Linking difference between clang and gcc - c++11

Question

I am running fedora 23 and just compiled and installed casadi 2.4.1 (however, I do not think that this is casadi specific).
I am trying to compile and run a simple test program:
#include <iostream>
#include <casadi/casadi.hpp>
using namespace casadi;
int main () {
const SX m(42);
const SX n(23);
const SX x = m + n ;
std::cout << x << std::endl;
}
It works fine with gcc:
$ g++ test.cpp -std=c++11 -I$HOME/local/include -L$HOME/local/lib -lcasadi && ./a.out
SX(65)
But using clang, I get a linker error:
$ clang++ test.cpp -std=c++11 -I$HOME/local/include -L$HOME/local/lib -lcasadi && ./a.out
/tmp/test-cde41f.o: In function `casadi::GenericMatrix<casadi::Matrix<casadi::SXElement> >::dimString() const':
test.cpp:(.text._ZNK6casadi13GenericMatrixINS_6MatrixINS_9SXElementEEEE9dimStringEv[_ZNK6casadi13GenericMatrixINS_6MatrixINS_9SXElementEEEE9dimStringEv]+0x2b): undefined reference to `casadi::Sparsity::dimString() const'
/tmp/test-cde41f.o: In function `void casadi::Sparsity::set<casadi::SXElement>(casadi::SXElement*, casadi::SXElement const*, casadi::Sparsity const&) const':
test.cpp:(.text._ZNK6casadi8Sparsity3setINS_9SXElementEEEvPT_PKS3_RKS0_[_ZNK6casadi8Sparsity3setINS_9SXElementEEEvPT_PKS3_RKS0_]+0x6f0): undefined reference to `casadi::Sparsity::dimString() const'
test.cpp:(.text._ZNK6casadi8Sparsity3setINS_9SXElementEEEvPT_PKS3_RKS0_[_ZNK6casadi8Sparsity3setINS_9SXElementEEEvPT_PKS3_RKS0_]+0x743): undefined reference to `casadi::Sparsity::dimString() const'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
I am pretty confident that the symbol is defined in the library. However, I fail to understand what clang is missing here. Is there some special c++11 ABI flag that I need to pass to the linker or something like that?

Answer 1

I would suspect version skew. Unless you do something special, clang uses some gcc stdc++ library, for which it searches. That was the case the last time I used clang for much. They may use their own std c++ library now. But if casadi was compiled with one version of gcc and you used clang which uses the std c++ library for another version of gcc, you can see linker errors like this.
You may learn something if you run clang -V to get version information. Also, gcc -v to get gcc version information, and verify that the version of gcc clang wants is the same as the version with which you are compiling.