CODEWITHSUNDEEP
cinterfacelinker
Piotr
Piotr

Reputation: 542

Hiding a library within a library

Here's the situation. I have an old legacy library that is broken in many places, but has a lot of important code built in (we do not have the source, just the lib + headers). The functions exposed by this library have to be handled in a "special" way, some post and pre-processing or things go bad. What I'm thinking is to create another library that uses this old library, and exposes a new set of functions that are "safe".

I quickly tried creating this new library, and linked that into the main program. However, it still links to the symbols in the old library that are exposed through the new library.

One thing would obviously be to ask people not to use these functions, but if I could hide them through some way, only exposing the safe functions, that would be even better.

Is it possible? Alternatives?

(it's running on an ARM microcontroller. the file format is ELF, and the OS is an RTOS from Keil, using their compiler)

[update]

Here's what i ended up doing: I created dummy functions within the new library that use the same prototypes as the ones in the old. Linked the new library into the main program, and if the other developers try to use the "bad" functions from the old library it will break the build with a "Symbol abcd multiply defined (by old_lib.o and new_lib.o)." Good enough for government work...

[update2] I actually found out that i can manually hide components of a library when linking them in through the IDE =P, much better solution. sorry for taking up space here.

Upvotes: 2

Views: 257

Answers (2)

R.. GitHub STOP HELPING ICE
R.. GitHub STOP HELPING ICE

Reputation: 215257

If you're using the GNU binutils, objcopy can prefix all symbols with a string of your choice. Just use objcopy --prefix-symbols=brokenlib_ old.so new.so (be careful: omitting new.so will cause old.so to be overwritten!)

Now you use brokenlib_foo() to call the original version of foo().

Upvotes: 1

apmasell
apmasell

Reputation: 7153

If you use libtool to compile and link the library instead of ld, you can provide -export-symbols to control the output symbols, but this will only work if your old library can be statically linked. If it is dynamically linked (.so, .dylib, or .dll), this will not be possible.

Upvotes: 1

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