How can I test a Windows DLL file to determine if it is 32 bit or 64 bit?

Question

I'd like to write a test script or program that asserts that all DLL files in a given directory are of a particular build type.

I would use this as a sanity check at the end of a build process on an SDK to make sure that the 64-bit version hasn't somehow got some 32-bit DLL files in it and vice versa.

Is there an easy way to look at a DLL file and determine its type?

The solution should work on both xp32 and xp64.

Answer 1

A crude way would be to call dumpbin with the headers option from the Visual Studio tools on each DLL and look for the appropriate output:

dumpbin /headers my32bit.dll

PE signature found

File Type: DLL

FILE HEADER VALUES
             14C machine (x86)
               1 number of sections
        45499E0A time date stamp Thu Nov 02 03:28:10 2006
               0 file pointer to symbol table
               0 number of symbols
              E0 size of optional header
            2102 characteristics
                   Executable
                   32 bit word machine
                   DLL

OPTIONAL HEADER VALUES
             10B magic # (PE32)

You can see a couple clues in that output that it is a 32 bit DLL, including the 14C value that Paul mentions. Should be easy to look for in a script.