Versioned Symbols in Shared Libraries

[Maurizio Cimadamore]

Hi Sebastian,
Sadly, `dlopen` only does unversioned lookups (unless you use some 
tricks, like the RTLD_NEXT pseudo handles, which we don't use). On *nix 
systems another primitive for looking up symbols exists, namely `dlvsym` 
which takes an extra string pointer (the version).

So, I think your best bet would to create your own SymbolLookup which 
can be initialized with a given version number, which is then passed to 
calls to `dlvsym`.

Since this capability doesn't make sense on platforms other than GCC (I 
believe), adding support for versioning in SymbolLookup itself would 
seem a bit odd.

Maurizio

On 29/09/2022 12:49, Sebastian Stenzel wrote:
> Hi,
>
> Today I learned about versioned symbols when investigating a downwards compatibility problem in a jextract'ed API. See discussion [1]
>
> The concept is new to me, but apparently broadly used to make sure to invoke the exact function that was referenced at compile time. Since jextract only knows the header files, I suppose it isn't aware of such versions? Does the SymbolLookup API provide any mechanism to lookup a specific version?
>
> I hope you can make sense of what I'm asking as this is all new to me and I'm not sure I'm asking the right questions.
>
> Thank you!
>
> [1]: https://github.com/libfuse/libfuse/discussions/701