This is the mail archive of the mailing list for the binutils project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: Stupid question: linking with a symbol under a different name

Thank you for informative answer.

I know about "objcopy --redefine-sym", it can't  be applied here.

The fact is that in general main.o may need to be linked with several *.so files. And these *.so files may have name conflicts (export different symbols under the same name). That's actually the main reason why linking with a symbols under different names seems to be must-have feature.

For example:

I'm given main.o (with unresolved symbols: symbolA, symbolB, symbolC1, symbolC2, symbolD, symbolE).

I'm given libused.o (with exported symbols: symbolA, symbolB, symbolC).

I'm given libsecond.o (with exported symbols: symbolC, symbolD, symbolE).

    I'm given recipe:
- map symbolA (from main.o) to symbolA (from [names coincide]; - map symbolB (from main.o) to symbolB (from [names coincide]; - map symbolC1 (from main.o) to symbolC (from [names differ]; - map symbolC2 (from main.o) to symbolC (but from [names differ]; - map symbolD (from main.o) to symbolD (from [names coincide]; - map symbolE (from main.o) to symbolE (from [names coincide].
      [Note that and both export symbolC.]

So, applying "objcopy --redefine-sym" to main.o is possible, but it doesn't solve name conflict and thus doesn't help here. While applying "objcopy --redefine-sym" to *.so files isn't possible at all, because: (1) it would be different shared library, while linking to original is required; (2) objcopy doesn't work with dynamic symbols (it affects output of "objdump -t", not "objdump -T").

Anyway, thanks for your answer. It could be very helpful if libused and libsecond were static libraries (*.a), not shared (*.so). That's actually the way I use to solve the same problem with static libraries.

[Sorry for duplicate, first reply was accidentally sent to wrong address.]

On 08.10.16 17:23, Rayson Ho wrote:
Sasha ,

Did you try the objcopy command's "--redefine-sym" option??

--redefine-sym old=new
    Change the name of a symbol old, to new. This can be useful when
one is trying link two things together for which you have no source,
and there are name collisions



Open Grid Scheduler - The Official Open Source Grid Engine

On Sat, Oct 8, 2016 at 7:06 AM, Sasha Unknown <> wrote:
It's even more complex. I actually don't have any info about what that
symbol is and what convention it follows (except output of objdump, of

The full task is probably like that:

     I'm given main.o (with some unresolved symbols).

     I'm given (with some exported symbols).

     I'm given recipe, like:
       - map symbol1 (from main.o) to symbol1 (from [names
       - map symbol2 (from main.o) to symbol2 (from [names
       - map symbol3 (from main.o) to symbol862 (from [names
- map symbol4 (from main.o) to symbol5837 (from [names
       - map symbol5 (from main.o) to symbol5 (from [names
       - ...


[Sorry for duplicate, first reply was accidentally sent to wrong address.]

On 06.10.16 23:00, Sasha Unknown wrote:

1. This is possible only with function. If it's a variable, I can't create "wrapper variable" for it. (E.g. if symbol2 is "int" variable, I of course can create foo.c with "int * const symbol1 = &symbol2", but this won't match symbol1 convention from main.o, which expects symbol1 to be "int", not "int

2. Even with function this gives some overhead (one additional call;
AFAIK, wrapper function won't be inlined in this case).


On 06.10.16 15:58, Nick Clifton wrote:
Hi Sasha,

Suppose I have:
- compiled object file "main.o" with unresolved symbol "symbol1";
- build shared library "" with exported symbol "symbol2".

Is there way to somehow link program "main" from "main.o", telling it to
use "symbol2" from "" as "symbol1"?
Why not create a foo.c file that defines symbol1 and then passes any
reference on to symbol2 ?


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]