Correct way to take absolute value of INT_MIN

Posted by aka.nice on Stack Overflow See other posts from Stack Overflow or by aka.nice
Published on 2012-09-01T21:29:52Z Indexed on 2012/09/01 21:38 UTC
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c

I want to perform some arithmetic in unsigned, and need to take absolute value of negative int, something like

do_some_arithmetic_in_unsigned_mode(int some_signed_value)
{
   unsigned int magnitude;
   int negative;
   if(some_signed_value<0) {
       magnitude = 0 - some_signed_value;
       negative = 1;
    } else {
       magnitude = some_signed_value;
       negative = 0;
    }
   ...snip...
}

But INT_MIN might be problematic, 0 - INT_MIN is UB if performed in signed arithmetic. What is a standard/robust/safe/efficient way to do this in C?

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