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Writing a C compiler in 500 lines of Python (2023)

vgel.me

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Re: Writing a C compiler in 500 lines of Python (2023)

#11

Post by amszmidt »

emilbratt wrote: post #9
tvickery wrote: post #3

[flagged]

That is not a compiler. That is called a wrapper script. But funny none the less.

The original cc was just a wrapper like this Python example around a bunch of external programs, calling c00, c01, until something could be fed to as and then linked using ld.

GCC does basically the same thing even today,

Re: Writing a C compiler in 500 lines of Python (2023)

#12

Post by bluGill »

weregiraffe wrote: post #2

Now write a Python compiler in 500 lines of C.

I could probably do it - but you wouldn't like it. My dictionaries would be a linked-list, looking for a key becomes a linear search... (if you gave me C++ I'd use std::map) I'm assuming you will allow me to use the C standard library, if I have to implement strlen or malloc in that 500 lines of C I'm not sure I can pull that off. 500 lines is aggressive, but IOCCC gives me plenty of tricks to get the line count down and the language isn't that big. I'm also going to assume 100% valid python code is fed in, if there is a bug or error of any sort that is undefined behavior.

Note that most of what makes python great isn't the language, it is the library. I believe that large parts of the python library are also written in C (for speed), and thus you won't be able to use my 500 line python compiler for anything useful because you won't have any useful libraries.

Re: Writing a C compiler in 500 lines of Python (2023)

#13

Post by 01HNNWZ0MV43FF »

amszmidt wrote: post #11
emilbratt wrote: post #9

Earlier quoted context omitted.

That is not a compiler. That is called a wrapper script. But funny none the less.

The original cc was just a wrapper like this Python example around a bunch of external programs, calling c00, c01, until something could be fed to as and then linked using ld. GCC does basically the same thing even today,

yeah but c00 and c01 actually do stuff

Re: Writing a C compiler in 500 lines of Python (2023)

#16

Post by TZubiri »

01HNNWZ0MV43FF wrote: post #13
amszmidt wrote: post #11

Earlier quoted context omitted.

The original cc was just a wrapper like this Python example around a bunch of external programs, calling c00, c01, until something could be fed to as and then linked using ld. GCC does basically the same thing even today,

yeah but c00 and c01 actually do stuff

So does gcc

Re: Writing a C compiler in 500 lines of Python (2023)

#17

Post by MarsIronPI »

I find it surprising that a single-pass compiler is easier to implement than a traditional lexer->parser->AST->emitter. (I'm not a compiler expert, though.) I'd have expected that generating an AST would be at least as simple, if not simpler. Plus by generating an AST, doing some simple optimization is a lot easier: one can pattern-match parts of the AST and replace them with more efficient equivalents. Maybe I'm overthinking this, though. I tend to like extensible program designs, even when they don't necessarily make sense for the scale of the program…

Still a really cool article and an impressive project, though. I especially like the StringPool technique; I'll have to keep it in mind if I ever write a compiler!

Re: Writing a C compiler in 500 lines of Python (2023)

#19

Post by arjvik »

MarsIronPI wrote: post #17

I find it surprising that a single-pass compiler is easier to implement than a traditional lexer->parser->AST->emitter. (I'm not a compiler expert, though.) I'd have expected that generating an AST would be at least as simple, if not simpler. Plus by generating an AST, doing some simple optimization is a lot easier: one can pattern-match parts of the AST and replace them with more efficient equivalents. Maybe I'm ove…

Not sure if fewer LoC necessarily implies easier!

Re: Writing a C compiler in 500 lines of Python (2023)

#20

Post by lukan »

Liftyee wrote: post #6

This article breaks it down well enough to make me feel like I could write my own C compiler targeting AVR. (I probably could... but it would not be easy.) Never actually looked into how compilers work before, it's surprisingly similar/related to linguistics.

"compilers work before, it's surprisingly similar/related to linguistics."

Since compilers transform languages with a clearly defined grammar ... the connection to linguistics is maybe not so surprising after all.

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