Two library of different versions in an application

Question

Consider a scenario where there are two shared library of different version.Consider A.1.so linked to B.so and A.2.so linked to C.so. Now both B.so and C.so are linked to d.exe . When B.so wants to invoke function in A.1.so, it ends up calling function in A.2.so .Because of this , it gives us undefined behaviour.

Now I want my B.so invoke only A.1.so.I can only modify A.1.so and B.so , nothing else. Using dlopen() is one of the option, but for using dlopen(), I have to make heavy changes in B.so. There are many solutions given earlier in Stack Overflow, but nothing seems to work. Kindly note that I can make code changes in A.1.so and B.so only.

Is there any other solution to this problem other than dlopen(). I have mentioned some of the links below.

(you'll obviously have the rename the symbols exposed by the library to match) — Sander De Dycker, Jul 09 '19 at 08:14
@SanderDeDycker i tried , it did not work , even if the library name is different, the function name inside the library is same — Abhishek Garg, Jul 09 '19 at 08:58
@SanderDeDycker I tried--default-symver, it did not work, maybe i have made some mistake , but it did not work. — Abhishek Garg, Jul 09 '19 at 09:00
@SanderDeDycker If I add my_ in front of all symbols , I have to make changes in A.1.so and B.so , and that changes will be really huge.This change is no better than dlopen().I need something which can make this thing work with minimal changes. — Abhishek Garg, Jul 09 '19 at 10:56
Do you also want for C.so to invoke only from A.2.so ? Or are you ok with A1.so to hide A2.so implementation ? — MichaelCMS, Jul 09 '19 at 14:37
@MichaelCMS actually i don't want A1.so to hide A2.so . Anyway for knowledge sake lets assume that i want A1.so to hide A2.so.One possiblle way is using LD_PRELOAD. Is there any other way?? — Abhishek Garg, Jul 10 '19 at 03:10
@AbhishekGarg LD_PRELOAD is the correct way for hiding.For what you are asking I think that what you are seeking to do is to compile the B.so with static linkage to A1.so. You cannot achieve what you want while having both using dynamic linkage. However if you static link B.so to A1.so the calls should work. — MichaelCMS, Jul 11 '19 at 11:18
@SanderDeDycker When u say prepend my_ to all external symbols, did u mean renaming all functions in codebase — Abhishek Garg, Jul 17 '19 at 13:37

score 0 · Answer 1 · edited Jul 17 '19 at 20:00

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can you wrap all code in A1.cpp in namespace A1 and add a using namespace A1 to B.cpp? By A1.cpp an B.cpp I mean all the relevant translation units for A1.so and B.so.

edited Jul 17 '19 at 20:00

Jonathan Leffler

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answered Jul 16 '19 at 18:11

nriedlin

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Two library of different versions in an application

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