Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: James Kuyper <jameskuyper@alumni.caltech.edu>
Newsgroups: comp.lang.c
Subject: Re: do { quit; } else { }
Date: Tue, 13 May 2025 22:23:48 -0400
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On 5/13/25 20:51, Keith Thompson wrote:
> James Kuyper <jameskuyper@alumni.caltech.edu> writes:
>> On 5/13/25 05:40, David Brown wrote:
....
>>> Yes. Basically, most C programmers are not particularly aware of the
>>> technical definitions of some of the terms in C standards where they
>>> differ from common usage. The word "compatible" in English means that
>>> the things in question can work together or fit together.
>>
>> That's pretty much what it means in C. Two C types are compatible in C
>> if the C standard *guarantees* that they can work together - that you
>> can use the types interchangeably. The tricky part is the definition of
>> which pairs of types the C standard makes those guarantees for.
>> The key point is that the undefined behavior of code which treats
>> incompatible types as if they were compatible could also be that they
>> work together, too, depending upon the implementation.
> 
> I suggest that the phrase "work together" is too vague.

I was trying to match the wording of the text I was responding to. What
I meant can be made far more precise: the C standard guarantees that two
compatible types will work together, in the sense that every case where
the C standard mandates that two types must be compatible in order for
something to work, it will work for them.