How to make/build project against one version of a library but its dependencies against a different version of that library?

Question

I have workspace structure as shown below. It involves PROJ for project, TPL for third party library and DEP-PROJ for dependency project (and ws for workspace). I have also specified their dependencies inside brackets, next to them.

ws   
├── opencv34
│   ├── opencv
│   └── opencv_contrib
├── opencv44
|   ├── opencv
|   └── opencv_contrib
├── DEP-PROJ (opencv 3.4)
└── PROJ (DEP-PROJ, opencv 4.4)
    └── TPL (opencv 4.4) 

I have built both versions of opencv with cmake .. and make -j6 commands. But did not run make install.

Next, DEP-PROJ has following lines in its CMakeLists.txt (notice OPENCV3_DIR):

set(OpenCV_DIR $ENV{OPENCV3_DIR})
find_package(OpenCV 3.4 REQUIRED) 

Before doing cmake in DEP-PROJ/build directory, I run export OPENCV3_DIR=/ws/opencv34/opencv/build, so that cmake succeeds.

Next, PROJ has following lines in its CMakeLists.txt (notice OPENCV4_DIR):

set(OpenCV_DIR $ENV{OPENCV4_DIR})
find_package(OpenCV 4.4 REQUIRED)

Next, before doing cmake in PROJ/build directory, I run export OPENCV4_DIR=/ws/opencv34/opencv/build, so that cmake succeeds.

Before doing cmake in PROJ/build directory, I run export OPENCV4_DIR=/ws/opencv44/opencv/build, so that cmake succeeds.

This cause cmake to succeed, but make fails with error:

fatal error: opencv/cv.h: No such file or directory

It seems that doing make inside PROJ rebuilds DEP-PROJ. However, CMakeLists.txt of PROJ sets OpenCV_DIR to opencv44 directory. This makes DEP-PROJ build fail giving above error.

To avoid this, I run make install inside /ws/opencv34/opencv/build. This lets DEP-PROJ find opencv 3.4 from /usr directory and PROJ references opencv 4.4 from /ws/opencv44/opencv/build directory leading to successfully building PROJ.

However, I feel its a bit hacky way to resolve this (doing make install in opencv 3.4 and not doing it in opencv 4.4). What is correct way to do this? How can I avoid rebuilding DEP-PROJ while building PROJ? or build it against /ws/opencv34/opencv/build (instead of opencv in /usr) along with building PROJ against /ws/opencv44/opencv/build?

PS: I am noob in cmake.

Answer 1

TL;DR: mixing multiple versions of a single library in the same process on UNIX doesn't work, just give up!

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You appear to be building for UNIX.

Unlike on Windows, a UNIX shared library is not self-contained -- it is subject to symbol interposition and symbol collisions.

Also, OpenCV versions 3.4 and 4.4 define the same symbols, and are not ABI-compatible.

Taken together the two statements above mean that IF you manage to link your project dynamically with versions 3.4 and 4.4 of OpenCV, you are almost guaranteed to have inexplicable crashes, memory corruption, and more.

(If you try to link your project with archive versions instead, you will most likely fail with multiple symbol definition instead.)