HP C/iX Reference Manual (31506-90011)

Chapter 8 129
Compiling and Running HP C/iX Programs
Special Preprocessor Considerations
Special Preprocessor Considerations
The HP C/iX compiler first executes a preprocessing phase during which all preprocessor
directives (lines beginning with #) are interpreted and acted upon. See chapter 7 for
detailed information about preprocessing. This section describes features unique to the
preprocessing phase on MPE/iX systems.
Preprocessor Output File
During the preprocessing phase, an output file is created for use by the compiler. Although
the file is created with a record size and file limit that is sufficiently large for most
applications, it is possible for a source program to expand beyond the default file limit and
record size. You can use two HP C/iX compiler options, +F and +C, to overcome this
problem.
Typically, the file limit may be exceeded if you compile a very large source file or if you use
many #include directives. The compiler issues an error message indicating that the file
limit of the preprocessor output file was exceeded. To resolve this error, you must
recompile the source file using the +F compiler option to specify a larger file limit. Any
unused file space is returned when the output file is closed so you should specify a
sufficiently large file limit.
A source file might have a line that expands beyond the default record size if it contains a
large macro, a number of macros, macros that include other macros, or any combination of
these conditions. This problem is more difficult to detect because many lines can exceed
the default size without causing an error. It is only when a token, such as an identifier, is
split across two records in the output file that an error occurs. The error occurs on the line
that contains the expanded macro. To resolve this type of error, recompile using the +C
option to specify a larger record size, or reduce the size of the macro. The default record
size is 512 bytes.
Predefined Macros
The preprocessor on MPE/iX has one predefined macro, mpexl, to aid the identification and
isolation of system dependent code. This macro behaves as if the preprocessor directive
#define mpexl 1 is included at the top of the file. The mpexl macro is typically used with
the #ifdef statement.
Example
#ifdef mpexl
MPE/iX specific code ...
#endif