BTW there is also one use for symbol versioning that's semi-legitimate and not related to mixing ABIS; I believe glibc makes use of this. If you have a family of related shared libraries and want to provide some symbols for private interfaces between them, you can use a non-default version. This prevents the symbol from being linkable by ld without specifying a specific version (e.g. so configure scripts won't detect the presence of the symbol)

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