Static link libpng into a shared library

Question

I've reduced the problem to this minimal test.c:

#include "png.h"

int function() {
    printf("%ld", (long)png_create_read_struct);
}

Compiling with

gcc -shared -fPIC test.c -o test.so -lm -l:libpng16.a

gives the error

/usr/bin/ld: /usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/libpng16.a(pngread.o): relocation R_X86_64_PC32 against symbol `png_sRGB_table' can not be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Bad value

Now every answer I've found to this error boils down to "do what it says and recompile with -fPIC", but as you can see I'm already doing that. So what gives?

(Output above is from Ubuntu 17.10 with libpng16. Ubuntu 16.04 with libpng12 results in similar error.)

Answer 1

Compiling libpng with -fPIC

user@user_pc:~/Documents$ mkdir libpng
user@user_pc:~/Documents$ cd libpng
user@user_pc:~/Documents/libpng$ wget https://download.sourceforge.net/libpng/libpng-1.6.37.tar.gz
user@user_pc:~/Documents/libpng$ tar xvfz libpng-1.6.37.tar.gz
user@user_pc:~/Documents/libpng$ cd libpng-1.6.37
user@user_pc:~/Documents/libpng/libpng-1.6.37$./configure --prefix=/home/user/Documents/libpng --with-pic=yes
user@user_pc:~/Documents/libpng/libpng-1.6.37$ sudo make

Your binaries are in ~/Documents/libpng/libpng-1.6.37/lib, most interesting one is libpng.a which was now compiled with -fPIC.

It also solves problem when compiling blender on Linux as a Python module:

/usr/bin/ld.gold: error: /usr/lib/x86_64-linux-gnu/libpng.a(pngerror.o): requires dynamic R_X86_64_PC32 reloc against 'stderr' which may overflow at runtime; recompile with -fPIC
collect2: error: ld returned 1 exit status