Makefile echo portability across Linux distributions

[benjamin051000]

From canonical/kernel-docs#38, it appears that different distros use different symlinks for sh, which can affect the way echo behaves.

More information about non-portable echo behavior can be found here: https://unix.stackexchange.com/questions/700675/why-is-echo-e-behaving-weird-in-a-makefile

We should try to make this portion of the makefile more portable, although I'm not sure how.

One potential way we could solve this is by adding SHELL = bash in the Makefile, which forces it to use bash's echo (technically requires bash, but nearly all distros ship with bash these days). This would require us to add -e to each instance of echo where newlines may be printed.

What should we do?

[benjamin051000]

This would work:

BASH_FLAG=""
ifeq ($(shell basename $(shell realpath $(SHELL))), bash):
    ECHO_FLAGS="-e"
endif

# ...

help:
    @echo $(BASH_FLAG) "..."

This would prevent requiring one particular shell. This works on my distro (openSUSE TW). It correctly sets -e as the flag.

One annoying thing is you now need to write @echo $(BASH_FLAG) everywhere now... maybe it's possible to make a .PHONY echo target that calls system echo with the flag, a la wrapper function?

[SecondSkoll]

Is there a reason why we shouldn't pivot to printf? The only things we do with echo are newlines and a a couple of variable replacements (with regular characters, so unlikely to do anything funky).

[benjamin051000]

@SecondSkoll I'm not an expert, but online sentiment (e.g., on above stackexchange pages) seems to be that printf is more portable. This could be a solution.

[SecondSkoll]

I think moving to printf will probably be easier. I'm also no expert, so we'll just continue trying to support people as best we can. I'll get something merged in soon. :)