BCPL was too large and sophisticated to be implementable on early Unix systems. The first C compiler emitted machine code directly from the parser (as does SectorC), because there wasn’t enough memory to build a parse tree. According to Dennis Richie, BCPL couldn’t be implemented that way, because of advanced features such as: you can call a procedure before it is declared, and block expressions (these were called valof expressions in BCPL).
Richie describes B (the predecessor of C) as “BCPL squeezed into 8K bytes and filtered through [Ken] Thompson’s brain”. B also had only 1 type, a 16 bit word, and SectorC seems to be the same, although it calls this type “int”. So SectorC is much closer to B than it is to BCPL.
In how many of the systems programming languages lot can something like this be possible? (single person hobby, of a compiler that covers a very useful set of the features of the language in 512 bytes)
The Turbo Pascal environment for DOS, with a compiler, pseudographical IDE, debugger, a set of libraries all fit in 300 KB, if I remember correctly. I suspect its subset could be implemented succinctly as well.
It just becomes a game of “how many features I can leave out while it’s still resembling something serious”, a code golf to compress compiler concepts and language features.
Is it a coincidence that “Barely C Programming Language” abbreviates to BCPL?
I’m not really clear on what happened in between the “lex it like Forth” step and the “Profit!” Step, but it’s cool.
BCPL was too large and sophisticated to be implementable on early Unix systems. The first C compiler emitted machine code directly from the parser (as does SectorC), because there wasn’t enough memory to build a parse tree. According to Dennis Richie, BCPL couldn’t be implemented that way, because of advanced features such as: you can call a procedure before it is declared, and block expressions (these were called
valofexpressions in BCPL).Richie describes B (the predecessor of C) as “BCPL squeezed into 8K bytes and filtered through [Ken] Thompson’s brain”. B also had only 1 type, a 16 bit word, and SectorC seems to be the same, although it calls this type “int”. So SectorC is much closer to B than it is to BCPL.
See: https://www.lysator.liu.se/c/chistory.ps
This is absolutely horrifying, and I love it!
All the best,
This is an amazing feat. But shouldn’t the post title be “SectorC: A C Compiler in 512 bytes”?
In how many of the systems programming languages lot can something like this be possible? (single person hobby, of a compiler that covers a very useful set of the features of the language in 512 bytes)
The Turbo Pascal environment for DOS, with a compiler, pseudographical IDE, debugger, a set of libraries all fit in 300 KB, if I remember correctly. I suspect its subset could be implemented succinctly as well.
It just becomes a game of “how many features I can leave out while it’s still resembling something serious”, a code golf to compress compiler concepts and language features.