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???
10/15/08 12:06
Modified:
  10/15/08 12:08

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#159079 - Wrong!
Responding to: ???'s previous message
By definition, ':', '\t', '\r' and '\n' are always one character large (but may be multiple bytes on a compiler running wide character sets). That is a known.

But your assumptions about the produced number of characters when printing numbers is based on an incorrect assumption.

%4d is four characters large if and only if the value to print can fit in four characters. The value -1000 requires five characters. The value 12345 also requires five characters. printf() will not throw away extra characters to produce a lie. It will extend the field width and emit every required character!

That is why you should never (N.E.V.E.R.) manually "count" the number of produced characters. In this case, you may write a broken record to a flash file system, or send a broken packet on a communication board. But this world is full of programs with dangerous buffer-overflow vulnerabilities, costing many millions of dollars every hour, just because people have assumed that they knew the size of the output from the *printf() family of functions.

List of 17 messages in thread
TopicAuthorDate
How many bytes will be written ??            01/01/70 00:00      
   return value?            01/01/70 00:00      
      OT: That's why you should never use TABs!            01/01/70 00:00      
         go ahead and use tabs            01/01/70 00:00      
            No, don't!            01/01/70 00:00      
            Any programmers editor            01/01/70 00:00      
               insert spaces for TABs            01/01/70 00:00      
      Oh Yes ... the sprintf()...            01/01/70 00:00      
         So here we go            01/01/70 00:00      
            Wrong!            01/01/70 00:00      
               Valid warnings. But...            01/01/70 00:00      
                  No buts!            01/01/70 00:00      
                     maintability and engineering            01/01/70 00:00      
               Not entirely true?            01/01/70 00:00      
                  You are correct            01/01/70 00:00      
                     Good example of counting dangers            01/01/70 00:00      
                        Good interaction.            01/01/70 00:00      

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