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From: Malcolm McLean <malcolm.arthur.mclean@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: "undefined behavior"?
Date: Thu, 13 Jun 2024 05:47:57 +0100
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On 13/06/2024 01:33, Keith Thompson wrote:
>
> printf is a variadic function, so the types of the arguments after
> the format string are not specified in its declaration.  The printf
> function has to *assume* that arguments have the types specified
> by the format string.  This:
>      printf("%d\n", foo);
> (probably) has undefined behavior if foo is of type size_t.
 >
And isn't that a nightmare?
> There is no implicit conversion to the expected type.  Note that
> the format string doesn't have to be a string literal, so it's
> not always even possible for the compiler to check the types.
> Variadic functions give you a lot of flexibility at the cost of
> making some type errors difficult to detect.
> 
> (I wrote "probably" because size_t *might* be a typedef for unsigned
> int, and there are special rules about arguments of corresponding
> signed and unsigned types.)
> 

We just can't have size_t variables swilling around in prgrams for these 
reasons.
-- 
Check out my hobby project.
http://malcolmmclean.github.io/babyxrc