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C compiler #1443
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Hello @stevexyz, Thanks for your interest in ELKS. A few years back, the project switched from using bcc to ia16-elf-gcc to build the kernel and all the applications. One of the big reasons was the lack of support for 8086 segmented architecture linker and compiler options that are not present in bcc (or tcc). Unfortunately, gcc is way too large to be able to be included in ELKS runtime, so there isn't a way for ELKS to be self-compiled, but this has been viewed as a reasonable tradeoff, all things considered. I'm a fan of tcc, but the question is, given the limitations of segmented-mode 8086, what purpose would it serve, doing the work to get a self-hosted compiler running, when none available contain the features required to build the current kernel and all of the applications? Thank you! |
To me a C compiler is the base of a complete Linux (Unix) system... |
Hi @stevexyz -
Here's the the thing: ELKS is not a complete Linux or Unix system. Like the name says, it's intended for embedded systems. Embedded systems have limited resources and are rarely if ever selfcompiling. Of course our vintage PCs aren't embedded systems, but they have very limited resources. And - as @ghaerr also alluded to - it just doesn't make sense to have that ambition. Possibly fun, but not useful. Think about it - what we have today is a cross development environment with I have Venix running on one of my machines, a 286/12. It's a complete Unix system. It can compile itself if I had full sources, and I've done a lot of development on it. In the mid 80s and recently. It has
Yes, the compilers you're referring to RUN on the segmented architecture, but they support only parts of it – the small, maybe medium memory model, that's all. They have very limited options and support-tools (like
ELKS has come a long way, the last few years in particular. Your contributions would be very welcome. Even a native C-compiler. It's your time and your choice - and you'll get plenty support from the group regardless of whether the target tool/application is for the few or the many. --M |
Not for self-compiling but to make small debug program, it is nice to have a small compiler on ELKS. I now uses the basic to peek memory or read ports on the real PC from the background but sometimes wants to do a little more complicated. |
As already mentioned by @tyama501 it was not to be used to self compiling, even if it would have been a nice thing. And especially for starting, if there is something that is ready to be used, doesn't really matter if it is supporting just a limited memory model, but at least you can compile and run some programs on the system without always access another computer. For now I've other (unfortunately too many) projects going on and I'll stay on the window looking the ways ELKS will grow up, but in the future if it will still be not developed maybe I'll give it a try! In the meantime keep up the good work and happy hacking! |
I thought more deeply about exactly what is entailed when someone says "I'd like a C compiler" to run native on ELKS. As @tyama501 and @stevexyz mentioned, it would be nice to be able to at least just compile some programs from within ELKS. In order to do that, we'd need the following:
After all this, there are all the issues that @Mellvik brings up, which include problems associated with having no All in all - I have agree with @Mellvik that such a project is not really what people think of "having a C compiler" for ELKS. On another note, I was thinking about some C interpreters that might be able to provide fast execution of simple C programs, such as the C in 4 functions compiler. It is very cool with a small code size, and allows for calling out of various functions like Thank you! |
Hello @stevexyz, @ghaerr, @tyama501, I suspect that the Amsterdam Compiler Kit might be a good candidate for an ELKS-hosted C compiler, though I have not really got around to working on such a thing, and it probably needs a fair amount of effort. I believe ACK used to be the standard toolchain for Minix — including Minix/8086 — and besides, it is written to be able to run on small systems. Thank you! |
Seems to me that https://github.com/alexfru/SmallerC would be a very good start: seems easy enough and producing already 16 bit x86 code in various models, and with self compilation the ported compiler if it will produce the binary elk file. Maybe the author itself would adapt it if requested and specification of the binary file are given: if it is considered good we can try to ask. PS: @ghaerr I had a look at c in 4 functions, and while being an amazing exercise of minimization, seems really not easy to port to minimal memory systems for the way it has been designed |
just as comment, I tried to play with old "ACK for Minix" from https://web.archive.org/web/20070910201015/http://www.laurasia.com.au/ack/index.html#download on Minix i86 (not i386) qemu VM. Well, it ran out of memory :) trying to compile itself under existing 'cc' compiler there. |
Also, Portable C Compiler website seems to be down (and web archive does not have latest copy) so here I found slightly updated (2021) copy of code https://github.com/matijaskala/pcc There seems to be some code related by i86 generation by Alan Cox. Also, someone (Eric J. Korpela) looked at lcc-8086 but not get very far |
Hello @Randrianasulu and @tkchia, Thank you @Randrianasulu for the links to PCC, I'll take a look at it. Same for LCC-8086, that work looks extremely old but could be worthwhile. Of course, it would probably be a good idea to consider only using ANSI-capable (vs K&R) compilers, given where most C code is at today.
It's probably not needed that the compiler be able to compile itself under ELKS (or MINIX), so that's OK. I am not familiar to what degree ACK has been updated to any ANSI standards, and/or long/long log/float support etc. In the case of running on ELKS, we now have the issue that some portions of the C library may be using some @tkchia, you had mentioned you're possibly somewhat familiar with ACK, would that be a version similar to that used for MINIX as described above, or has there been more work done updating it, to your knowledge? Thank you! |
@ghaerr I found little something supposed to help with backtranslating ANSI C to older dialect: Also, may be Xenix (286) a.out variant can be used to get some idea how multiple segments were supported. https://ibcs-us.sourceforge.io/ |
Hello @ghaerr,
I have not yet done a comparison of the "laurasia" copy of ACK, and David Given's current ACK tree — I hope to do that soon. At the moment I am more familiar with Mr. Given's source tree (since I have been working on it a bit). Some impressions:
Thank you! |
slightly newer ackpack for minix (1.1.2) weirdly it comes as tar.tar. I only get file by downloading it via browser, not via wget. Same source should still be in Minix3 git, but a bit obscured because it was deleted years ago ... info from |
so, there was another compiler (c86 ?) but license prohibit commercial use. https://github.com/plusk01/8086-toolchain/tree/master/compiler |
https://web.archive.org/web/20150908032106/http://homepage.ntlworld.com/itimpi/compsrc.htm - so it was named c68, too ... |
ah, it was not complete compiler, just c to asm (nasm in this version) compiler. It needed cc (main driver), ld86 (linker), c preprocessor (it seems for Psion 3 they tried Decus cpp, available in X11R3 distribution - not tried to build it yet). So, some sources are newer in C68 (for QDOS - mk68k/ Sinchlair QL system) but part of older EPOC sources still live at older site: http://web.archive.org/web/20010414060410/http://www.itimpi.freeserve.co.uk/cpocdown.htm#SOURCE |
Seems has already a lot of options, among them the ones for 8086 specific:
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so, I have something horribly broken, but it makes .o files! https://github.com/Randrianasulu/c86 make on linux/termux should give you some binaries. |
@Randrianasulu : it is almost certainly still not GPL-compatible though. |
seems to be very detailed document about c68 by author (I tried to send email to him, but no idea if old email address still works) |
https://qlforum.co.uk/viewtopic.php?t=2112 - may be he has new email, forwarded to it too |
just at the beginning of the C68 QL manual it says that it is Public Domain (even with capitals): INTRODUCTION |
Hello @stevexyz, I mentioned this because @Randrianasulu stated that the source files themselves seem to prohibit commercial use. And I see that Thank you! |
little aside (feel free to hide) but MAME got Psion 3 emulation inmore working state lately https://forums.bannister.org/ubbthreads.php?ubb=showflat&Number=121869&page=3 |
also faucc (286 & 386 codegen only?) https://gitlab.cs.fau.de/faumachine/faucc/-/commits/master EDIT: sadly it does not compile faumachine's new bios :( also, no FP. so, not very useful? |
Just a sidenote, but I think NASM does support ELKS a.out format. LCC port might use NASM too. Anyways, last time I looked into ELKS binary format it had some limits on DATA and CODE segment sizes similar to Minix 1. Is that still the same? What are the limits? Is it now possible to make something like large memory model executables in MS-DOS with GCC-iA16? |
I'm not sure about whether NASM supports a 16-bit MINIX a.out format or not. Does NASM support ELF output? If so, the binary could likely be converted to ELKS a.out format using our own The ELKS toolchain and kernel currently offer the ability to create and run small (64K code, 64K data) and medium (128K code, 64k data) model programs. Access to a larger data segment is possible through C |
I took a peek at NASM. It doesn't support Minix/ELKS directly. It supports as86 obj files though. They could be then linked with ld86 into elks binary, I think. My memory is a bit murky on this. Thanx for the info on memory model support ghaerr. Much appreciated. |
I'm using dev86 cpp. It seems be working ok. I added to the 8086-toolchain repo: |
Nice, good news about using dev86 cpp! I'm running a host version of c86 for now, and giving it preprocessed input using |
More information on CC386 v4.2.0: https://ladsoft.tripod.com/cc386_compiler.html Looks like it was maintained for quite a while into 2017 and then replaced by Orange C. There are apparently Win32 and DOS 16-bit versions. |
No idea. But now I'm running it with "-m16". |
What about dev86 linker? Is that of any use? I think I successfully cross-compiled it (or at least one of its earlier versions) using dev86/bcc a decade or so ago and it ran on ELKS without any problems. I think assembler cross-compiled easily, too. This, of course, doesn't work with ELF. Only with a classic Minix format (I mean older than V3). |
Hi Bocke. Indeed, I thought about ld86, but the problem is that I don't think it can link any of the nasm output formats. If ld86 is useful, then I think it would be relatively easy to port. |
Just double checked - nasm has indeed as86 output. |
I have opened a new issue #2112 for all comments regarding getting @rafael2k's 8086-toolchain (C86, NASM, CPP, LD) running on ELKS. Please post there for details on that specific port, as this issue is getting quite long and should pertain to discussions about general C compilers and their feasibility for running on ELKS. |
Fuzix C compiler does not generate code for 8086 (but it does for 8080 and 8085), and seems also an interesting option if it gets a 8086 backend. |
It's got most of an 8086 backend written but not tested out. Need to finish the assembler first |
That is really good news @EtchedPixels ! Yay! |
For the reference, another interesting compiler which can generate 8086: |
Native ELKS C tool chain starting to work! |
I would like to add a C interpreter: https://gitlab.com/zsaleeba/picoc as a suggestion for an interpreter/compiler to be ported. |
Just for the heck of it I took a few minutes to look at the source code of PicoC. I guess I should not be surprised, as these days any programs with nano- or pico- in the name seem to be super large. And PicoC requires lots and lots of RAM, even though it says it's great for embedded systems (!). Here's one of the first lines in pico.c:
Yep - you got it, 128K stack. LOL!!!
It would be nice to have a good library of C source code for compiler testing - so I took a quick look at a test source file:
Here you can see a printf function call directly in the declarations-only area of supposed "C" - completely illegal for any C compiler. Looking further, most all the tests are coded like this, in script-like fashion (after all, PicoC is a scripting language). So it seems this is another "modern" program dependent on a large address space - exactly what we don't have on ELKS. |
Take a look at the Fuzix ones if you need one bunch - there's a minimal test set in test/ and a fancier test set in the wtest subdir that Warren contributed. They need very little on the CPU emulator hooks to run quite good tests. SDCC has a bunch too. It may depend how optimizing your compiler is too - some of the tests will optimize out with a good compiler |
I was browsing something related to classic Minix (before 3.x) and found versions of C68/C86 ported to Minix here: http://ftp.funet.fi/pub/minix/lang/c68/. These are older versions from 1991/1992. So more of a curiosity. Posting for reference and completeness, |
@EtchedPixels, could you please confirm the path on Fuzix repo tree where the tests are? |
Nice find @bocke! We forked at v5.1, not sure whether version number was incremented by the BYU folks or whether that's what they started with - but having v1, v3 and v4 of C86 is very interesting. I'll have a look. I'm very impressed with the C86 compiler, as far as how it is internally written and was designed. I had never heard of it, but can see that tons of work went into it in the day. These older versions may shed more light on its history, of which I remain very interested. |
Thanks - I'll take a look at the test suites. C86 isn't an optimizing compiler in any modern sense of the word - no data flow analysis and no dead code elimination, for instance. Constant folding and other peephole-style optimizations are done post parse-tree processing by apparently converting the parse tree to a code generation tree, optimized, and then traversed again for actual (assembly language) code generation. The compiler has it's roots in the 68000 (and possibly 6809?) CPU, but long ago, some folks went to the trouble of adding support for PPC, ARM, the TMS320C30 signal processor, 8086 and 8036, all output as ASM source, some for multiple assembler input format languages. For our needs, I kind of like the ASM rather than object output, as it allows for changing up the toolchain and possibly introducing other linkers, without having to hack the compiler at all. (Well, except for those nasty .comm/common variables and other assorted stuff requiring linker magic!). |
@rafael2k, they're over in the CompilerKit repo: https://github.com/EtchedPixels/Fuzix-Compiler-Kit/tree/main/test |
I published ELKS devkit v0.1. Still very very early days, and no libc yet: Included software: ar86 as86 c86 cpp86 disasm86 ld86 make nasm ndisasm objdump86. |
Maybe this is obvious, but this is the toolchain compiled to be executed under ELKS (not the host Linux, right)? |
On ELKS, yes! |
ELKS DevDisk v0.2 available:
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Currently we have a working improved C compiler and instructions on how to build it in: #2159 |
Maybe I'm wrong (I just tried to install elks on an original PC IBM XT), but seems to me that no C compiler is included inside elks (I've found the basic language interpreter though), while I think that's one of the basic thing of every Linux system.
If that's the case, I understand that a mammoth GCC might not really fit the project, but maybe the small and powerful tcc might be an option!
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