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From: bart <bc@freeuk.com>
Newsgroups: comp.lang.c
Subject: Re: do { quit; } else { }
Date: Thu, 10 Apr 2025 20:11:01 +0100
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On 10/04/2025 17:51, Kaz Kylheku wrote:
> On 2025-04-10, bart <bc@freeuk.com> wrote:

>> In my C compiler, each type has a unique index which is what is compared
>> to see if two types are the same type. It has nothing to do with tags.
> 
> How can it not?
> 
>    struct tag;
>    struct tag { ... };
> 
> these have to refer to the same type; how do you do that without tags?

The type can be denoted in the source code using 'struct tag'. Looking 
'tag' up in the ST, checking only names belonging to the special tag 
namespace, will yield an entry that has its type index, whatever that 
happens to be.

But the tag is not what is used when comparing two types. It is just an 
anachronistic concept that C still needs.

(In C++ I understand that special tag namespaces don't exist, they are 
just part of the normal namespace.

And in my languages they have never been a concept, yet I can still 
compare one struct type with another.)