-fPIC switch has stopped working?

knobby67 · 03-23-2018, 06:42 AM

Hi All,
I just upgraded to a new PC that I need to use use ubuntu 17 on ( graphics drivers )

I've went to compile some code that's always worked, it links against an external .o file ( not my file ), however I now get a liking error and am told to use -fPIC. However I use fPIC in my makefile

Code:

CC   =$(TRGT)g++ -fPIC -std=c++0x
CP   = $(TRGT)objcopy
AS   = $(TRGT)gcc -x assembler-with-cpp

the error is

Code:

iodriver_x64.o: relocation R_X86_64_32S against `.rodata' cannot be used when making a shared object; recompile with -fPIC
/usr/bin/ld: final link failed: Nonrepresentable section on output
collect2: error: ld returned 1 exit status

Is there some error with fPIC now? "gcc version 7.2.0 (Ubuntu 7.2.0-8ubuntu3.2)" Does anyone know a way I can fix this? Thanks

NevemTeve · 03-23-2018, 08:36 AM

You should find the line in the compilation-log (hopefully you do have one) which created the object module. For some reason it was compiled without -fPIC (Most likely it wasn't compiled with recent gcc/g++ as they use -fPIC by default on x86_64 platform.)

Note: usually, CC is the C-compiler, CXX is the C++-compiler.

knobby67 · 03-23-2018, 10:22 AM

So it’s the object file the needs -fPIC not my end? If so I’ll have to get onto them.
Thanks

NevemTeve · 03-23-2018, 11:59 AM

For example:

Code:

clang -o whatnot.o -c whatnot.c   # doesn't default option -fPIC
gcc   -o whatnot      whatnot.o   # defaults option -pie ==> fail

knobby67 · 03-23-2018, 12:38 PM

Sorry I didn't make myself clear. By object file I mean the one provided by the io board manufacturer? I have my code .c and compile in their .o. What I was asking is it them when they compile the .o file who need to use -fPIC. Do I need to contact them and ask them to provide the .o after they have compiled with -fPIC? Thanks

NevemTeve · 03-23-2018, 01:58 PM

The error message states that 'iodriver_x64.o' was compiled without '-fPIC'
You cannot create shared library or relocatable executable from it, but you still can create 'plain old' executable with gcc-linker-option '-no-pie'

Example:

Code:

clang -o whatnot.o    -c whatnot.c
gcc   -o whatnot -no-pie whatnot.o

knobby67 · 03-23-2018, 02:28 PM

Ahh right thanks