What does the -fPIC compilation flag does?

Question

What the -fpic flag does? I want to install a library (OpenSFM) and it is stated that it will need the Ceres Solver built and installed with the -fPIC compilation flag.

The problem is I already installed the Ceres Solver without the -fPIC flag and other library already depended on it. How can I solve this?

-fPIC makes Position Independent Code for shared libraries. Alternative to shared libraries is to use static linkage — Severin Pappadeux, Aug 29 '16 at 05:12
This has nothing to do with CMake. `-fPIC` is no CMake flag, but a compiler one. — Torbjörn, Aug 29 '16 at 05:12

score 5 · Accepted Answer · edited May 23 '17 at 12:08

5

A good explaination for -fPIC can be found here.

I think the main question here is whether if you can still go ahead and install OpenSfM without rebuilding Ceres Solver. As far as I know, you can't.

The most straightforward thing you can do is rebuild Ceres Solver and reinstall the PIC version.

cmake .. -DCMAKE_C_FLAGS=fPIC \
   -DCMAKE_CXX_FLAGS=-fPIC \ 
   -DSOMEOTHERARGUMENTSTHATYOUMIGHTHAVE

Let us know how it worked out for you. :)

edited May 23 '17 at 12:08

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answered Aug 29 '16 at 05:43

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If I uninstall the Ceres Solver, and then reinstall it, can it affect the other library that depends on it (in this case, it is OpenCV)? – Hafiz Hilman Mohammad Sofian Aug 29 '16 at 06:05
Libraries compiled with -fPIC should still be compatible. – bot1131357 Aug 29 '16 at 11:00
I had the same issue while installing eiskaltdcpp from the github source. The problem still remains after setting these flags in cmake command. – Gautam Sreekumar Mar 17 '18 at 11:12

What does the -fPIC compilation flag does?

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