Re: relearning C: why does an in-place change to a char* segfault?

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.