`./mach check` fails on Fedora 26: src/task_info.c:10:10: fatal error: mach/mach_init.h: No such file or directory

[jonleighton]

As of e2f534f I can no longer run ./mach check on Fedora 26. Here is the output of `./mach check -v'. The error is:

running: "cc" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-g" "-m64" "-o" "/home/turnip/Code/servo/target/debug/build/task_info-5b509507e8510095/out/src/task_info.o" "-c" "src/task_info.c"
cargo:warning=src/task_info.c:10:10: fatal error: mach/mach_init.h: No such file or directory
cargo:warning= #include <mach/mach_init.h>
cargo:warning=          ^~~~~~~~~~~~~~~~~~
cargo:warning=compilation terminated.

It comes from the support/rust-task_info crate, but I think what has happened is that before e2f534f, task_info wasn't being built (it doesn't show up in the output of ./mach check -v on the preceding commit). The change in e2f534f seems to have made it so that ./mach check does now try to build task_info, and so the failure is now showing up.

It appears that the code in the task_info crate is targeted at OS X, which would be why it won't build for me. I've tried to do a bit of figuring out about why ./mach check is now trying to build it when it previously didn't, but I haven't got very far.

./mach build seems to work fine, so this just affects the check command.

cc @asajeffrey

[jonleighton]

Aha, we should only be use-ing the task_info crate on macos anyway:

servo/components/profile/mem.rs

Lines 368 to 369 in bcdb82b

	#[cfg(target_os = "macos")]
	use task_info::task_basic_info::{virtual_size, resident_size};

So it seems like the conditional compilation attribute is not working properly on this earlier version of rustc.

[jonleighton]

I tried to find a Rust commit/issue relating to this, but failed

[SimonSapin]

This likely regressed in #19574 , which downgraded the compiler to work around a compiler bug but unfotunately downgraded Cargo at the same time. We can upgrade again when we find a proper fix for #19519.

In the meantime, try ./mach check -p servo.

[asajeffrey]

Oh great. AFAICT there is currently no rustc version which can build servo successfully. We either hit this bug or #19519, sigh.

[jonleighton]

Note that it only affects ./mach check, not ./mach build, so the status quo isn't a total disaster

[SimonSapin]

I just checked, ./mach check -p servo works.