Limiting the scope of global symbols from linked objects
c, c++, gcc, static-linking, unix-ar
Solution
You can manually remove unneeded symbols on the final combined library:
`$ objcopy -N foo cppwrap.a` (remove symbol)
Or, if you need the symbols but want to make sure that external users can't get to them:
`$ objcopy -L bar cppwrap.a` (localize symbol)
Or, if a symbol in `clib.a` must be visible by something in `cpp.o` but you don't want it to be used by anyone else:
`$ objcopy -W baz cppwrap.a` (weaken symbol)
In this case, collisions with symbols from other object files/libraries will defer to their usage, even though the symbol will still be visible. To obscure things further or to reduce chances of even a deferential collision, you can also use:
`$ objcopy --redefine-sym old=new cppwrap.a`
An anonymous namespace may help in some cases, but not if there's functionality that your wrapper needs but is trying to hide from external users.
Problem
I have a C library in an archive file, `clib.a`. I've written a C++ wrapper for it, `cpp.o`, and would like to use this as a static library: ``` ar cTrvs cppwrap.a clib.a cpp.o ``` Code which links to this won't be able to use the stuff from `clib.a` directly unless the correct header is included. However, if someone coincidentally creates an appropriate prototype -- e.g. `void myCoincidentallyNamedGlobalFunction()` -- I'm concerned which definition of `myCoincidentallyNamedGlobalFunction` will apply. Since the symbols from `clib.a` only need to be accessed in `cpp.o`, and not anything linked to `cppwrap.a`, is there a way to completely hide them so that there is no possible collision (so even including the clib header would fail)?