book should mention crates.io in FFI chapter

[durka]

If you blindly copy the example code from the FFI chapter you get the "libc is unstable" warning.

[durka]

Ugh... so the examples have a hidden #![feature(libc)] line, so you'll see that if you click through to the playpen. I see why it's done that way (so the examples are runnable) but it seems bad, pedagogically. Thoughts?

[steveklabnik]

The issue is, normally, you want to copy the code exactly, and put libc in your cargo.toml. That's why I hid it.

[durka]

Yeah, that makes sense. So maybe just a mention at the beginning about putting libc in Cargo.toml. And maaaybe another sentence about how if you click the examples some extra lines get inserted to make it compile in the playpen? (About half of them don't compile anyway since they refer to nonexistent libraries, though this could be fixed with even more hidden lines containing #[cfg] trickery.)

[steveklabnik]

👍

[durka]

Fun bash ...thing to pull code blocks out of a Markdown file and try compiling them:

for block in $(grep -n '```' src/doc/trpl/ffi.md | paste -s -d ':\n' - | grep 'rust\|no_run')
do
    from=$(echo $block | cut -d: -f1);
    to=$(echo $block | cut -d: -f3);
    f=$(mktemp /tmp/doctest.XXX);
    head -$((to - 1)) src/doc/trpl/ffi.md | tail -$(($to - $from - 1)) | sed 's/^# //' >$f;
    mr ru nightly rustc $f >/dev/null 2>&1 && rm doctest;
    echo $from $?;
    rm $f;
done

[steveklabnik]

rustdoc --test path/to/markdown will do that already :)

[durka]

Oh, how about that :)

[durka]

Does that not try linking? 'Cause it says everything passes but my bash script disagrees.