使用 NTL 库的编译器错误

Question

I'm trying to use NTL library, but I always get compiler errors about undefined symbols.

Example (taken from the NTL documentation):

#include <NTL/ZZ.h>

NTL_CLIENT

int main()
{
   ZZ a, b, c; 

   cin >> a; 
   cin >> b; 
   c = (a+1)*(b+1);
   cout << c << "\n";
}

Result:

$ g++ -lntl simple.cpp
/tmp/ccGwxURb.o: In function `main':
simple.cpp:(.text+0x3a): undefined reference to `NTL::operator>>(std::basic_istream<char, std::char_traits<char> >&, NTL::ZZ&)'
simple.cpp:(.text+0x4b): undefined reference to `NTL::operator>>(std::basic_istream<char, std::char_traits<char> >&, NTL::ZZ&)'
simple.cpp:(.text+0xda): undefined reference to `NTL::operator<<(std::basic_ostream<char, std::char_traits<char> >&, NTL::ZZ const&)'
/tmp/ccGwxURb.o: In function `NTL::ZZ::operator=(NTL::ZZ const&)':
simple.cpp:(.text._ZN3NTL2ZZaSERKS0_[NTL::ZZ::operator=(NTL::ZZ const&)]+0x22): undefined reference to `_ntl_gcopy'
/tmp/ccGwxURb.o: In function `NTL::ZZ::~ZZ()':
simple.cpp:(.text._ZN3NTL2ZZD2Ev[_ZN3NTL2ZZD5Ev]+0x14): undefined reference to `_ntl_gfree'
/tmp/ccGwxURb.o: In function `NTL::add(NTL::ZZ&, NTL::ZZ const&, long)':
simple.cpp:(.text._ZN3NTL3addERNS_2ZZERKS0_l[NTL::add(NTL::ZZ&, NTL::ZZ const&, long)]+0x2a): undefined reference to `_ntl_gsadd'
/tmp/ccGwxURb.o: In function `NTL::mul(NTL::ZZ&, NTL::ZZ const&, NTL::ZZ const&)':
simple.cpp:(.text._ZN3NTL3mulERNS_2ZZERKS0_S3_[NTL::mul(NTL::ZZ&, NTL::ZZ const&, NTL::ZZ const&)]+0x2d): undefined reference to `_ntl_gmul'
collect2: ld returned 1 exit status

The NTL headers are in /usr/include/NTL , so they should be included.

What's the problem? Am I compiling in the wrong way? If so, where can I find the right way, since it seems like there is not such a thing like "how to compile with ntl" in the documentation?

If I use using namespace NTL instead of NTL_CLIENT nothing changes:

$ ls /usr/lib | grep libntl
libntl-5.4.2.so
libntl.a
libntl.so
$ ls /usr/include | grep NTL
NTL
$ g++ -L/usr/lib -lntl -lgmp -lm simple.cpp
/tmp/ccwdQkr4.o: In function `main':
simple.cpp:(.text+0x3a): undefined reference to `NTL::operator>>(std::basic_istream<char, std::char_traits<char> >&, NTL::ZZ&)'
simple.cpp:(.text+0x4b): undefined reference to `NTL::operator>>(std::basic_istream<char, std::char_traits<char> >&, NTL::ZZ&)'
simple.cpp:(.text+0xda): undefined reference to `NTL::operator<<(std::basic_ostream<char, std::char_traits<char> >&, NTL::ZZ const&)'
/tmp/ccwdQkr4.o: In function `NTL::ZZ::operator=(NTL::ZZ const&)':
simple.cpp:(.text._ZN3NTL2ZZaSERKS0_[NTL::ZZ::operator=(NTL::ZZ const&)]+0x22): undefined reference to `_ntl_gcopy'
/tmp/ccwdQkr4.o: In function `NTL::ZZ::~ZZ()':
simple.cpp:(.text._ZN3NTL2ZZD2Ev[_ZN3NTL2ZZD5Ev]+0x14): undefined reference to `_ntl_gfree'
/tmp/ccwdQkr4.o: In function `NTL::add(NTL::ZZ&, NTL::ZZ const&, long)':
simple.cpp:(.text._ZN3NTL3addERNS_2ZZERKS0_l[NTL::add(NTL::ZZ&, NTL::ZZ const&, long)]+0x2a): undefined reference to `_ntl_gsadd'
/tmp/ccwdQkr4.o: In function `NTL::mul(NTL::ZZ&, NTL::ZZ const&, NTL::ZZ const&)':
simple.cpp:(.text._ZN3NTL3mulERNS_2ZZERKS0_S3_[NTL::mul(NTL::ZZ&, NTL::ZZ const&, NTL::ZZ const&)]+0x2d): undefined reference to `_ntl_gmul'
collect2: ld returned 1 exit status
$ cat simple.cpp
#include <NTL/ZZ.h>

using namespace NTL;

int main()
{
   ZZ a, b, c; 

   std::cin >> a; 
   std::cin >> b; 
   c = (a+1)*(b+1);
   std::cout << c << "\n";
}

Answer 1

These are not compiler errors. These are linker errors. It isn't sufficient to include the header during compilation. You also need to specify the libraries being used during linking.

I don't know about NTL so I don't know which library needs to be included but I would expect that it is mentioned somewhere in whatever documentation is available. A quick search with Google seems to indicate that you need to use -lntl (assuming the library is installed in a standard directory).

Note that traditionally C compilers process the command line from left to right, so you should add -lntl before the source file that uses the NTL library.

Answer 2

I had the same issue and after reading the NTL docs, I used the following:

g++ -g -O2 -std=c++11 -pthread -march=native foo.cpp -o foo -lntl -lgmp -lm

I think the gmp library is also required alongside with ntl.

Answer 3

I had somewhat of the same problem when I first started using the library. After having compiled the library, every time you use the library for a project, you have to go to Project > Add Existing Item (shortcut key: Ctrl + Shift + A ) and select the .lib file you produced when compiling the library.

If this doesn't work, feel free to Inbox me and I can send you detailed instructions I have documented on how to Compile the library and utilize it.

Answer 4

Hi to solve this problem you should run program by terminal for example

 g++ simple.cpp -o simple -lntl

then to show result write

./simple

Answer 5

I had a similar issue. I was using Codelite IDE on ubuntu. I solved the issue by changing the order in Setting --> Linker --> Libraries as follows:

ntl gmp

When the order is different (gmp;ntl) then I was getting the error.

So please check the order and move ntl first before gmp