运行时检查失败＃2-变量“ z”周围的堆栈已损坏

Question

I have this code:

 char z[9]; Int_To_BCD(vInt, z); Buflen += sprintf(BufStr + Buflen, "(%s)", z); 

And:

void Int_To_BCD (int val, char *out) {

  int i = 0; int j = 0; int outIndex = 0; unsigned char digits[4]; unsigned char Digit[2]; memcpy((void*)digits, (void*)&val, 4); for (i = 0; i <= 3; i++) { Digit[0] = (digits[i] & HIGH) / 16; Digit[1] = digits[i] & LOW; for (j = 0; j < 2; j++) { sprintf(&(out[outIndex]), "%d", Digit[j]); outIndex++; } } if (outIndex == 0) { sprintf(&(out[outIndex]), "%d", 0); outIndex++; } out[outIndex] = '\\0'; } 

In debug mode: the program run until the end of the main function and show the message:

Run-Time Check Failure #2 - Stack around the variable 'z' was corrupted

the maximun of outIndex is 8 always. and z has 8 bytes of memory. hasn't it?

What is the problem?

Thanks!

Answer 1

Here you seem to take upper and lower half of the byte.

Digit[0] = (digits[i] & HIGH) / 16;
Digit[1] = digits[i] & LOW;

These are hex digits: they range from 0-15.

This means that if the last digit is greater than 9, sprintf with %d will print 3 characters (2 digits and \\0 ) and you will have a buffer overflow.

Answer 2

Use %c instead of %d in

sprintf(&(out[outIndex]), "%d", Digit[j]);

is it working well?