UndefinedBehaviorSanitizer

#include <stdio.h>
#include <limits.h>

__attribute__((noinline)) int cong(int a, int b) { return a + b; }
__attribute__((noinline)) unsigned dich(unsigned x, int n) { return x << n; }
__attribute__((noinline)) int chia(int a, int b) { return a / b; }

int main(void) {
    printf("cong  = %d\n", cong(INT_MAX, 1));
    printf("dich  = %u\n", dich(1, 32));
    printf("chia  = %d\n", chia(10, 0));

    return 0;
}

/* 1. alignment: quan trong tren ARM, noi truy cap lech lam sap chuong trinh */

char bo_dem[16];
int *p = (int *)(bo_dem + 1);      /* lech 1 byte */
*p = 42;

/* UBSan: runtime error: store to misaligned address 0x... for type 'int',
   which requires 4 byte alignment */

/* 2. bounds: chi hoat dong khi kich thuoc BIET LUC DICH */

int a[5];
int i = doc_so();
a[i] = 1;                          /* UBSan bat neu i ngoai 0..4 */

int *b = malloc(5 * sizeof *b);
b[i] = 1;                          /* UBSan KHONG bat: kich thuoc khong biet.
                                      Cai nay la viec cua ASan. */

/* 3. return: bat duoc dung cho ma UB o Bai 33.2 */

int f(int x) { if (x) return 1; }

/* UBSan: runtime error: execution reached the end of a value-returning
   function without returning a value */

# 1. Tat ca cac kiem tra mac dinh
gcc -fsanitize=undefined prog.c

# 2. Chi mot vai nhom
gcc -fsanitize=signed-integer-overflow,shift,null prog.c

# 3. Tat ca tru mot nhom
gcc -fsanitize=undefined -fno-sanitize=alignment prog.c

# 4. Them nhom KHONG nam trong "undefined"
gcc -fsanitize=undefined,unsigned-integer-overflow prog.c

# Mac dinh: bao roi chay tiep
gcc -fsanitize=undefined prog.c

# Dung han o loi dau tien, va tra ve ma thoat khac 0
gcc -fsanitize=undefined -fno-sanitize-recover=all prog.c

# Hoac dat luc chay
UBSAN_OPTIONS=halt_on_error=1 ./prog

# In ca vet goi cho moi bao loi
UBSAN_OPTIONS=print_stacktrace=1 ./prog

gcc -std=c11 -g3 -O1 \
    -fno-omit-frame-pointer \
    -fsanitize=address,undefined \
    -fno-sanitize-recover=all \
    -Wall -Wextra \
    -o prog prog.c

# Hai sanitizer nay dung chung duoc, va nen dung chung.
# Chi phi cong lai van chi khoang 2.2 lan.

# KHONG dung chung voi thread:
gcc -fsanitize=address,thread prog.c
# error: -fsanitize=address is incompatible with -fsanitize=thread