7_1.c

#include<tlpi_hdr.h>

#define MAX_ALLOCS 1000000

int main(int argc, char *argv[]) {
    char *ptr[MAX_ALLOCS];
    int freeStep, freeMin, freeMax, blockSize, numAllocs;

    printf("\n");

    if (argc < 3 || strcmp(argv[1], "--help") == 0){
        usageErr("%s num-allocs block-size [step [min [max]]]\n", argv[0]);
    }

    numAllocs = getInt(argv[1], GN_GT_0, "num-allocs");

    if (numAllocs > MAX_ALLOCS) {
        cmdLineErr("num-allocs should not larger than %d\n", MAX_ALLOCS);
    }

    blockSize = getInt(argv[2], GN_GT_0 | GN_ANY_BASE, "block-size");

    freeStep = (argc > 3) ? getInt(argv[3], GN_GT_0, "step") : 1;
    freeMin = (argc > 4) ? getInt(argv[4], GN_GT_0, "min") : 1;
    freeMax = (argc > 5) ? getInt(argv[5], GN_GT_0, "max") : numAllocs;

    if (freeMax > numAllocs) {
        cmdLineErr("free-max should not larger than num-allocs\n");
    }

    printf("Initial program break;    %10p\n", sbrk(0));

    printf("Allocating %d * %d bytes \n", numAllocs, blockSize);

    for (int i = 1; i <= numAllocs; i ++) {
        ptr[i] = malloc(blockSize);
        if (ptr[i] == NULL) {
            errExit("malloc");
        }
        printf("Allocating %d * %d bytes, the program break is now:    %10p\n", i, blockSize, sbrk(0));
    }

    printf("Program break is now:    %10p\n", sbrk(0));

    printf("Freeing blocks from %d to %d in steps of %d\n", freeMin, freeMax, freeStep);
    for (int i = freeMin; i < freeMax; i+=freeStep) {
        free(ptr[i]);
    }
    printf("After free(), the program break is now:    %10p\n", sbrk(0));
    
    exit(EXIT_SUCCESS);
}