https://github.com/mrquincle/ancient-c-compilers
Very old C compilers
https://github.com/mrquincle/ancient-c-compilers
Last synced: 3 months ago
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Very old C compilers
- Host: GitHub
- URL: https://github.com/mrquincle/ancient-c-compilers
- Owner: mrquincle
- Created: 2014-08-12T14:55:54.000Z (about 11 years ago)
- Default Branch: master
- Last Pushed: 2014-08-12T20:02:51.000Z (about 11 years ago)
- Last Synced: 2024-04-09T23:16:19.618Z (over 1 year ago)
- Language: C
- Size: 1.05 MB
- Stars: 21
- Watchers: 5
- Forks: 6
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Ancient C compilers
Stackoverflow, while a really great site, sometimes has a SPAM policy that is a bit too strict. Of course, it is logically they want to prevent people from advocating their own software. A question that would initiate a lot of answers regarding pointers to different ancient C compilers and would be a great resource for people online, [can not make it](https://stackoverflow.com/questions/25266909/where-is-the-source-code-for-the-earliest-c-compilers).
## Why bother about old code?
Links to old code give at times quite some authority to a question. See this reference to an analysis of source code of an early compiler, e.g.:
* [Why was the switch statement designed to need a break? where is referred to the Sun ANSI C compiler front end](https://stackoverflow.com/questions/252489/why-was-the-switch-statement-designed-to-need-a-break) by Peter van der Linden.
If you really want to know why `switch` statements have breaks or why other choices have been made, it might be worthwhile to look how they were used in the code. For example, I see a lot of fall-throughs in this code! Off-topic, but I think the real reason is different. A `switch` statement is quite a "flat" structure. A person who likes a `switch` statement does probably not like a piece of code like this (with implicit breaks):
switch(p) {
case 0:
if (error_cond1) {
// do something
} else {
if (error_cond2) {
// do something
} else {
// do something
}
}
case 1:
// do something
}
But probably more like this:
switch(p) {
case 0:
if (error_cond1) {
break;
}
if (error_cond2) {
break;
}
// do something
break;
case 1:
// do something
break;
}
Just my two cents, but I personally understand why people who love switches would love breaks as well, especially if the horizontal screen estate was much more limited in those days.
A quick `pcregrep -Mi 'case.*\n.*case' * | wc -l` in the `c` directory shows `166` fall-throughs by the way, and these are only subsequent `case` statements on subsequent lines. I would say, that's quite a lot on a total of `grep -ri case . | wc -l`: `459`.
# Source code
References to source code of early compilers:
* Ritchie [describes](http://www.cs.bell-labs.com/who/dmr/primevalC.html) a DECtape found by Paul Vixie and Keith Bostic. Which can be found on github elsewhere as well as [legacy-cc](https://github.com/mortdeus/legacy-cc). To honor Ritchie it is here added in his words as "primeval C".
* This code is by a combined effort from others combined to a running system at [google code](https://code.google.com/p/unix-jun72/), and put here in the folder [unix_v1].
* Sixth edition of Unix by Bell laboratories released in May 1975, which is designed to run on the PDP-11. The [files](http://minnie.tuhs.org/Archive/PDP-11/Distributions/research/Dennis_v6/) are from [Dennis Ritchie](https://en.wikipedia.org/wiki/Dennis_Ritchie). The compiler can be found in the [unix_v6] folder and then the `c/` directory.
# Todo
Cardeva made a lot of source available on the Unix Archive, e.g. see the [minnie.tush.org mirror](http://www.tuhs.org/Archive/PDP-11/Distributions/). Interesting code needs to be extracted from there.
# Documentation
* https://en.wikipedia.org/wiki/Portable_C_Compiler by Stephen C. Johnson of Bell labs in mid seventies
* https://en.wikipedia.org/wiki/Amsterdam_Compiler_Kit by Andrew Tanenbaum in early eighties (but not open-source of course, or we wouldn't have had gcc)
* https://en.wikipedia.org/wiki/GNU_Compiler_Collection by Richard Stallman in 1987