H2cpy stores macros with parameters for possible expansion later. If H2cpy encounters a macro with parameters and the macro definition extends over more than two or three physical lines, it may not have enough space to store all the macro details. This has no effect until H2cpy is called upon to expand that macro. If this happens, you get an error message.
If any problems occur with H2cpy not preprocessing a header file in the same way as the C compiler, this can be overcome by using the C compiler to just preprocess the header file and then use the preprocessed file as input to H2cpy.
Unlike COBOL, the C-language data types are not readily portable between environments. For this reason, H2cpy may need to be run more than once if you need to interface to the same library on different machines or operating systems.