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From: nobody@example.org (Scott)
Newsgroups: comp.lang.c
Subject: Re: is there a way to ask a variable what it is?
Date: Thu, 30 Jan 2020 15:59:55 GMT
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On Wed, 29 Jan 2020 20:58:47 +0000, Bart <bc@freeuk.com> wrote:

>On 29/01/2020 20:49, Stefan Ram wrote:
>> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>>> Let me illustrate.  If knowing the type is the top-level goal, the
>>> answer is simple: you can't.
>> 
>>    Knowing the type of a variable?
>> 
>>    It can be read from the declaration.
>> 
>>    For example,
>> 
>> double c;
>> 
>>    The type of »c« is double.
>
>
>That's a simple example. Try:
>
>    clock_t c;
>
>What's is the actual type of c? Or a little more challenging:

I have one (silly) answer.

$cat tmp.c
#include <stdio.h>
int main(void) {
	clock_t x;
	printf("%c\n", x);
}

$gcc -Wformat tmp.c
tmp.c: In function 'main':
tmp.c:4:18: warning: format '%c' expects argument of type 'int', but
argument 2 has type 'clock_t {aka long unsigned int}' [-Wformat=]
         printf("%c\n", x);
                 ~^
                 %ld


There, clock_t is long unsigned. I don't have any idea how to do this
at runtime, or with any other compiler.