How to recompile ntl and gmp libraries with "-fPIC" flag & make HELib as a shared library & undefined reference to func(std::ostream&) error

a C++ code built into a shared library for HELib is using NTL and GMP static library. But it gets following error:

/usr/bin/ld: /usr/local/lib/libntl.a(FFT.o): relocation R_X86_64_32 against `.rodata.str1.8' can not be used when making a shared object; recompile with -fPIC
/usr/local/lib/libntl.a: error adding symbols: Bad value collect2: error: ld returned 1 exit status

It was suggested int the post Click here

to recompile NTL and GMP with "-fPIC " flags. I'am not able to find how I should do that.

Edit:

I'm able to build the shared library now after : recompiling GMP and NTL by: ./configure --enable-shared
for gmp and ./configure SHARED=on

After make Install of HELib. I get error when I run the example codes. The link to the Makefile : click to see makefile

Error:

g++ -g -O2 -std=c++11 -pthread -DFHE_THREADS -DFHE_BOOT_THREADS -DFHE_DCRT_THREADS -o Test_General_x Test_General.cpp -L/usr/local/lib -lntl -lgmp -lm -lfhe /usr/local/lib/libfhe.so: undefined reference to write_raw_int(std::ostream&, long, long)' /usr/local/lib/libfhe.so: undefined reference toread_raw_ZZ(std::istream&, NTL::ZZ&)' /usr/local/lib/libfhe.so: undefined reference to void write_raw_vector<long>(std::ostream&, std::vector<long, std::allocator<long> > const&)' /usr/local/lib/libfhe.so: undefined reference towriteEyeCatcher(std::ostream&, char const*)' /usr/local/lib/libfhe.so: undefined reference to write_raw_xdouble(std::ostream&, NTL::xdouble)' /usr/local/lib/libfhe.so: undefined reference toread_ntl_vec_long(std::istream&, NTL::Vec&)' /usr/local/lib/libfhe.so: undefined reference to void read_raw_vector<long>(std::istream&, std::vector<long, std::allocator<long> >&)' /usr/local/lib/libfhe.so: undefined reference toreadEyeCatcher(std::istream&, char const*)' /usr/local/lib/libfhe.so: undefined reference to read_raw_int(std::istream&, long)' /usr/local/lib/libfhe.so: undefined reference toread_raw_xdouble(std::istream&)' /usr/local/lib/libfhe.so: undefined reference to write_raw_ZZ(std::ostream&, NTL::ZZ const&)' /usr/local/lib/libfhe.so: undefined reference towrite_ntl_vec_long(std::ostream&, NTL::Vec const&, long)' collect2: error: ld returned 1 exit status Makefile:179: recipe for target 'Test_General_x' failed make: *** [Test_General_x] Error 1

Marc Glisse provided the answer for the first two parts of the question.For the third part "Undefined Reference error" the answer is I'd not compiled and linked a x.cpp containing the functions that caused the undefined reference into my shared library. hence check : nm -CD /usr/local/lib/libfhe.so to see if these functions are listed with a linking address or not. If not then check which code provides this functionality. Link that code to the shared library.