Make cmake script fail when it cannot find certain dependencies

[haampie]

I tried to build this package, but it did not install the kcov binary because cmake couldn't find a couple dependencies.

Could we maybe replace things like

+ find_package (Bfd)
- find_package (Bfd REQUIRED)

for linux so that the kcov executable actually gets built instead of silently ignored?

A popular approach is to introduce variables like USE_BFD and USE_ELFUTILS with sensible defaults, let the user optionally set those, and then do:

if (USE_BFD)
  find_package(Bfd REQUIRED)
endif()

if (USE_ELFUTILS)
  find_package(ElfUtils REQUIRED)
endif ()

[SimonKagstrom]

Well, I did some digging to remember why I did it this way. It's actually issue #83 , because libbfd isn't technically needed even on Linux. It's used for the --verify option. That it doesn't build kcov itself without it seems like a regression, the original intention was to skip just the address verifier library if libbfd isn't available.

That said, I'd be OK to make it mandatory on Linux (and maybe FreeBSD).

[haampie]

Thanks for digging that up :)

I think you can leave it an optional dependency, but allow the user to add a flag like WITH_ADDRESS_VERIFIER=On/Off, and if on, do find_package(... REQUIRED).

That way package managers can explicitly turn it on or off and specify dependencies accordingly

[SimonKagstrom]

But is the problem Linux or OSX here? From the spack issue, it seems like the build issue is on OSX if it finds libbfd?

I'm inclined in simply making libbfd mandatory on Linux/FreeBSD and not looking for it at all on other platforms (i.e., OSX).

[haampie]

Ah, in spack elfutils and libiberty etc were not listed as dependencies which caused kcov to be skipped for me, so I added those. Somehow that is not the case on macos, so someone else removed them for macos.

[SimonKagstrom]

Yes, the kcov-system-daemon can be built separately from the rest without those dependencies. I guess it hasn't been used by anyone other than myself, so perhaps it's time to enforce some of it.

Anyway, I pushed libbfd being required for Linux+FreeBSD, so hopefully it will work betetr after that.

[jonhoo]

@SimonKagstrom Note that libbfd (unlike elfutils) is GPLv3, which means that kcov now requires GPLv3-licensed libraries to link and run, which are often not available in commercial settings, making kcov v39 hard to use in such contexts.

[SimonKagstrom]

Yes, that is true. I guess it would be better to make it non-required again.

It will be missing the --verify functionality then though, which does help a lot (especially it seems for Rust binaries).

[jonhoo]

Yeah, it is unfortunate, since --verify is super handy, but better to have some (hard to debug) access to coverage than none :sweat_smile: