error linking GMP library - c++

Question

I have the following CMakeList.txt
cmake_minimum_required(VERSION 2.8)
set(CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}")
find_package(GMP REQUIRED)
add_executable(Turrial main.cpp)
with the following simple source file main.cpp
#include <iostream>
#include <gmp.h>
#include <cstdio>
using namespace std;
int main(){
mpz_t a,b;
mpz_init_set_str(a,"45",10);
mpz_init_set_str(b,"12",10);
mpz_add(a,a,b);
cout <<mpz_get_str(NULL,10,a)<<endl;
}
I have included a FindGMP.cmake file that i found online :
set(GMP_PREFIX "" CACHE PATH "path ")
find_path(GMP_INCLUDE_DIR gmp.h gmpxx.h
PATHS ${GMP_PREFIX}/include /usr/include /usr/local/include )
find_library(GMP_LIBRARY NAMES gmp libgmp
PATHS ${GMP_PREFIX}/lib /usr/lib /usr/local/lib)
if(GMP_INCLUDE_DIR AND GMP_LIBRARY)
get_filename_component(GMP_LIBRARY_DIR ${GMP_LIBRARY} PATH)
set(GMP_FOUND TRUE)
endif()
if(GMP_FOUND)
if(NOT GMP_FIND_QUIETLY)
MESSAGE(STATUS "Found GMP: ${GMP_LIBRARY}")
endif()
elseif(GMP_FOUND)
if(GMP_FIND_REQUIRED)
message(FATAL_ERROR "Could not find GMP")
endif()
endif(
when I run cmake I have the following output:
moyle#localhost:~/Desktop/gmptri$ cmake .
-- Found GMP: /usr/local/lib/libgmp.so
-- Configuring done
-- Generating done
-- Build files have been written to: /home/moyle/Desktop/gmptri
Then I run make and i get the following errors :
(precise)moyle#localhost:~/Desktop/gmptri$ make VERBOSE=1
/usr/bin/cmake -H/home/moyle/Desktop/gmptri -B/home/moyle/Desktop/gmptri --check-build-system CMakeFiles/Makefile.cmake 0
/usr/bin/cmake -E cmake_progress_start /home/moyle/Desktop/gmptri/CMakeFiles /home/moyle/Desktop/gmptri/CMakeFiles/progress.marks
make -f CMakeFiles/Makefile2 all
make[1]: Entering directory `/home/moyle/Desktop/gmptri'
make -f CMakeFiles/Turrial.dir/build.make CMakeFiles/Turrial.dir/depend
make[2]: Entering directory `/home/moyle/Desktop/gmptri'
cd /home/moyle/Desktop/gmptri && /usr/bin/cmake -E cmake_depends "Unix Makefiles" /home/moyle/Desktop/gmptri /home/moyle/Desktop/gmptri /home/moyle/Desktop/gmptri /home/moyle/Desktop/gmptri /home/moyle/Desktop/gmptri/CMakeFiles/Turrial.dir/DependInfo.cmake --color=
make[2]: Leaving directory `/home/moyle/Desktop/gmptri'
make -f CMakeFiles/Turrial.dir/build.make CMakeFiles/Turrial.dir/build
make[2]: Entering directory `/home/moyle/Desktop/gmptri'
Linking CXX executable Turrial
/usr/bin/cmake -E cmake_link_script CMakeFiles/Turrial.dir/link.txt --verbose=1
/usr/bin/c++ CMakeFiles/Turrial.dir/main.cpp.o -o Turrial -rdynamic
CMakeFiles/Turrial.dir/main.cpp.o: In function `main':
main.cpp:(.text+0x1a): undefined reference to `__gmpz_init_set_str'
main.cpp:(.text+0x30): undefined reference to `__gmpz_init_set_str'
main.cpp:(.text+0x47): undefined reference to `__gmpz_add'
collect2: ld returned 1 exit status
make[2]: *** [Turrial] Error 1
make[2]: Leaving directory `/home/moyle/Desktop/gmptri'
make[1]: *** [CMakeFiles/Turrial.dir/all] Error 2
make[1]: Leaving directory `/home/moyle/Desktop/gmptri'
make: *** [all] Error 2
can anyone help me?

Answer 1

You forget to link libraries with your executable.
find_package(GMP REQUIRED)
add_executable(Turrial main.cpp)
target_link_libraries(Turrial gmp libgmp)