DCMTK

ofconapp.cc: (*output) << OFendl << "Host type: " << CANONICAL_HOST_TYPE << OFendl;

So we are looking at CANONICAL_HOST_TYPE which comes from the configure machinery. CMake sets it via:

SET(CANONICAL_HOST_TYPE "${CMAKE_SYSTEM_PROCESSOR}-${CMAKE_SYSTEM_NAME}")

CMAKE_SYSTEM_PROCESSOR is documented as:

The name of the CPU CMake is building for.

On systems that support uname, this variable is set to the output of
       uname -p, on windows it is set to the value of the environment
       variable PROCESSOR_ARCHITECTURE

So I guess the 64 bit binaries were built on a 32 bit system?

Looking through the list of variables CMake defines, I don't really see anything which sounds more appropriate. And apparently CMake can't tell you if you are building 64 bit binaries or not (well, the CMake mailing list suggests looking at the size of a void pointer...).

CMake says: "Works as documented" http://public.kitware.com/Bug/print_bug_page.php?bug_id=9065

MSDN says: http://msdn.microsoft.com/en-us/library/aa384274(VS.85).aspx

commit aeb0390fb70f5390b7e253e67da6c261f3228183
Author: Uli Schlachter <dicom@offis.de>
Date:   Tue Nov 6 10:18:28 2012 +0100

    Correctly detect the processor type on 64 bit windows.
[...]
+# Windows being windows, it lies about its processor type to 32 bit binaries
+SET(SYSTEM_PROCESSOR "$ENV{PROCESSOR_ARCHITEW6432}")
+IF(NOT SYSTEM_PROCESSOR)
+  SET(SYSTEM_PROCESSOR "${CMAKE_SYSTEM_PROCESSOR}")
+ENDIF(NOT SYSTEM_PROCESSOR)
 # CMake doesn't provide a configure-style system type string
-SET(CANONICAL_HOST_TYPE "${CMAKE_SYSTEM_PROCESSOR}-${CMAKE_SYSTEM_NAME}")
+SET(CANONICAL_HOST_TYPE "${SYSTEM_PROCESSOR}-${CMAKE_SYSTEM_NAME}")
+UNSET(SYSTEM_PROCESSOR)