Using sprintf will change the specified variable

Question

I have a code,

char* bin2hexchar( const unsigned char& ibin, char* pbcd )
{
    sprintf( pbcd, "%02X", ibin );

    return pbcd;
}

The problem is, the value of ibin variable will change to zero value.

Please advice.

Thanks

This is not C code, as ibin is a reference.

Matt Joiner
– Matt Joiner

2010-09-14 04:13:53 +00:00
Commented Sep 14, 2010 at 4:13 — Matt Joiner
– Matt Joiner, Commented Sep 14, 2010 at 4:13

paxdiablo · Accepted Answer · 2010-09-14 04:14:43Z

13

If your ibin is changing to a zero value in the caller to this function, the most likely explanation is buffer overflow.

I suspect it's probably because the buffer you're passing in as the second argument is defined thus:

char buff[2];

and ibin is adjacent to it on the stack.

The %02X format string requires three bytes, two for the characters and one for the terminating NUL character.

Even if that's not the specific case, it's still almost certainly buffer overflow. If so, please post the code that calls this function, along with the definitions for the relevant variables.

answered Sep 14, 2010 at 4:14

paxdiablo

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