midl /align:alignment
midl /align:4 filename.idl
The /align switch is functionally the same as the MIDL /Zp option and is recognized by the MIDL compiler solely for backward compatibility with MKTYPLIB. If you are generating a new makefile, use the /Zp switch.
The alignment value corresponds to the /Zp option value used by the Microsoft C/C++ compiler.Be sure that you specify the same alignment when you invoke the C compiler as when you invoke the MIDL compiler. For more information, see your Microsoft C/C++ programming documentation.
For a discussion of the potential dangers in using nonstandard packing levels, see the /Zp help topic.
General MIDL Command-line Syntax, /Zp