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vsprintf and others v...

Posted on 2000-05-17
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Last Modified: 2011-10-03
Here is my code:

va_list args;
char    traceText[10];

...

va_start (args, formatString);
vsprintf (&(traceText[sIndex]), formatString, args);
va_end(args);

...

Question1: Can you explain all the v... instructions in the code?
Question2: If relevant what is this part of code doing?
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Question by:pascal_lalonde
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2 Comments
 
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Accepted Solution

by:
imladris earned 50 total points
ID: 2817952
The va... instructions are macros for processing a variable list of arguments. The library function printf, for example, has one fixed argument (the format string) and a variable number of arguments after that.

To write such a function yourself you need information on those trailing unspecified arguments. The va... macros provide that support. A va_list contains the arguments. va_start initializes processing and va_end ends it.

In the code listed, the parameters are simply being passed through to vsprintf which will print the variable list of args into string tracetext according to the format in formatString.
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by:pascal_lalonde
ID: 2818806
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