title: linking error: "undefined reference to `pthread_atfork'" in Armadillo library
body: <p>recently I updated my armadillo to version 5.200.1, but when i tried to compile my code using</p>
  
  <pre><code>g++ -std=c++11 -m64 -O3 -Wall -I. -I/opt/OpenBLAS/include -fopenmp -o code.cpp.o -c code.cpp
  g++ -std=c++11 -m64 -O3 -Wall -I. -I/opt/OpenBLAS/include -fopenmp -o main.cpp.o -c main.cpp
  g++ -std=c++11 -m64 -O3 -o code.cpp.o main.cpp.o -lgomp -L/opt/OpenBLAS/lib -lopenblas -larmadillo
  </code></pre>
  
  <p>I got error message in the final linking step</p>
  
  <blockquote>
    <p>/usr/lib/gcc/x86_64-linux-gnu/4.9/../../../../lib/libarmadillo.so:
    undefined reference to `pthread_atfork'</p>
    
    <p>collect2: error: ld returned 1 exit status </p>
    
    <p>make: *** [a.out] Error 1</p>
  </blockquote>
  
  <p>This error appears in my machine with Ubuntu 14.04LTS + gcc 4.9.2.
  The Armadillo itself is linked with OpenBLAS 0.2.14 (I followed the procedure provided by Armadillo in installation)</p>
  
  <p>such error doesn't occur in my macosx laptop (the same library). It means something problems with my ubuntu machine. I tried to re-install the Armadillo 4.650.2 (this version worked before), but the same error kept appearing (now older doesn't work like before). The only thing that i did before updating those libraries were "apt-self update" and "apt-self upgrade" of my ubuntu machine</p>
  
  <p>is there any suggestion to fix this problem?</p>