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jank is C++

(jank-lang.org)
252 points Jeaye | 1 comments | 11 Jul 25 17:22 UTC | HN request time: 0.211s | source
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johnnyjeans ◴[11 Jul 25 18:29 UTC] No.44535498[source]▶
I'm not surprised to see that Jank's solution to this is to embed LLVM into their runtime. I really wish there was a better way to do this.

There are a lot of things I don't like about C++, and close to the top of the list is the lack of standardization for name-mangling, or even a way mangle or de-mangle names at compile-time. Sepples is a royal pain in the ass to target for a dynamic FFI because of that. It would be really nice to have some way to get symbol names and calling semantics as constexpr const char* and not have to deal with generating (or writing) a ton of boilerplate and extern "C" blocks.

It's absolutely possible, but it's not low-hanging fruit so the standards committee will never put it in. Just like they'll never add a standardized equivalent for alloca/VLAs. We're not allowed to have basic, useful things. Only more ways to abuse type deduction. Will C++26 finally give us constexpr dynamic allocations? Will compilers ever actually implement one of the three (3) compile-time reflection standards? Stay tuned to find out!

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plq ◴[11 Jul 25 19:11 UTC] No.44535873[source]▶
> the lack of standardization for name-mangling

I don't see the point of standardizing name mangling. Imagine there is a standard, now you need to standardize the memory layout of every single class found in the standard library. Without that, instead of failing at link-time, your hypothetical program would break in ugly ways while running because eg two functions that invoke one other have differing opinions about where exactly the length of a std::string can be found in the memory.

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1. johnnyjeans ◴[11 Jul 25 20:12 UTC] No.44536380[source]▶
The naive way wouldn't be any different than what it's like to dynamically load sepples binaries right now.

The real way, and the way befitting the role of the standards committee is actually putting effort into standardizing a way to talk to and understand the interfaces and structure of a C++ binary at load-time. That's exactly what linking is for. It should be the responsibility of the software using the FFI to move it's own code around and adjust it to conform with information provided by the main program as part of the dynamic linking/loading process... which is already what it's doing. You can mitigate a lot of the edge cases by making interaction outside of this standard interface as undefined behavior.

The canonical way to do your example is to get the address of std::string::length() and ask how to appropriately call it (to pass "this, for example.)