HP C Programmer's Guide (92434-90009)

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148 Chapter5

Programming for Portability

Porting between HP C and Domain/C

All HP-UX and Domain computers have ANSI C compilers. Strictly standard-compliant

programs are highly portable between all these architectures.

The following Domain/C extensions are not supported on HP-UX in compatibility mode

and in most cases, are not supported in ANSI mode either:

• Reference variables.

• The following preprocessor directives: #attribute, #options, #section, #module,

#debug, #eject, #list, #nolist, and #systype.

• std_$call.

• attribute modiﬁer and options speciﬁer.

• systype predeﬁned macro.

• _BFMTCOFF predeﬁned macro.

• _ISPM68K predeﬁned macro.

• _ISPA88K predeﬁned macro.

• _ISPPA_RISC predeﬁned macro.

• Partial speciﬁcation of struct and union members.

Function prototypes, struct and union initialization, and the predeﬁned names and , all

of which are ANSI C features, are supported on HP-UX in ANSI mode.

Compile line options are different between HP-UX C and Domain/C. Check the respective

cc(1) page for complete descriptions.

There are other differences between HP-UX C and Domain/C:

• Alignment: All Domain workstations have hardware or software assists to handle

misaligned data. Programs that rely on these features will not run on the Series 800.

• Floating-point exceptions: All Domain workstations, by default, enable invalid

operation, divide by zero, and overﬂow exception traps. Programs that rely on fault

detection, for instance, to enter a fault handler or to terminate execution on

encountering a fault, will ordinarily generate useless output on HP-UX. However, the

PA1.1 math library for the Series 700/800 provides a function fpsetdefaults(3M),

which enables these traps and therefore allows such programs to run as expected. For

more information, see the HP-UX Floating-Point Guide.

• struct layout and alignment, especially bit-ﬁeld, is different.

• float data type: Domain/C optimizes a statement all of whose atoms are float or

ﬂoating-point constants, to be evaluated in float rather than double.

• register declarations: Domain/C completely ignores register declarations, except to

ensure that language constraints are not violated.

• Include ﬁle search rules are different.