Undefined symbol when building with address sanitizer

[Ky Waegel]

I've been working to build Protobuf with ASan and/or UBSan support (mostly for compatibility with a containing project), and I've been running into some weird symbol visibility errors. Example trying to run `protoc` with "-fsanitize=address" enabled:

protobuf-27.1/libprotoc.so.27.1.0: undefined symbol: _ZTIN2pb11CppFeaturesE

I initially thought this was just a weird quirk in my build system, but then I discovered this patch to a vendored copy of Protobuf inside of MySQL 8.4.0 that reference the same symbol, mentions that the change is required for UBSan support, and fixes my symbol issue.

Anyone know what's going on here? Asking here before filing a bug because I'm not entirely sure if this is a bug, or of I'm (ab)using the build flags somehow.

(Initially ran into this with v24.3, but the same thing happens with v27.1.)

[Adam Cozzette]

Does putting an asterisk in front of pb::* here fix the problem? I think we're trying to export everything under the pb namespace, but for some reason the type info for pb::CppFeatures is not getting exported.

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[Ky Waegel]

Yes, using *pb::*; seems to fix the issue. Would that be a more appropriate change if I'm trying to patch the copy I'm building?

[Ky Waegel]

Yes, that seems to work.

On Friday, June 7, 2024 at 2:50:24 PM UTC-7 Adam Cozzette wrote:

[Adam Cozzette]

Great, that should be a safe change to patch then. I submitted this today here, but it will take some time for that change to make it into a release.

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