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From: Tim Rentsch <tr.17687@z991.linuxsc.com>
Newsgroups: comp.lang.c
Subject: Re: transpiling to low level C
Date: Sat, 28 Dec 2024 09:24:16 -0800
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BGB <cr88192@gmail.com> writes:

> On 12/23/2024 3:18 PM, Tim Rentsch wrote:
>
>> Michael S <already5chosen@yahoo.com> writes:
>>
>>> On Mon, 23 Dec 2024 09:46:46 +0100
>>> David Brown <david.brown@hesbynett.no> wrote:
>>>
>>>> And Tim did not rule out using the standard library,
>>>
>>> Are you sure?
>>
>> I explicitly called out setjmp and longjmp as being excluded.
>> Based on that, it's reasonable to infer the rest of the
>> standard library is allowed.
>>
>> Furthermore I don't think it matters.  Except for a very small
>> set of functions -- eg, fopen, fgetc, fputc, malloc, free --
>> everything else in the standard library either isn't important
>> for Turing Completeness or can be synthesized from the base
>> set.  The functionality of fprintf(), for example, can be
>> implemented on top of fputc and non-library language features.
>
> If I were to choose a set of primitive functions, probably:
>   malloc/free and/or realloc
>     could define, say:
>       malloc(sz) => realloc(NULL, sz)
>       free(ptr) => realloc(ptr, 0)
>     Maybe _msize and _mtag/..., but this is non-standard.
>       With _msize, can implement realloc on top of malloc/free.
>
> For basic IO:
>   fopen, fclose, fseek, fread, fwrite
>
> printf could be implemented on top of vsnprintf and fputs
>   fputs can be implemented on top of fwrite (via strlen).
>   With a temporary buffer buffer being used for the printed string.

Most of these aren't needed.  I think everything can be
done using only fopen, fclose, fgetc, fputc, and feof.