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Writing a C Compiler, in Zig (2025)

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Re: Writing a C Compiler, in Zig (2025)

#31

Post by groos »

I'm not sure why people seem to be under the impression that writing a compiler means that the language the compiler is implemented in should have "low level" features. A compiler is just a text -> text translation tool if you can leverage other tools such as an assembler and never needs to access machine level instructions. E.g., Pascal compilers have traditionally been written in Pascal, hardly a language which conjures up a "low level" image. Even when an assembler isn't available, all your implementation language needs to support, in terms of "low level" features, is writing of bytes to a file.

But manipulating instruction and file formats and such can be tedious if your language doesn't have the right capabilities but it's not impossible.

Re: Writing a C Compiler, in Zig (2025)

#32

Post by munificent »

groos wrote: post #31

I'm not sure why people seem to be under the impression that writing a compiler means that the language the compiler is implemented in should have "low level" features. A compiler is just a text -> text translation tool if you can leverage other tools such as an assembler and never needs to access machine level instructions. E.g., Pascal compilers have traditionally been written in Pascal, hardly a language which con…

> I'm not sure why people seem to be under the impression that writing a compiler means that the language the compiler is implemented in should have "low level" features.

Performance.

You definitely can write a compiler in a high-level language and given the choice I certainly prefer to on my hobby projects. Having a garbage collector makes so many compiler algorithms and data structures easier.

But I also accept that that choice means there's an upper limit to how fast my compiler will. If you're writing a compiler that will be used to (at least aspirationally) compile huge programs, then performance really matters. Users hate waiting on the compiler.

When you want to squeeze every ounce of speed you can get out of the hardware, a low-level language that gives you explicit control over things like memory layout matters a lot.

Re: Writing a C Compiler, in Zig (2025)

#33

Post by dwroberts »

mrkeen wrote: post #17
dwroberts wrote: post #5

Earlier quoted context omitted.

Feels like maybe something lost in translation with their explanation - they say they were fed up of data structures etc. but they returned to Rust? I’m assuming there’s something a bit more nuanced about what they got tired of with Zig

The author was fed up with not having data structures already provided, and needing to roll his own

Not really understanding what this would be though, zig has all the basic stuff you would expect in its stdlib (hashmap, queues, lists etc) just like Rust

Re: Writing a C Compiler, in Zig (2025)

#34

Post by LeFantome »

munificent wrote: post #32
groos wrote: post #31

I'm not sure why people seem to be under the impression that writing a compiler means that the language the compiler is implemented in should have "low level" features. A compiler is just a text -> text translation tool if you can leverage other tools such as an assembler and never needs to access machine level instructions. E.g., Pascal compilers have traditionally been written in Pascal, hardly a language which con…

> I'm not sure why people seem to be under the impression that writing a compiler means that the language the compiler is implemented in should have "low level" features. Performance. You definitely can write a compiler in a high-level language and given the choice I certainly prefer to on my hobby projects. Having a garbage collector makes so many compiler algorithms and data structures easier. But I also accept tha…

Does “low level” translate to performance? Is Rust a “low level” language?

Take C#. You can write a compiler in it that is very fast. It gives you explicit control over memory layout of data structures and of course total control over what you wrote to disk. It is certainly not “low level”.

Re: Writing a C Compiler, in Zig (2025)

#35

Post by NooneAtAll3 »

ecshafer wrote: post #8
dwroberts wrote: post #5

Earlier quoted context omitted.

Feels like maybe something lost in translation with their explanation - they say they were fed up of data structures etc. but they returned to Rust? I’m assuming there’s something a bit more nuanced about what they got tired of with Zig

I think Rust is "higher level" than C or Zig in the sense that there are most abstractions than C or Zig. Its not Javascript, but it is possible to program Rust without worrying too much about low level concerns.

> in the sense that there are most abstractions

is it a typo for more abstractions? or is there some different meaning?

Re: Writing a C Compiler, in Zig (2025)

#36

Post by ecshafer »

NooneAtAll3 wrote: post #35
ecshafer wrote: post #8

Earlier quoted context omitted.

I think Rust is "higher level" than C or Zig in the sense that there are most abstractions than C or Zig. Its not Javascript, but it is possible to program Rust without worrying too much about low level concerns.

> in the sense that there are most abstractions is it a typo for more abstractions? or is there some different meaning?

yes its a typo

Re: Writing a C Compiler, in Zig (2025)

#37

Post by dnautics »

flykespice wrote: post #22
Meneth wrote: post #21

Earlier quoted context omitted.

They kinda are: "This issue is to fully eliminate LLVM, Clang, and LLD libraries from the Zig project." https://github.com/ziglang/zig/issues/16270

I find that a very bold move, how will they reivent the wheel on the man-years of optimization work went into LLVM to their own compiler infrastructure?

They're just removing the obligate dependency. I'm pretty sure they will keep it around as a first-class supported backend target for compilation.

Re: Writing a C Compiler, in Zig (2025)

#38

Post by cxr »

groos wrote: post #31

I'm not sure why people seem to be under the impression that writing a compiler means that the language the compiler is implemented in should have "low level" features. A compiler is just a text -> text translation tool if you can leverage other tools such as an assembler and never needs to access machine level instructions. E.g., Pascal compilers have traditionally been written in Pascal, hardly a language which con…

This comment started out strong, but then:

> Pascal compilers have traditionally been written in Pascal, hardly a language which conjures up a "low level" image.

It may be the case that it doesn't conjure up such an image, but Pascal is approximately on the same rung as Zig or D—lower level than Go, higher level than assembly. If folks have a different impression, the problem is just that: their impression.

Re: Writing a C Compiler, in Zig (2025)

#39

Post by bsder »

munificent wrote: post #32
groos wrote: post #31

I'm not sure why people seem to be under the impression that writing a compiler means that the language the compiler is implemented in should have "low level" features. A compiler is just a text -> text translation tool if you can leverage other tools such as an assembler and never needs to access machine level instructions. E.g., Pascal compilers have traditionally been written in Pascal, hardly a language which con…

> I'm not sure why people seem to be under the impression that writing a compiler means that the language the compiler is implemented in should have "low level" features. Performance. You definitely can write a compiler in a high-level language and given the choice I certainly prefer to on my hobby projects. Having a garbage collector makes so many compiler algorithms and data structures easier. But I also accept tha…

> But I also accept that that choice means there's an upper limit to how fast my compiler will.

Don't buy it.

A decent OCaml version of a C or Zig compiler would almost certainly not be 10x slower. And it would be significantly easier to parallelize without introducing bugs so it might even be quite a bit faster on big codebases.

Actually designing your programming language to be processed quickly (can definitively figure things out with local parsing, minimizing the number of files that need to be touched, etc.) is WAY more important than the low-level implementation for overall compilation speed.

And I suspect that the author would have gotten a lot further had he been using a GC language and not had to deal with all the low-level issues and debugging.

I like Zig, and I use it a lot. But it is NOT my general purpose language. I'm definitely going to reach for Python first unless I absolutely know that I'm going to be doing systems programming. Python (or anything garbage collected with solid libraries) simply is way more productive on short time scales for small codebases.

Re: Writing a C Compiler, in Zig (2025)

#40

Post by bsder »

flykespice wrote: post #22
Meneth wrote: post #21

Earlier quoted context omitted.

They kinda are: "This issue is to fully eliminate LLVM, Clang, and LLD libraries from the Zig project." https://github.com/ziglang/zig/issues/16270

I find that a very bold move, how will they reivent the wheel on the man-years of optimization work went into LLVM to their own compiler infrastructure?

Proebsting's Law: Compiler Advances Double Computing Power Every 18 Years

You need to implement very few optimizations to get the vast majority of compiler improvements.

Many of the papers about this suggest that we would be better off focusing on making quality of life improvements for the programmer (like better debugger integration) rather than abstruse and esoteric compiler optimizations that make understanding the generated code increasingly difficult.

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