Question

char* ReadNumericFormat = "%i";
int Read(void)
{
    int Storage;
    __asm
    {
        LEA    EAX, [Storage]
        PUSH   EAX
        PUSH   DWORD PTR [ReadNumericFormat]
        CALL   DWORD PTR [scanf]
        ADD    ESP, 8
        MOV    EAX, DWORD PTR [Storage]
    }     
}

when the user enters “023919” the procedure returns 19.
this is a feature or darkness is a standard?

Answer 1

Actually that’s because you’ve entered an octal number.

In C, numbers starting with 0 will be interpreted as octal (base-8) literals. Hence, in your input

023919

scanf find a leading zero without an x following, so assumes it’s an octal number. Then it consumes 2 and 3, until 9 which is not a valid octal digit and stop. So scanf now has

023

which is

2*8 + 3 = 19

So the procedure returns 19.

---

Use the format %d instead of %i to prevent this.