Track a distinct compile cache for julia-debug.

[twadleigh]

Addresses #33668.

[twadleigh]

JLOptions().debug_level > 1 is my best guess for the most robust way to test for julia-debug, but others much more knowledgeable may have a different opinion.

[twadleigh]

Specifically, I chose to prefer it to something like:

endswith(basename(unsafe_string(Base.JLOptions().julia_bin)),"-debug")

so as to be insensitive to a name change of the executable.

[vchuravy]

JLOptions().debug_level corresponds to the -g option and not whether the binary was build with debug information embedded

[twadleigh]

Yes, the test should be ccall(:jl_is_debugbuild, Cint, ()) > 0.

[tkf]

FYI an alternative implementation may be to include JLOptions().julia_bin in package_slug. I implemented this in #29914:

julia/base/loading.jl

Lines 136 to 141 in fa5f1b1

	function package_slug(uuid::UUID, p::Int=5)
	crc = _crc32c(uuid)
	crc = _crc32c(unsafe_string(JLOptions().image_file), crc)
	crc = _crc32c(unsafe_string(JLOptions().julia_bin), crc)
	return slug(crc, p)
	end

A major advantage might be that using JLOptions().julia_bin (and .image_file) would support differentiating arbitrary binaries which are not precompile-cache -compatible. A disadvantage is that renaming the binary would create a different set of precompile-cache files. However, this can be avoided by symlinking julia/julia-debug binary.

[twadleigh]

@tkf, different system images similarly clobber the compile cache? Tweaking the slug is one way to go. You might also consider qualifying the path, like I did here. It might be a more palatable solution to the maintainers, as it is guaranteed not to interact with the existing implementation.

[tkf]

different system images similarly clobber the compile cache?

Yes, especially because you can use PackageCompiler to bundle a different set of packages in the system image.

You might also consider qualifying the path

Yes, using suffix as you do in this PR does have a benefit like refreshing precompilation cache is as easy as rm -r ~/.julia/compiled/v1.x-debug and does not slow down normal julia usage.

[twadleigh]

@tkf, I think I'll attempt a modest extension of this solution that would, for instance, keep the caches distinct for distinct build images.

[tkf]

@twadleigh I actually don't know how much core devs want to play with it. So maybe just wait for a response? I don't want to request a feature that would be rejected by core devs :)

[twadleigh]

@tkf, fair enough. I'll propose an extension in a separate PR only if/when this is merged.

[tkf]

FYI, @KristofferC just merged PR #29914. I'm not sure @KristofferC was aware of this patch. Sorry, I should have mentioned there that an alternative patch was suggested in this PR...

[twadleigh]

@tkf, I'll close this. If it turns out master still doesn't have the functionality I'm looking for, I'll reopen.