Should we build with STL and/or ABSEIL support?

[kkraus14]

Comment:

Looks like we're currently not building with STL or Abseil support. At least enabling STL would be an ABI break so we should probably wait until a patch version to prevent breaking folks if we want to enable it.

See:

• abseil: https://github.com/open-telemetry/opentelemetry-cpp/blob/v1.6.0/api/CMakeLists.txt#L44
• STL: https://github.com/open-telemetry/opentelemetry-cpp/blob/v1.6.0/api/CMakeLists.txt#L55

[kkraus14]

Looks like abseil usage is only if you're not using STL: https://github.com/open-telemetry/opentelemetry-cpp/blob/v1.6.0/api/include/opentelemetry/nostd/variant.h

So really this is just if we should use the STL or not.

[h-vetinari]

We can probably build with abseil and get two bird with one stone (since on C++17, abseil will already mostly use STL for its types).

[kkraus14]

We can probably build with abseil and get two bird with one stone (since on C++17, abseil will already mostly use STL for its types).

Abseil is a non-trivial dependency with less than ideal versioning where I'd be -1 on making that the default build.

[h-vetinari]

Meh, it's already everywhere (including now protobuf's API). 🤷

Especially as I expect most users of this lib to come through arrow, which already depends on abseil.

[h-vetinari]

Abseil is a non-trivial dependency with less than ideal versioning where I'd be -1 on making that the default build.

As of #48, opentelemetry will depend on abseil (through protobuf 4.x), so this point is moot. Not sure if we gain anything by flipping WITH_ABSEIL though? CC @lidavidm

[lidavidm]

Yeah, and additionally they've said upstream that C++17 support effectively requires WITH_STL.

From a quick search, the flag still configures whether it tries to link some abseil libraries into OTel. But it's overridden in the source itself via ifdefs, so I say it's a pointless flag and we just use WITH_STL.

(Also, if you don't use WITH_STL and don't use WITH_ABSEIL, it just pulls a vendored copy anyways. 🤦)

[h-vetinari]

Yeah, and additionally they've said upstream that C++17 support effectively requires WITH_STL.

Well, that's because at C++17, abseil effectively delegates everything to the stdlib. So I think I'll stay with abseil for now, because it should have a superset of capabilities than what the stdlib offers (happy to be corrected though if I'm wrong on this).

(Also, if you don't use WITH_STL and don't use WITH_ABSEIL, it just pulls a vendored copy anyways. 🤦)

Yeah, I noticed, which is why we're getting symbol collisions now that abseil is on the library path. We have to bite the bullet anyways.