So you think you know C? | Hacker News Reader

So you think you know C?

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22 pointspjmlp9 comments

I can't answer to the C spec, because so much is left undefined, but I can answer some to GCC and tcc, and that tells me that though these are contrived examples, I've encountered at least some of these in the wild.

I can't wait till rustc prodyces smaller executables so I can switch to it.

I believe rustc produces pretty small executables if you allow it to dynamically link libstd. C gets two advantages over Rust, one fair and one slightly unfair: it has a stable binary ABI, and the standard C library is already installed everywhere. If you're using Rust for internal use, you can probably figure out a distribution mechanism for every libstd version in use, because you probably only have very few in use at any given time, and you can rustc -C prefer-dynamic. (For instance, Debian in fact builds a normal library package for each libstd for each compiler release they package, which would probably work.)

Unfortunately dynamic doesn't work for me.

I use musl day-to-day to cross compile statically linked executables, which tend to be 1500kb or so. (Embedded systems with around 10mb of memory or less).

I used to bash glibc into compliance, and musl was like a gift from heaven.

Unfortunately rustc isn't there yet - though it is on the radar for the future.

Have you seen that rustup makes using musl with rustc really easy [0]? One can then additionally forgo things like the optimised jemalloc allocator and the main standard library (just using libcore) to knock the binary size down to what C gives. [0] discusses this in much more detail (especially towards the end).

[0]: https://blog.rust-lang.org/2016/05/13/rustup.html#example-bu...

[1]: https://lifthrasiir.github.io/rustlog/why-is-a-rust-executab...

> Today rustup provides access to the standard library, but as we’ve seen in this post, there’s more to cross-compilation than rustc + std. It’s acquiring and configuring the linker and C toolchain that is the most vexing

Unfortunately I'd have to agree with this, C is just easier.

> We have knocked debug symbols down, now let’s get rid of the remaining libraries. Some bad news: From this point on you are entering the realm of nightly Rust. This realm is not as scary as you might think, as it doesn't break in your face, but it may break in smaller ways (which is why we have nightlies!). That’s the major reason that we don’t yet have nightly features in stable– they may change.

Relying on a nightly for production code is simply not something I would ever get approved.

I sort of hope that as Rust solves these issues, tools like rustup and Cargo will get to the state of Red and its cross-compilation state. (Compile for Linux-86, Linux-ARM, Windows, macOS, Android with one flag from the one compiler. Which is less than 1mb, statically linked.)

This basically sez 'Don't assume a specific answer when something is undefined'. As long as you don't, and experienced C programmers don't, then what is the big deal?

> experienced C programmers don't

C leaves a lot undefined. These were tiny examples, and many were undefined for more than one reason. Experienced C programmers rely on undefined behavior all the time: http://www.metzdowd.com/pipermail/cryptography/2015-October/....

Close but not correct. Some are undefined. Some are implementation defined. Some are different between different versions of C.

The answer to #3 is a compiler error. char a = ‘ ‘ * 13; is not a valid line of C, the compiler will fault for having a left single quotation mark in the line.

The author or Medium corrupted their line of C with pretty printing operations.

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