL) {
    	printf("ERROR: Unable to initialise the array.\n");
    	exit(1);
    }

    // Keep requesting memory up to max_gb.
    for(i = 0; i < max_gb; ++i) {
    	printf(" INFO: Memory requested (%d/%d) GB... requesting memory...", i * iter_gb, max_gb);
    	arr = realloc(arr, n * (i + 1) * sizeof(int));
    	if (arr == NULL) {
    		printf("\nERROR: Unable to request more memory (failed at %d GB).\n", i * iter_gb);
    		exit(1);
    	}
    	// Initialise the elements of the array.
    	printf(" initialising...");
    	for (j = 0; j < n * (i + 1); ++j) {
    		arr[j] = j;
    	}
    	printf(" done!\n");
    }

    // Done.
    printf(" DONE: Successfully allocated %d GB of memory.\n", max_gb);
    free(arr);
    return 0;
}