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From: Richard Damon <richard@damon-family.org>
Newsgroups: comp.lang.c
Subject: Re: relearning C: why does an in-place change to a char* segfault?
Date: Sun, 4 Aug 2024 07:22:57 -0400
Organization: i2pn2 (i2pn.org)
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On 8/3/24 10:58 PM, Keith Thompson wrote:
> Lawrence D'Oliveiro <ldo@nz.invalid> writes:
>> On Sat, 03 Aug 2024 17:07:37 -0700, Keith Thompson wrote:
>>
>>> ... general compression isn't something I've seen ...
>>
>> I recall Apple had a patent on some aspects of the “PEF” executable format
>> that they created for their PowerPC machines running old MacOS. This had
>> to do with some clever instruction encodings for loading stuff into
>> memory.
> 
> Is that relevant to what I asked about?
> 
> What I had in mind is something that, given this:
> 
>      static int buf = { 1, 1, 1, ..., 1 }; // say, 1000 elements
> 
> would store something less than 1000*sizeof(int) bytes in the executable
> file.  I wouldn't be hard to do, but I'm not convinced it would be
> worthwhile.
> 

I vaguely seem to remember an embedded format that did something like 
this. The .init segement that was "copied" to the .data segement has a 
simple run-length encoding option. For non-repetitive data, it just 
encoded 1 copy of length n. But it could also encode repeats like your 
example. When EPROM was a scarce commodity squeezing out a bit of size 
for the .init segment was useful.

My guess that since it didn't persist, it didn't actually help that much.