replace /bin/bash shebang with /usr/bin/env bash

[oliverlee]

This allows systems which don't have this location (e.g. NixOS) to run the scripts.

[oliverlee]

I suppose the failures are related to this, but I am not familiar with rules_rust:

toolchains_llvm/toolchain/osx_cc_wrapper.sh.tpl

Lines 165 to 167 in 0bdeae2

	# calling this script, which would make /usr/bin/ld unreachable. For example,
	# rules_rust does not set PATH (unless the user explicitly sets PATH in env
	# through attributes) [1] when calling rustc, and rustc does not replace an

[RyanTorok]

As you mostly pointed out already, using /usr/bin/env is a double-edged sword. On one hand, it's guaranteed to exist on all POSIX-compliant systems, so it will be present on, e.g. NixOS. On the other hand, it's entirely reliant on what the calling ruleset puts in $PATH.

I'm not too familiar with the internals of rules_rust either, but based solely on the comment you tagged above, it appears that rules_rust doesn't add /usr/bin to $PATH, which means /usr/bin/env won't find /usr/bin/bash, even though the latter exists.

I'm not sure if this is the cleanest solution possible, but if you really need bash for these scripts, you might consider having a small wrapper script that uses #!/bin/sh (which is required to exist on POSIX-compliant systems) and searches manually for the right shell. You could default to /bin/bash and then fall back to /usr/bin/env bash if the former doesn't exist. Then just invoke the existing script using the shell you find.

Hope this helps!

[fmeum]

Would it be possible to rewrite these scripts so that they only require /bin/sh? Some of them are only relevant for development and could just use /usr/bin/env bash.

[RyanTorok]

It's really only the two cc_wrapper scripts that matter. Keeping the test scripts as #!/bin/bash is probably fine, unless you're planning on running CI on a non-FHS platform. The only other script besides those is llvm_checksums.sh, which should almost always be run manually, so it's also not a major issue.

I think rewriting the two cc_wrapper scripts to support #!/bin/sh seems like a reasonable choice. Note that different platforms use a different shell in the role of /bin/sh, e.g. many Linux distros including Ubuntu now use dash instead of bash as /bin/sh. Limiting the script to POSIX-standard features should hopefully avoid future headaches.

[oliverlee]

Thanks for your comments.

It's really only the two cc_wrapper scripts that matter.

Probably only toolchain/cc_wrapper.sh.tpl matters. If toolchain/osx_cc_wrapper.sh.tpl is only used on macOS, we can probably assume /bin/bash exists.

I'm not sure I'll have time to look into this in the near term, so feel free to take over if you're interested.