AW: AW: Feature request for "friendship" of pointers in "C"

[aotto]

Ok, it seems that I'was not convinced about the "safty" of "&aOut->out" 
but it seems
that (at least gcc) add the aOut into the first item of "method_base".
-> This is infact the "frienddef" I required by "default" :-)

so - it seems it was my fould. and the tool https://godbolt.org/z/e_z8_y 
include compile test
helped.

On 03.02.20 11:02, J Decker wrote:
>
>
> On Mon, Feb 3, 2020 at 1:38 AM aotto <aotto1968@t-online.de 
> <mailto:aotto1968@t-online.de>> wrote:
>
>     Hi, as i mentioned earlier… the "not having" create a couple of
>     problems:
>
>     1. the "void-pointer-inflation"
>     Â Â  you can rewrite "method_base(struct base* hdl, ...)" win
>     Â Â  "method_base(void* hdl, ...)" this seems to solve the problem
>     Â Â  BUT you definitely loos the type-check because other pointer as
>     "A" and "B"
>     Â Â  also allowed.
>
>
>     2. the "cast inflation"
>     Â Â  you can add the "CPP" wrapper to "method_base" this will act
>     like "void*"
>     Â Â  but you loose the "type-check also"
>
>
>     3. even if you use "&aObj->obj" this create EXTRA CODE which add
>     only CRASH-scenarios
>        and add EXTRA overhead…
>
>     3. there is only ONE clear solution which NOT loose the
>     "type-checking" and DON'T add
>     Â Â  extra code and this solution is the "frienddef"
>
>
> None of these are an issue, unless you're actually trying to go the 
> other direction (getting an A* for B* from a base*), which none of 
> your examples are exemplifiying....
> 1) nothing prevents you from passing the address of the base structure
> 2) I think you mean #define wrapper; which can still have your 
> in-library type check for 'is a valid X'
> 3) does not create extra code, since your base pointer is the base of 
> your structure, it'll still be NULL, unlike other places... you've 
> already constrained it that it's the first member.
> 3(2)) since the rest of the points aren't themselves valid it doesn't 
> appear there really needs to be an additional solution...
>
>
>     mfg AO
>
>     On 03.02.20 10:20, J Decker wrote:
>>
>>
>>     On Mon, Feb 3, 2020 at 1:10 AM aotto <aotto1968@t-online.de
>>     <mailto:aotto1968@t-online.de>> wrote:
>>
>>         On 03.02.20 10:07, J Decker wrote:
>>         > On Mon, Feb 3, 2020 at 12:23 AM aotto
>>         <aotto1968@t-online.de <mailto:aotto1968@t-online.de>> wrote:
>>         >
>>         >> Hi,
>>         >>
>>         >> there is an easy test, if Stefan is right and I'm wrong.
>>         >>
>>         >> 1. cast an INVALID Pointer to "aObj"
>>         >>
>>         > how would friend prevent an invalid pointer pass?
>>         → I have a pointer-type-and-valid test in my software, this mean
>>         Â Â  I know if a pointer is "valid" or not... but this works
>>         only if
>>         Â Â  I get the pointer into my "base_method".
>>
>>
>>     C doesn't have any such thing, no do any other developer, so how
>>     would it help them? (you fell off the list)
>