Re: [Freedos-kernel] Compilers (the eternal topic :)

[Luchezar G. <lu...@co...>]

Hallo Bart,

> Question is how much of a difference can you tolerate? From you I get 
> the impression that a 100K uncompressed kernel that compresses to 39999 
> bytes would be preferable to a 64K one that compresses to 40000 bytes.

;-) I could never use an uncompressed kernel that is below 64 KB. 
OpenWatcom makes the FAT32/80386 unstable kernel 66330 bytes long. The 
maximum size that UPX accepts is 65350 bytes. The difference is almost a 
kilobyte. How could we reduce the kernel further without crippling it? 
It's difficult!

> I've seen compressed differences between Turbo C++ 1.01 and OW going 
> down over the years. As for Borland, is it worth spending $59+postage 
> for an unsupported product on an obscure Ebay site when so many free 
> compilers are available?

It's not worth a penny because it can be freely downloaded from Vietnam (I 
posted the URL here ;-)

> How about Digital Mars for instance?

A very good compiler in my opinion, backed by Walter Bright's C++ great 
compiler "know-how", but Tom once wrote that he gave up porting the kernel 
to it as he didn't see advantages.

> I experimented a bit -- as it turns out once the uncompressed size goes 
> to <64K you can stick on a SYS header to kernel.sys, UPX the already 
> exeflatted SYS file and use that. For some reason in this case UPX is 
> better than APACK by the way. Well I got it down to ~41300 bytes vs. 
> your 40957. Now you're just lucky that 40957 is just below the 80 sector 
> boundary but the difference is gone at 40961 bytes.

Does that < 64K kernel support FAT32? Hardly. The 40K one at my site does. 
So that's an incorrect comparison. Besides, aPack doesn't compress .SYS 
files at all. An incorrect comparison again.

> Did I say it was bad? I just claim it's not the best tool for our job 
> and has several other disadvantages.

You're right, but I have to put up with its disadvantages for one big 
advantage - KING SIZE! ;-)

> Do Datalight really use it because the entropy is lower so the 
> compressed size goes down?

Their DOS is not compressed at all, although I offered them some stubs to 
compress a < 64K kernel.

> Of course they lost the "race" (MSVC, Intel, GCC) when Sybase took over 
> and eventually stopped development. And from what I gather 11.x however 
> introduced various obscure linker bugs, and loop optimization bugs (most 
> are fixed in OW now). And OW still has years to catch up in terms of 
> C++ standards (slowly getting there).

The information about loop optimisation bugs is very important. So, not 
all of them are fixed yet? For example a colleague of mine discovered such 
a bug which I reported to them. It's present in all Watcoms since 11.0 but 
wasn't there in 10.6!

Unfortunately, there are no bug-free compilers :-(

Regards,
Lucho