Stack Vs Heap

Stack variables are automatic local objects, while heap objects are requested and released explicitly.

stack value `stackValue` is a normal local variable with automatic lifetime.

heap value `malloc` creates heap storage that must later be released with `free`.

                            stackValue
                            stackValue = 4 (default)stackValue = 7stackValue = 10
                        

                            stack_vs_heap.c
                        
Replay: real traced execution (multi-file project)

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

int main(void) {
    int stackValue = 4;
    int *heapValue = (int *)malloc(sizeof(int));

    if (heapValue == 0) {
        return 1;
    }

    *heapValue = stackValue + 1;

    printf("stack=%d heap=%d\n", stackValue, *heapValue);
    free(heapValue);
    return 0;
}
#include <stdio.h>
#include <stdlib.h>

int main(void) {
    int stackValue = 7;
    int *heapValue = (int *)malloc(sizeof(int));

    if (heapValue == 0) {
        return 1;
    }

    *heapValue = stackValue + 1;

    printf("stack=%d heap=%d\n", stackValue, *heapValue);
    free(heapValue);
    return 0;
}
#include <stdio.h>
#include <stdlib.h>

int main(void) {
    int stackValue = 10;
    int *heapValue = (int *)malloc(sizeof(int));

    if (heapValue == 0) {
        return 1;
    }

    *heapValue = stackValue + 1;

    printf("stack=%d heap=%d\n", stackValue, *heapValue);
    free(heapValue);
    return 0;
}

                        
1stackValue ← 4, heapValue ← ⟨addr A⟩⋯4int main(void) {5    int stackValue→ 4 = 4; //@stackValue=7, 106    int *heapValue→ ⟨addr A⟩ = (int *)malloc(sizeof(int));78    if (heapValue == 0) {9        return 1;10    }1112    *heapValue⟨addr A⟩ = stackValue4 + 1;1314    printf("stack=%d heap=%d\n", stackValue4, *heapValue⟨addr A⟩);15    free(heapValue⟨addr A⟩);16    return 0;17}⋯outputstack=4 heap=5
1stackValue ← 7, heapValue ← ⟨addr A⟩⋯4int main(void) {5    int stackValue→ 7 = 7;6    int *heapValue→ ⟨addr A⟩ = (int *)malloc(sizeof(int));78    if (heapValue == 0) {9        return 1;10    }1112    *heapValue⟨addr A⟩ = stackValue7 + 1;1314    printf("stack=%d heap=%d\n", stackValue7, *heapValue⟨addr A⟩);15    free(heapValue⟨addr A⟩);16    return 0;17}⋯outputstack=7 heap=8
1stackValue ← 10, heapValue ← ⟨addr A⟩⋯4int main(void) {5    int stackValue→ 10 = 10;6    int *heapValue→ ⟨addr A⟩ = (int *)malloc(sizeof(int));78    if (heapValue == 0) {9        return 1;10    }1112    *heapValue⟨addr A⟩ = stackValue10 + 1;1314    printf("stack=%d heap=%d\n", stackValue10, *heapValue⟨addr A⟩);15    free(heapValue⟨addr A⟩);16    return 0;17}⋯outputstack=10 heap=11