Travis-CI fails on symbol lookup error, works fine elsewhere

问题

I have a library (technically a Ruby extension) called NMatrix which is written in C and C++. It uses C++ templates to manage different types, e.g., Rational128 versus Rational64. It also has RubyObject and Complex64 and Complex128. I force these template versions to be built by creating some inside an object file -- in a function that is called from the library entry point.

It works just fine in GCC 4.7, but when I compile on Travis-CI, it encounters an undefined symbol error at run-time:

exposes cblas rot /home/travis/.rvm/rubies/ruby-2.0.0-p247/bin/ruby: symbol lookup error: /home/travis/build/SciRuby/nmatrix/lib/nmatrix.so: undefined symbol: _ZN2nm7ComplexIfEC1ERKNS_10RubyObjectE

The undefined symbol is nm::Complex::Complex(nm::RubyObject const&), which is explicitly defined and instantiated (see below).

Here's a pared down version of data.cpp:

#include "data.h"

void nm_init_data() { // called from library entry point
  // These force the compiler to build these versions of the typedef'd templates.
  // I think this is a gross way to do it, but can't find a better idea.
  nm::RubyObject obj(INT2FIX(1));
  nm::Rational32 x(obj);
  nm::Rational64 y(obj);
  nm::Rational128 z(obj);
  nm::Complex64 a(obj);    // Clear instantiation of the undefined symbol
  nm::Complex128 b(obj);
}

and data.h like so:

#include "nmatrix.h"

#include "complex.h" // classes are all declared in headers
#include "rational.h"
#include "ruby_object.h"

void nm_init_data();

nmatrix.cpp is where the library entry point is declared. The relevant parts look like this:

void Init_nmatrix() {
  // declarations of Ruby-exposed functions here, e.g., 
  rb_define_method(cNMatrix, "initialize", (METHOD)nmatrix_constructor, -1);

  nm_init_data();
}

So what am I doing wrong? Why does this work on GCC 4.7.1 (all specs pass), but not 4.6.3? Is it a bug? (If it's a bug, is there a work-around?)

If you're curious, the full versions of the relevant files are here.

来源：https://stackoverflow.com/questions/19055501/travis-ci-fails-on-symbol-lookup-error-works-fine-elsewhere

标签

c++

gcc

travis-ci

gcc4.6