HP aC++/HP C A.06.28 Programmer's Guide Integrity servers (769150-001, March 2014)

HP aC++ predefines the following predicates:
• #assert system(unix)
• #assert model(lp64) // when +DA2.0W is used
• #assert model(ilp32) // default
• #assert endian(big)
Example:
int main()
{
#assert dimensions(three) // Set predicate and token to true.
#if #dimensions(two)
#error "May not compile in 2 dimensions"
#endif
#if #dimensions(three)
int x, y, z;
#endif
#unassert dimensions // Set predicate and all tokens to false.
}
Conditional Compilation (#if, #ifdef, .. #endif)
Conditional compilation directives allow you to delimit portions of code that are compiled only if
a condition is true.
Syntax
conditional-directive ::=
#if constant-expression newline
#ifdef identifier newline [group]
#ifndef identifier newline [group]
#else newline [group]
#elif constant-expression newline [group]
#endif
Here, constant-expression may also contain the defined operator:
defined identifier
defined (identifier)
The constant-expression is like other C++ integral constant expressions except that all
arithmetic is carried out in long int precision. Also, the expressions cannot use the sizeof
operator, a cast, an enumeration constant, or a const object.
Description
You can use #if, #ifdef, or #ifndef to mark the beginning of the block of code that will only
be compiled conditionally. An #else directive optionally sets aside an alternative group of
statements. You mark the end of the block using an #endif directive.
The following #if directive illustrates the structure of conditional compilation:
#if constant-expression
...
(Code that compiles if the expression evaluates to a nonzero value.)
...
#else
...
(Code that compiles if the expression evaluates to zero.)
126 Preprocessing Directives