IDL 7.0.4 was recently released, providing full 64-bit support for Mac OS X, and some users who have upgraded have asked how this impacts GPULib, as using the library when running IDL in 64-bit mode doesn't work.
Currently, in order to build 64-bit code using GCC on OS X, one needs to set an additional flag, depending on the architecture targeted. We don't do this at the moment for GPULib, so it defaults to building the more compatible 32-bit libraries. Full details at
Apple goes so far as to say, "You should transition your application to a 64-bit executable format only when the 64-bit environment offers a compelling advantage for your specific application." We haven't switched to using 64-bit libraries with GPULib on Mac OS X, since thus far there hasn't been a need. If you do need the extra address space using GPULib, please let us know! Otherwise, you can add the "-32" flag to IDL 7.0.4 and run IDL in 32-bit mode, which will be compatible with the current release of GPULib.