Exercising _FORTIFY_SOURCE in gcc (clang should work as well)

fortify.c

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

/*
 * Simple test program for FORTIFY_SOURCE.
 *
 * Compile with the following to test with no source fortification and stack protection off:
 * gcc -D_FORTIFY_SOURCE=0 -fno-stack-protector fortify.c -o fortify
 *
 * Then try different values for FORTIFY_SOURCE (1-3) and -fstack-protector to enable stack protection.
 */
void memsetOverflow(int b) {

    printf("Memset Overflow\n");
    char small_buf[8];
    char *sbp = small_buf;
    if (b) {
	sbp = malloc(23);
    }
    memset(sbp, 0, 22);
    printf("%s\n", sbp);
    printf("Memset Overflow End\n");
}

void overflowStruct() {

    printf("%s\n", "Overflow Struct Test");
    char large_input[] = "MoreTextThanBuffer";
    struct outerStruct {
	struct innerStruct {
	    char buf[4];
	    int n;
	} inner;
	char buf[20];
    };
    struct outerStruct test_struct;
    strcpy(test_struct.inner.buf, large_input);
    printf("%s\n", test_struct.inner.buf);
    printf("%s\n", "Overflow Struct Test End");
}

void overflowBuffer() {

    printf("Simple Buffer Overflow\n");
    char large_input[] = "MoreTextThanBuffer";
    char small_buf[8];
    strcpy(small_buf, large_input);
    printf("%s\n", small_buf);
    printf("Simple Buffer Overflow Test End\n");
}

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

    printf("Exercising my buffers\n");
    memsetOverflow(0);
    overflowStruct();
    overflowBuffer();

    printf("My buffers hurt\n");
    return 0;
}