5 ms·

c4wa – C compiler for Web Assembly

91 points by 90s_dev 1y ago

comex 1y ago
In the comparison with Emscripten using wasm-decompile [1], the author appears to have forgotten to turn on optimization. Yes, if you run emcc with no -O option then you will get extremely bad generated code quality, similar to most C compilers. Add -O and you get nice and tight code similar to what c4wa outputs. [1] https://github.com/kign/c4wa/blob/master/etc/doc/comparison.md https://github.com/kign/c4wa/blob/master/etc/doc/comparison....
- soegaard 1y ago
  I think, the author's goal was to produce wasm-code that had the same structure as the original C. Thus it makes sense to turn off the advanced optimizations.
lioeters 1y ago
> c4wa needs Java 11 or above It sounded good until this part. Would have been nice if it were written in the subset of C that it supports, so it could compile the compiler to Wasm.
apitman 1y ago
This is actually pretty compelling to me. I think the more support for freestanding wasm modules the better. I'm working on a custom wasm app runtime and I don't want to have to implement the entire API surface of Emscripten or WASI. The new component model is even more complex. I wish there was more tooling available for using C/Rust stdlib functions for things like reading files or opening a socket, but being able to define your own API to handle the actually operations in the host/module interface.
pyrolistical 1y ago
Zig can also compile to free standing wasm
- jeden 1y ago
  any example? I search wasm without js.
  - whitehexagon 1y ago
    I noticed this question yesterday, which includes the changed build options for freestanding. https://ziggit.dev/t/wasm-index-out-of-bounds-only-in-debug-mode/10705 https://ziggit.dev/t/wasm-index-out-of-bounds-only-in-debug-...
  - pyrolistical 1y ago
    https://github.com/Pyrolistical/zig-wasm-canvas https://github.com/Pyrolistical/zig-wasm-canvas
Anduia 1y ago
Last commit on Jan 29, 2022
s-macke 1y ago
clang can compile into wasm pretty well via the --target=wasm32 option. It creates small binaries. My 16-Bit x86 emulator with BIOS and DOS emulation is under 100kB [0]. [0] https://github.com/s-macke/FSHistory https://github.com/s-macke/FSHistory
- ncruces 1y ago
  And if you need parts of libc, you can use something like the below, for something more minimal than musl: https://github.com/Photosounder/MinQND-libc https://github.com/Photosounder/MinQND-libc Personally, although I do use wasi-sdk (clang) and the wasm32-unknown-wasi triple, the result can be basically free-standing, depending on what flags you use. As a sibling post said, optimization matters, and using wasm-ctor-eval and wasm-opt also helps. But it's useful to keep full C semantics.
  - s-macke 1y ago
    Thanks. This is awesome. For the emulator I wrote my own 200 line libc implementation with a five line malloc routine [0]. Nice to see another implementation, which does a little bit more. [0] https://github.com/s-macke/FSHistory/tree/master/src/wasm_libc_wrapper https://github.com/s-macke/FSHistory/tree/master/src/wasm_li...
  - apitman 1y ago
    > Personally, although I do use wasi-sdk (clang) and the wasm32-unknown-wasi triple, the result can be basically free-standing, depending on what flags you use. This is what I've been doing for my little non-WASI runtime. For my minimal programs I find only a few wasi exports are required, which don't appear to actually be used and I just stub them out. Would love to figure out how to get rid of the code depending on them entirely but it's lower priority.
    - ncruces 1y ago
      If it's possible that it's stuff that's being used at initialization time, wasm-ctor-eval might help. Also, you probably want to build a reactor (-mexec-model=reactor) if that's not what you're already doing. A command will use WASI to read command-line arguments and environment. But it's hard to tell without knowing the specific imports you're trying to get rid of.
teo_zero 1y ago
> here are some of the most commonly used features of C language NOT supported by c4wa. > [...] Almost all new features introduced in C99 At least, it doesn't require K&R syntax for functions!
b0a04gl 1y ago
[dead]
keysdev 1y ago
> It's really, really difficult to recognize out original logic here. Among other things, whereas our original C code only has 2 local variables, this version has 29, not counting module-level globals. Isnt that quite common now with machine generated code. Look at nim clientside js, I dear any js dev to try to navigate that. The point is should we just trust the machine generated as it is and hope that the compiler/bundler just did a correct job, or just write clean and simple code

91 points by 90s_dev 1y ago

In the comparison with Emscripten using wasm-decompile [1], the author appears to have forgotten to turn on optimization. Yes, if you run emcc with no -O option then you will get extremely bad generated code quality, similar to most C compilers. Add -O and you get nice and tight code similar to what c4wa outputs. [1] https://github.com/kign/c4wa/blob/master/etc/doc/comparison.md https://github.com/kign/c4wa/blob/master/etc/doc/comparison....

soegaard 1y ago
I think, the author's goal was to produce wasm-code that had the same structure as the original C. Thus it makes sense to turn off the advanced optimizations.

lioeters 1y ago

> c4wa needs Java 11 or above It sounded good until this part. Would have been nice if it were written in the subset of C that it supports, so it could compile the compiler to Wasm.

apitman 1y ago

This is actually pretty compelling to me. I think the more support for freestanding wasm modules the better. I'm working on a custom wasm app runtime and I don't want to have to implement the entire API surface of Emscripten or WASI. The new component model is even more complex. I wish there was more tooling available for using C/Rust stdlib functions for things like reading files or opening a socket, but being able to define your own API to handle the actually operations in the host/module interface.

pyrolistical 1y ago

Zig can also compile to free standing wasm

jeden 1y ago
any example? I search wasm without js.
- whitehexagon 1y ago
  I noticed this question yesterday, which includes the changed build options for freestanding. https://ziggit.dev/t/wasm-index-out-of-bounds-only-in-debug-mode/10705 https://ziggit.dev/t/wasm-index-out-of-bounds-only-in-debug-...
- pyrolistical 1y ago
  https://github.com/Pyrolistical/zig-wasm-canvas https://github.com/Pyrolistical/zig-wasm-canvas

Anduia 1y ago

Last commit on Jan 29, 2022

s-macke 1y ago

clang can compile into wasm pretty well via the --target=wasm32 option. It creates small binaries. My 16-Bit x86 emulator with BIOS and DOS emulation is under 100kB [0]. [0] https://github.com/s-macke/FSHistory https://github.com/s-macke/FSHistory

ncruces 1y ago
And if you need parts of libc, you can use something like the below, for something more minimal than musl: https://github.com/Photosounder/MinQND-libc https://github.com/Photosounder/MinQND-libc Personally, although I do use wasi-sdk (clang) and the wasm32-unknown-wasi triple, the result can be basically free-standing, depending on what flags you use. As a sibling post said, optimization matters, and using wasm-ctor-eval and wasm-opt also helps. But it's useful to keep full C semantics.
- s-macke 1y ago
  Thanks. This is awesome. For the emulator I wrote my own 200 line libc implementation with a five line malloc routine [0]. Nice to see another implementation, which does a little bit more. [0] https://github.com/s-macke/FSHistory/tree/master/src/wasm_libc_wrapper https://github.com/s-macke/FSHistory/tree/master/src/wasm_li...
- apitman 1y ago
  > Personally, although I do use wasi-sdk (clang) and the wasm32-unknown-wasi triple, the result can be basically free-standing, depending on what flags you use. This is what I've been doing for my little non-WASI runtime. For my minimal programs I find only a few wasi exports are required, which don't appear to actually be used and I just stub them out. Would love to figure out how to get rid of the code depending on them entirely but it's lower priority.
  - ncruces 1y ago
    If it's possible that it's stuff that's being used at initialization time, wasm-ctor-eval might help. Also, you probably want to build a reactor (-mexec-model=reactor) if that's not what you're already doing. A command will use WASI to read command-line arguments and environment. But it's hard to tell without knowing the specific imports you're trying to get rid of.

teo_zero 1y ago

> here are some of the most commonly used features of C language NOT supported by c4wa. > [...] Almost all new features introduced in C99 At least, it doesn't require K&R syntax for functions!

b0a04gl 1y ago

[dead]

keysdev 1y ago

> It's really, really difficult to recognize out original logic here. Among other things, whereas our original C code only has 2 local variables, this version has 29, not counting module-level globals. Isnt that quite common now with machine generated code. Look at nim clientside js, I dear any js dev to try to navigate that. The point is should we just trust the machine generated as it is and hope that the compiler/bundler just did a correct job, or just write clean and simple code