HP aC++/HP C Programmer's Guide (B3901-90036; A.06.26; September 2011)

Syntax
error-directive ::=
#error [preprocessor tokens]
Example
// This directive will produce the diagnostic
// message "FLAG not defined!".
#ifndef FLAG
#error "FLAG not defined!"
#endif
// This directive will produce the diagnostic
// message "TABLE_SIZE must be a multiple of 256!".
#if TABLE_SIZE % 256 != 0
#error "TABLE_SIZE must be a multiple of 256!"
#endif
Warning Directive
The #warning directive causes a diagnostic message, along with any included token
arguments, to be produced by HP aC++.
Syntax
warning-directive ::=
#warning [preprocessor tokens]
Trigraph Sequences
The C++ source code character set is a superset of the ISO 646-1983 Invariant Code
Set. To enable you to use only the reduced set, you can use trigraph sequences to
represent those characters not in the reduced set.
A trigraph sequence is a set of three characters that is replaced by a corresponding
single character. The preprocessor replaces all trigraph sequences with the corresponding
character. The list below gives the complete list of trigraph sequences and their
replacement characters. The following are all the trigraph sequences and their respective
replacement characters:
• ??= is replaced by #
• ??/ is replaced by \
• ??’ is replaced by ^
• ??( is replaced by [
• ??) is replaced by ]
• ??! is replaced by |
Overview of the Preprocessor 161