To link gcc statically into a shared library, based on the answer in this question, the remaining problem is how to let the linker use the PIC version of libc.a instead of the non-PIC version. The problem is the same as that answer:
g++ -fPIC -Wall -O0 -fexceptions -g -c main.cpp -o main.o
ld -shared -static -o test.so main.o -lc
ld: //usr/lib/x86_64-linux-gnu/libc.a(malloc.o): relocation R_X86_64_TPOFF32 against `tcache' can not be used when making a shared object; recompile with -fPIC
This is what I'v tried:
sudo apt-get install libc-pic //then libc6-pic get installed successfully
ld -shared -static -o test.so main.o -lc //same as above, same error
ld -shared -static -o test.so main.o -lc-pic //not working: cannot find -lc-pic
ld -shared -static -o test.so main.o -lc6-pic //not working: cannot find -lc6-pic
Looking at the list of files in the package there is a libc_pic.a so the correct option seems to be -lc_pic.