C Interview Questions and Answers

 

I had a frustrating problem which turned out to be caused by the line

I had a frustrating problem which turned out to be caused by the line



printf("%d", n);



where n was actually a long int. I thought that ANSI function prototypes were supposed
to guard against argument type mismatches like this.





When a function accepts a variable number of arguments, its prototype does not (and
cannot) provide any information about the number and types of those variable arguments.
Therefore, the usual protections do not apply in the variable-length part of variable-length
argument lists: the compiler cannot perform implicit conversions or (in general)
warn about mismatches. The programmer must make sure that arguments match, or must
manually insert explicit casts.



In the case of printf-like functions, some compilers (including gcc) and some versions
of lint are able to check the actual arguments against the format string, as long
as the format string is an immediate string literal.

Posted by:Richards