Difference in MIDL output beween Win32 and x64

Question

Hi,
Currently we are using the MIDL compiler to generate _i.h (header), _i.c (IID), and .tlb (type library) files.  Since we are using the universal marshaller, we don't need proxy/stub files.
1. I am assuming there is no significant difference between those files when generated in a debug vs a release build for the same platform.  Is that assumption correct?
2. Currently I don't see any significant difference between our generated headers and IID files when generated for Win32 platform vs x64 platform.  Could they be different between the two platforms?  We are sticking to automation/variant compatible
types -- just in case that affects the answer.
3. I do see what appear to be significant differences between the .tlbs generated for the Win32 vs the x64 platform.  Is that correct?
Thanks in advance.
Nick

Answer 1

Thanks for your response.
For the first question, I am aware that the C++ compiler does optimizations in a release build.  Were you trying to say that: (a) the MIDL compiler does optimizations when generating tlb files in release, or (b) the answer is obvious, there
is no difference between debug/release for these generated files?  I am guessing you meant (b), but just checking.
As for the differences between 32-bits and 64-bits for .tlb files, could you expand why they are the same?  When I did a binary/hex comparison between them for debug/release, I only saw very few changes, all around the date/time stamp section, so the
differences appeared to be insignificant.  However, when I did a binary comparison between 32-bits and 64-bits, the differences were all over the place (mostly 1-byte differences oddly enough).  I don't know enough about differences between 32-bit
and 64-bit binaries to know what that means.
I did a bit more reading into this and found the following.
https://msdn.microsoft.com/en-us/library/ms810720.aspx
As of summer 1999, (i.e. Windows 2000 Pro RCx releases), the 64b type libraries are supported by mapping 32b *.TLB files. When porting
a project using TLBs, one should build 32b TLB files in the 32b environment for the project. Then the native 64b oleaut32.dll provides an appropriate 64b mapping for the TLB files at runtime.
Then there is this from https://msdn.microsoft.com/en-us/library/windows/desktop/aa367323(v=vs.85).aspx :
win32
Directs the MIDL compiler to generate stub files, or a type library file,
for a 32-bit environment.
ia64
Directs the MIDL compiler to generate stub files, or a type libraryfile, for a Intel Architecture 64-bit (IA64) environment.