Running without a proc mount fails with `FileNotFound`

[arthurmelton]

Zig Version

0.14.0-dev.1951+857383689

Steps to Reproduce and Observed Behavior

The easiest way is to to chroot into an environment without any /proc mount. Fails trying to read /proc/self/exe, when trying to get the exe folder for finding the lib folder.

Expected Behavior

I don't actually know if this should continue working this way and require the /proc mount, and give a better error message than just error: FileNotFound, or if this should try to do some funkiness if the /proc mount does not exist. gcc does not require the /proc mount, and its pretty nice for testing building in limited environments.

[rohlem]

its pretty nice for testing building in limited environments.

There is already a CLI option for specifying the lib dir path explicitly, from zig build-exe --help:
--zig-lib-dir [path] Override path to Zig installation lib directory

I assume this should work around that error to enable that usage scenario (not sure whether that correctly works though).
There's similar options --cache-dir and --global-cache-dir, if those lead to similar issues.
Once that works, the compiler should probably mention these CLI arguments in a bespoke error message rather emitting the plain error: FileNotFound.

[arthurmelton]

So, doing some looking it looks like you can't do zig build --help, as that gives the unhelpful error, but zig build-exe --help response as usual. If I try doing zig build-exe --zig-lib-dir /lib/zig/ src/main.zig, we are getting closer as it says a good error now error: unable to find zig self exe path: FileNotFound. I am confused if there is maybe another reason for it needing to know its own exe path, after being provided the lib dir. Providing the cache dir, gives the same error as if it was not provided.

[andrewrk]

Bug report is missing Steps To Reproduce. If provided I will re-open

[arthurmelton]

So for the Steps To Reproduce, I will show a more realistic example using an alpine linux mini rootfs. The main idea is to follow this idea.

• Make some mnt folder where a fake rootfs will be put into.
• Download the alpine linux mini rootfs and extract it into the mnt folder.
• Download and install Zig inside the mnt folder.
• Chroot into the mnt folder and attempt to use zig.

This is how we can setup what I described, except chrooting into the environment (shown for x86_64).

mkdir mnt
cd mnt
wget https://dl-cdn.alpinelinux.org/alpine/v3.20/releases/x86_64/alpine-minirootfs-3.20.3-x86_64.tar.gz
tar -xzf alpine-minirootfs-3.20.3-x86_64.tar.gz
rm alpine-minirootfs-3.20.3-x86_64.tar.gz
wget https://ziglang.org/builds/zig-linux-x86_64-0.14.0-dev.2097+d30e28754.tar.xz
tar -xf zig-linux-x86_64-0.14.0-dev.2097+d30e28754.tar.xz
rm zig-linux-x86_64-0.14.0-dev.2097+d30e28754.tar.xz
mv zig-linux-x86_64-0.14.0-dev.2097+d30e28754/lib usr/lib/zig
mv zig-linux-x86_64-0.14.0-dev.2097+d30e28754/zig usr/bin/
rm -r zig-linux-x86_64-0.14.0-dev.2097+d30e28754/
cd ..

After you have setup everything you can chroot into the environment

sudo chroot mnt/ /bin/sh

Once you are in you can attempt to init a project and it will fail

mkdir -p /root/project
cd /root/project
zig init # Fails

You can get out of the environment by just typing exit. To make zig work you have to do (don't forget to umount mnt/proc, after you exit the chroot, because if you try to rm -rf mnt, this will cause some problems on your system.)

sudo mount --types proc /proc mnt/proc

Now if we chroot into the environment again, the zig init command will not fail anymore.

[arthurmelton]

@andrewrk Could this get reopened with the new steps to reproduce, or do I need to edit the original message and put them there?