Cannot build shared library with static member function declared in header [duplicate]

Question

Minimum reproducible example:

// dynamic.hpp
class Test {
private:
    static void update();
};

// dynamic.cpp
#include "dynamic.hpp"
#include <iostream>

void Test::update() {
    std::cout << "Hello World!" << std::endl;
}

If I try to build this using c++ -shared dynamic.cpp it fails:

/usr/bin/ld: /tmp/ccmTgJfw.o: warning: relocation against `_ZSt4cout@@GLIBCXX_3.4' in read-only section `.text'
/usr/bin/ld: /tmp/ccmTgJfw.o: relocation R_X86_64_PC32 against symbol `_ZSt4cout@@GLIBCXX_3.4' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: bad value

I do not have much experience with the linker and would like to understand what is going on here and why that does not work.

"recompile with -fPIC" - that's quite self-explanatory, nope? stackoverflow.com/a/57649548/4165552 - related — pptaszni
– pptaszni, Commented Oct 23 at 8:59
Side note: The function is defined in the cpp file, it's only declared in the header. In C++ declaration and definition are different things, and it's important to understand the difference. — john
– john, Commented Oct 23 at 9:09

Placeblock · Accepted Answer · 2025-10-23 09:08:22Z

0

Okay so the post should probably renamed to: what does -fPIC do.

After searching a little bit I found out that when compiling a shared library in this case you have to specify -fPIC to allow position independent code PIC

Originally this issue came up because I tried to link a static library to a dynamic library. It is therefore important to also build the static library using -fPIC

answered Oct 23 at 9:08

Placeblock

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