#214 multiple contexts with C++

[IOhannes m zmölnig]

i'm using glew-1.9.0.

when trying to add multiple window support to my C++ project, i
noticed that the linker would bail out, claiming that a lot of
__glewX... (e.g. __glewXCushionSGI) things have beem multiply defined.

• those "things" are function-pointers (that is: named variables
  pointing to a function)
• my project consists of multiple C++ files
• for various reasons i'm including the file "glxew.h" in multiple
  C++-files
• when compiling with GLEW_MX, the macro GLXEW_FUN_EXPORT expands to
  nothing, whereas when compiling without multicontext support, it
  expands to GLEW_FUN_EXPORT which expands to "extern ... "
• therefore, when using GLEW_MX, i get multiple definitions of those
  variables.

this only happens in C++, C is fine.

see attached example. (edit the Makefile to compile with glew vs
glew-mx; rename the .cpp files to .c to verify that it works with C)

changing the definition of GLXEW_FUN_EXPORT to GLEW_FUN_EXPORT
regardless of the GLEW_MX state, seems to fix the problem for me.

[Nigel Stewart]

Thanks for the reproducer, very helpful.

For Ubuntu 12.04, it works fine for me in both modes.
(with libglew1.6-dev installed)

$ make
g++ -I. -DGLEW_MX -I/usr/include/GL     -c -o main.o main.cpp
g++ -I. -DGLEW_MX -I/usr/include/GL     -c -o render.o render.cpp
g++ -o glewtest main.o render.o -lGLEWmx -lGLU -lGL    -L/usr/X11R6/lib -lXxf86vm -lX11

However, using the tarballs I can confirm:

1.7.0 - OK
1.8.0 - broken
1.9.0 - broken
1.10.0 - OK (in progress)

Would you mind trying this snapshot to see if this problem is resolved
for you too?

http://sourceforge.net/projects/glew/files/glew/snapshots/glew-20130318.tgz/download

• Nigel

[IOhannes m zmölnig]

sorry for not being able to reply earlier. i now tried the 0.10.0 release, and indeed it seems that the problem is gone. thanks for fixing!

[Nigel Stewart]

Fixed in GLEW 1.10.0
Closing.
Thanks for the report.