Linking with gl3n can't find reference to _Dmodule_ref

August 25, 2013
Posted by Nordlöw
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Nordlöw
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I'm starting a geometry module (fixed dimensional linear algebra) similar to Boost.Geometry.
I want these structures to have tight integration with OpenGL wrappers.
I've built and installed gl3n and thought it would be a good base to start with.

But when I try to link my sample application

#!/usr/bin/env rdmd

pragma(lib, "gl3n");

import gl3n.linalg;
import std.stdio;
import std.algorithm;

void main(string args[]) {
    writeln(vec2(2, 3).x);
    writeln(vec2(2, 3));
    writeln(cross(vec3(2, 3, 4),
                  vec3(4, 3, 2)));
    writeln(dot(vec3(2, 3, 4),
                vec3(4, 3, 2)));
    writeln(vec3(2, 3, 4));
}

I get the linking error

/home/per/opt/x86_64-unknown-linux-gnu/dmd/bin/dmd -debug -gc -unittest -D -Dd/home/per/.emacs.d/auto-builds/dmd/Debug-Boundscheck-Unittest/home/per/Work/cognia/ -w  ~/Work/cognia/geometry.d -of/home/per/.emacs.d/auto-builds/dmd/Debug-Boundscheck-Unittest/home/per/Work/cognia/geometry
/home/per/opt/x86_64-unknown-linux-gnu/dmd/bin/../lib/libgl3n.a(util.o): In function `no symbol':
gl3n/util.d:(.text+0x6): undefined reference to `_Dmodule_ref'
/home/per/opt/x86_64-unknown-linux-gnu/dmd/bin/../lib/libgl3n.a(linalg.o): In function `no symbol':
gl3n/linalg.d:(.text+0x6): undefined reference to `_Dmodule_ref'
/home/per/opt/x86_64-unknown-linux-gnu/dmd/bin/../lib/libgl3n.a(plane.o): In function `no symbol':
gl3n/plane.d:(.text+0x6): undefined reference to `_Dmodule_ref'
/home/per/opt/x86_64-unknown-linux-gnu/dmd/bin/../lib/libgl3n.a(plane.o): In function `_D4gl3n5plane13__T6PlaneTTfZ6PlaneT8opEqualsMxFNaNbNfS4gl3n5plane13__T6PlaneTTfZ6PlaneTZb':
gl3n/plane.d:(.text._D4gl3n5plane13__T6PlaneTTfZ6PlaneT8opEqualsMxFNaNbNfS4gl3n5plane13__T6PlaneTTfZ6PlaneTZb+0x51): undefined reference to `_D4gl3n6linalg16__T6VectorTfVi3Z6Vector53__T8opEqualsTxS4gl3n6linalg16__T6VectorTfVi3Z6VectorZ8opEqualsMxFNaNbNfxS4gl3n6linalg16__T6VectorTfVi3Z6VectorZb'
/home/per/opt/x86_64-unknown-linux-gnu/dmd/bin/../lib/libgl3n.a(math.o): In function `no symbol':
gl3n/math.d:(.text+0x6): undefined reference to `_Dmodule_ref'
collect2: error: ld returned 1 exit status
--- errorlevel 1

I know DMD finds the libgl3n.a because otherwise it complains about hundreds of missing symbols.
It is however strange that a single gl3n-symbol is missing.
Maybe there's a bug gl3n.

I've tried adding

extern (C) void* _Dmodule_ref = null;

the line as indicated in other threads but then again I get

/home/per/opt/x86_64-unknown-linux-gnu/dmd/bin/dmd -debug -gc -unittest -D -Dd/home/per/.emacs.d/auto-builds/dmd/Debug-Boundscheck-Unittest/home/per/Work/cognia/ -w  ~/Work/cognia/geometry.d -of/home/per/.emacs.d/auto-builds/dmd/Debug-Boundscheck-Unittest/home/per/Work/cognia/geometry
/usr/bin/ld: _Dmodule_ref: TLS definition in /home/per/.emacs.d/auto-builds/dmd/Debug-Boundscheck-Unittest/home/per/Work/cognia/geometry.o section .tbss mismatches non-TLS reference in /home/per/opt/x86_64-unknown-linux-gnu/dmd/bin/../lib/libgl3n.a(util.o)
/home/per/opt/x86_64-unknown-linux-gnu/dmd/bin/../lib/libgl3n.a: could not read symbols: Bad value
collect2: error: ld returned 1 exit status
--- errorlevel 1

I can't understand what the meaning of _Dmodule_ref even not after having read about it in other threads.
Some say it has to do with linking to C libraries but gl3n doesn't use C libraries.

The error is removed when I remove

pragma(lib, "gl3n");

along with the import and uses gl3n structures (of course)

so the symbols _Dmodule_ref is referenced from libgl3n.a

What is wrong?

Thx,
Per Nordlöw
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