This is the mail archive of the email@example.com mailing list for the gas2 project.
|Index Nav:||[Date Index] [Subject Index] [Author Index] [Thread Index]|
|Message Nav:||[Date Prev] [Date Next]||[Thread Prev] [Thread Next]|
That turns out not to be the case. A shared library is not like an archive library. A shared library is a single object. Everything that composes a shared library is linked together. There is only one set of symbols. There is no way for the linker to form any sort of transitive closure operation, because there is no longer any distinction between the various object files which compose the shared library. Although this may be how things work now, it is not really a useful way for things to work. Dividing an ordinary library into separate members provides two benefits: * The members you don't refer to, do not take up space in your program. * The members you don't refer to, do not fill up your program's name space. The first benefit is not relevant or possible when using a shared library, but the second is completely applicable. Linking with a shared library should give you exactly the same external symbols that you would get by linking against the unshared library it was made from. Even if other people's shared library implementations don't do this right, ours should do it right. Doing this right does not require any changes in the shared library run-time mechanism. It only requires some way of representing, in the shared library's symbol table, a division of external symbols into various "library members". Then ld can treat as weak any external definitions which are not in the same "library members" as some symbol that is referenced. Each "library member" should have references as well as definitions; that way, ld can tell that if "library member" A is referenced, and it references member B, then the definitions in B are not weak. With an open-ended format such as ELF, it should not be hard to design a way of representing this information, which does not conflict with anything else and will not confuse other linkers. If ld finds this data, it should act accordingly; otherwise, it should do what it does now. That way, each of our tools is upward compatible. This will make it possible to turn any unshared library into a shared library, with no special precautions, and get no change in the behavior except for sharing of memory. Since ELF is the format that GNU systems use, it is not crucial to implement this in formats other than ELF. Would the people who work on ld please respond?