Is this valid

This is a discussion on Is this valid within the C Programming forums, part of the General Programming Boards category; Code: char str [] = "\"-d\""; sscanf( str , "\"%[^\"]", str ); I am not pretty sure, whether this is ...

  1. #1
    Registered User ssharish2005's Avatar
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    Is this valid

    Code:
    char str[] = "\"-d\"";
     
    sscanf(str, "\"%[^\"]", str);
    I am not pretty sure, whether this is legal or not. But it seems to compile fine with no error. The thing which i am worried about here is that, I am using the same char array "str" to point at fetched data again in sscanf. Is it right?

    Thank you

    sshairsh

  2. #2
    and the hat of wrongness Salem's Avatar
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    > I am using the same char array "str" to point at fetched data again in sscanf. Is it right?
    Yes, you're right to be worried, because it's wrong.

    Very few of the C standard library functions tolerate overlapping input and output data (memmove is one example which does). For pretty much everything else, assume undefined behaviour.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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  3. #3
    Registered User ssharish2005's Avatar
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    Quote Originally Posted by Salem View Post
    Very few of the C standard library functions tolerate overlapping input and output data (memmove is one example which does). For pretty much everything else, assume undefined behaviour.
    Salem, thanks a lot for that. I dint really knew about it. But I had a half mind saying that it wan't right. But now its all clear.

    ssharish

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