写入大小无效4

Question

这是有问题的代码:

long number = atol(argv[1]);
long prime_limit = number / 2;
int * primes = malloc(sizeof(int) * prime_limit);
long i;
for (i = 2; i <= prime_limit; i++) {
    primes[i] = 1; # This is line 16
}

以下是错误:

==9318== Invalid write of size 4
==9318==    at 0x40065B: main (003.c:16)
==9318==  Address 0x8 is not stack'd, malloc'd or (recently) free'd
==9318== 
==9318== 
==9318== Process terminating with default action of signal 11 (SIGSEGV)
==9318==  Access not within mapped region at address 0x8
==9318==    at 0x40065B: main (003.c:16)
==9318==  If you believe this happened as a result of a stack
==9318==  overflow in your program's main thread (unlikely but
==9318==  possible), you can try to increase the size of the
==9318==  main thread stack using the --main-stacksize= flag.
==9318==  The main thread stack size used in this run was 8388608.

我相信错误必须是我使用malloc的方式,但我不太确定.argv [1]的值是600851475143.

Answer 1

数组0在C中是-origin:

i <= prime_limit;

应该

i < prime_limit;

否则atol不安全,不能进行错误检测.使用strtol一个字符串转换为long.