Re: "undefined behavior"?

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.
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