Should we include commented-out libcore in avr-rust?

[dylanmckay]

I was wondering what your thoughts were @shepmaster and @gergoerdi on pushing one of the minified versions of libcore you both have so that it is a part of this repo?

There isn't much point in maintaining separate local libcore libraries.

One concern is that it may mean that we get more merge conflicts. We would probably have to comment out parts of libcore in this repository anyway for stuff like float/libcore support.

[gergoerdi]

My version is here: https://github.com/gergoerdi/rust-avr-libcore-mini I'm happy to move it wherever. It is based on libcore as of e80f644 with the following modules (and references to them) removed:

• any.rs
• cell
• char
• char_private
• fmt::*
• hash::*
• num::{bignum, dec2flt, flt2dec, diy_float}
• raw
• slice::sort
• str
• sync::*
• tuple

[shepmaster]

The big trick to me is that we need the full libcore to build the compiler for the host but when targeting AVR we need the minimized libcore for now.

Commenting out wouldn't be sufficient for that, unless we actually had two directories, at which point the merge conflicts would go to zero but the updating process would get much harder ;-)

Perhaps #[cfg(not(target_arch = "avr"))] (or whatever is the real value) would be better than commenting out stuff. Would also be good markers for use to remove as we go along.

Beyond that, I'd be happy to see it present here.

[shepmaster]

As a rough scope:

$ diff --unified -r libcore/ rust-avr-libcore-mini/src/ | wc
    2084    8801   68577

This includes changes like

-#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Debug, Hash)]
+#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd)]

Which I'm sure was annoying to do and will be annoying to bracket in cfg blocks.

[shepmaster]

I feel like most of the Debug and formatting differences would be taken care of by #37, which is why I'd be more excited to see that fixed instead of commenting out every Debug implementation.

[gergoerdi]

In the meantime, couldn't we reduce the diff considerably by keeping Debug and Hash and just stubbing them out, instead of removing them? Let me try and see how it'd work.

[gergoerdi]

I've got great news! I've just pushed a new version of libcore-mini (overwriting master) that is almost identical to the real libcore, but still works well enough that I can compile my CHIP-8 program with it:

19:05:56 [cactus@galaxy src]$ diff -ur $CORE .|wc
    957    4306   33726

[gergoerdi]

The remaining changes compare to libcore are, I believe, rather benign and concentrated (no more "I had to remove Hash and Debug derivation from every. single. type.")

• Float and i128/u128 support is removed
• All the panicking macros just loop{}
• The sync module is removed (I haven't investigated yet why this is needed)
• Most of the fmt module is stubbed out
• String <-> number conversion is removed

[gergoerdi]

19:22:23 [cactus@galaxy src]$ diff -qr $CORE .
Only in /home/cactus/prog/rust/rust-avr/rust/src/libcore: Cargo.toml
Only in /home/cactus/prog/rust/rust-avr/rust/src/libcore: benches
Files /home/cactus/prog/rust/rust-avr/rust/src/libcore/fmt/mod.rs and ./fmt/mod.rs differ
Files /home/cactus/prog/rust/rust-avr/rust/src/libcore/fmt/num.rs and ./fmt/num.rs differ
Files /home/cactus/prog/rust/rust-avr/rust/src/libcore/iter/range.rs and ./iter/range.rs differ
Files /home/cactus/prog/rust/rust-avr/rust/src/libcore/lib.rs and ./lib.rs differ
Files /home/cactus/prog/rust/rust-avr/rust/src/libcore/macros.rs and ./macros.rs differ
Files /home/cactus/prog/rust/rust-avr/rust/src/libcore/num/mod.rs and ./num/mod.rs differ
Files /home/cactus/prog/rust/rust-avr/rust/src/libcore/num/wrapping.rs and ./num/wrapping.rs differ
Files /home/cactus/prog/rust/rust-avr/rust/src/libcore/panicking.rs and ./panicking.rs differ
Files /home/cactus/prog/rust/rust-avr/rust/src/libcore/str/mod.rs and ./str/mod.rs differ
Only in /home/cactus/prog/rust/rust-avr/rust/src/libcore: tests

[gergoerdi]

More details on the magnitude of the difference from upstream libcore:

 src/fmt/mod.rs      | 310 ++--------------------------------------------------
 src/fmt/num.rs      |   6 +-
 src/iter/range.rs   |   1 -
 src/lib.rs          |   9 +-
 src/macros.rs       |   9 +-
 src/num/mod.rs      | 282 +----------------------------------------------
 src/num/wrapping.rs |   2 +-
 src/panicking.rs    |  12 +-
 src/str/mod.rs      |  27 +----
 9 files changed, 26 insertions(+), 632 deletions(-)