[SOLVED] Undefined reference to `FastPForLib:..' while linking FastPForlib

Issue

Any suggestion regarding the following query would be appreciated. I have tried everything and am still struck with this error. The library (FastPFor) works fine with the visual studio solution; the issue arises when I try to use it with my project containing the file (src/example.cpp).

I am trying to link the static library (lib/FastPFor/libFastPFOR.a) to my example.cpp. I have copied the header files in the (include/FastPFor/*h) while I obtained FastPForlib.a by running the CMake command followed by make, on Ubuntu run via WSL.

Following is my dependency-tree

example (proj)
include
------------>FastPFor
--------------------->*h
lib
------------>FastPFor
--------------------->liblibFastPFor.a
src
------------>example.src
Makefile

Following is my makefile:

.SUFFIXES:
#
.SUFFIXES: .cpp .o .c .h
LDFLAGS = -Llib/FastPFor -llibFastPFOR
# replace the CXX variable with a path to a C++11 compatible compiler.
# to build an aligned version, add -DUSE_ALIGNED=1
ifeq ($(INTEL), 1)
# if you wish to use the Intel compiler, please do "make INTEL=1".
    CXX ?= /opt/intel/bin/icpc
    CC ?= /opt/intel/bin/icpc
ifeq ($(DEBUG),1)
    CXXFLAGS = -fpic -std=c++11 -O3 -Wall -ansi -xAVX -DDEBUG=1 -D_GLIBCXX_DEBUG -ggdb 
    CCFLAGS = -fpic -std=c99 -O3 -Wall  -ansi -xAVX -DDEBUG=1 -D_GLIBCXX_DEBUG -ggdb 
else
    CXXFLAGS = -fpic -std=c++11 -O2 -Wall  -ansi -xAVX -DNDEBUG=1  -ggdb 
    CCFLAGS = -fpic -std=c99 -O2 -Wall   -ansi -xAVX -DNDEBUG=1  -ggdb 
endif # debug
else #intel
    CXX ?= g++-4.7
ifeq ($(DEBUG),1)
    CXXFLAGS = -fpic -mavx -std=c++11  -Weffc++ -pedantic -ggdb -DDEBUG=1 -D_GLIBCXX_DEBUG -Wall  -Wextra -Wextra -Wsign-compare  -Wwrite-strings -Wpointer-arith -Winit-self  -Wno-sign-conversion
    CCFLAGS = -fpic -mavx -std=c99  -pedantic -ggdb -DDEBUG=1 -D_GLIBCXX_DEBUG -Wall  -Wextra -Wsign-compare -Wwrite-strings -Wpointer-arith -Winit-self  -Wno-sign-conversion 
else
    CXXFLAGS = -fpic -mavx -std=c++11  -Weffc++ -pedantic -O3 -Wall  -Wextra -Wsign-compare  -Wwrite-strings -Wpointer-arith -Winit-self  -Wno-sign-conversion 
    CCFLAGS = -fpic -mavx -std=c99 -pedantic -O3 -Wall -Wextra -Wsign-compare -Wwrite-strings -Wpointer-arith -Winit-self -Wno-sign-conversion 
endif #debug
endif #intel


HEADERS= $(shell ls include/FastPFor/*.h)

all: example


example: $(HEADERS) src/example.cpp
    $(CXX) $(CXXFLAGS) -o example $(LDFLAGS) src/example.cpp 

clean:
    rm -f *.o example

astyle:
    astyle --options=astyle.conf --recursive "*.cpp" "*.h"

.PHONY: all clean astyle

Running make produced bunch of errors, all related to undefined reference to FastPFOR. It looks something like following:

/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x781): undefined reference to `__fastunpack11(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x791): undefined reference to `__fastunpack10(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x7a1): undefined reference to `__fastunpack9(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x7b1): undefined reference to `__fastunpack4(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x7c1): undefined reference to `__fastunpack3(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x7d1): undefined reference to `__fastunpack64(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x7e1): undefined reference to `__fastunpack8(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x7f1): undefined reference to `__fastunpack7(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x801): undefined reference to `__fastunpack6(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x811): undefined reference to `__fastunpack5(unsigned int const*, unsigned long*)'
/usr/bin/ld: example.cpp:(.text._ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm[_ZN11FastPForLib12FastPForImplILj8EmE13__decodeArrayEPKjRmPmm]+0x87c): undefined reference to `__fastunpack2(unsigned int const*, unsigned long*)'
collect2: error: ld returned 1 exit status
make: *** [Makefile:36: example] Error 1

Thank you in advance.

Solution

First please always include the command (in this case, link line) that make printed out before you got your errors, when asking questions.

The problem is the order in which you have things on the link line. -llibFastPFOR is not an option per se, it tells the linker to look at that file and include any symbols that are needed but are currently undefined. But since you put this first on your link line, before example.cpp, there are no symbols (other than main) that are needed yet.

You have to put the source (and object) files first on the link line, before the libraries. So change your linker command to:

$(CXX) $(CXXFLAGS) -o example src/example.cpp $(LDFLAGS)

This is not a very standard/well-behaved makefile in a lot of ways, but this change should solve your immediate problem.

Answered By - MadScientist

Answer Checked By - Clifford M. (WPSolving Volunteer)