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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: do { quit; } else { }
Date: Tue, 08 Apr 2025 14:18:30 -0700
Organization: A noiseless patient Spider
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bart <bc@freeuk.com> writes:

> On 08/04/2025 18:32, Tim Rentsch wrote:
>
>> bart <bc@freeuk.com> writes:
>>
>>> On 08/04/2025 15:50, David Brown wrote:
>>>
>>>> On 08/04/2025 13:35, bart wrote:
>>>>
>>>>> But this need not be the case.  For example this is module A:
>>>>>
>>>>> --------------------------
>>>>>   #include <stdio.h>
>>>>>
>>>>>   typedef struct point {float a; float b;} Point;
>>>>>
>>>>>   float dist(Point);
>>>>>
>>>>>   int main(void) {
>>>>>   Point p = {3, 4};
>>>>>   printf("%f\n", dist(p));
>>>>>   }
>>>>> --------------------------
>>>>>
>>>>> And this is module B that defines 'dist':
>>>>>
>>>>>
>>>>> --------------------------
>>>>>   #include <math.h>
>>>>>
>>>>>   typedef float length;
>>>>>   typedef struct _tag {length x, y;} vector;
>>>>>
>>>>>   length dist(vector p) {return sqrt(p.x*p.x + p.y*p.y);}
>>>>> --------------------------
>>>>>
>>>>> The types involved are somewhat different, but are compatible
>>>>> enough for it to work.
>>>>
>>>> The two types are entirely compatible.
>>>
>>> Are they?
>>
>> No, they are not.  The type names 'Point' and 'vector' name two
>> distinct types, and those types are not compatible, because
>> the two struct tags are different.
>>
>> Because the two types are not compatible, even just calling the
>> function dist() is undefined behavior.
>
> I get an incompatible error (from the example you snipped) even when I
> remove both struct tags.
>
> I can't use the same struct tag in the same scope as one will clash
> with the other.  But if I have the second in an inner scope, then I
> again get the error.

If you want to make a point or ask a question about C code,
SHOW THE CODE.  And show all of it.  Don't make people guess
by showing only some of the code or by giving just a description.