HP aC++/HP C A.06.20 Programmer's Guide

If you plan to run your program on the same system where you are compiling, you do

not need to use the +DS option. The compiler generates code tuned for your system.

If you plan to run your program on a particular model of the HP-UX system, and that

model is different from the one where you compile your program, use +DSmodel with

either the model number of the target system or the processor name of the target system.

Compiling in Networked Environments

When compiles are performed using diskless workstations or NFS-mounted file systems,

it is important that the default code generation and scheduling are based on the local

host processor. The system model numbers of the hosts where the source or object files

reside do not affect the default code generation and scheduling.

-S

The -S option compiles a program and logs the assembly language output in a

corresponding file with a .s suffix. The -S option is only for displaying the assembler

code. The generated code is not intended to be used as input to the assembler (as).

Example:

The following command compiles prog.C to assembly code rather than to object code,

and puts the assembly code in the file prog.s.

aCC -S prog.C

Data Alignment and Storage

This section describes default data storage allocation and alignment for HP compiler

data types.

Data storage refers to the size of data types, such as bool, short, int, float, and

char*. Data alignment refers to the way the HP compiler aligns data structures in

memory. Data type alignment and storage differences can cause problems when moving

data between systems that have different alignment and storage schemes. These

differences become apparent when a structure is exchanged between systems using

files or inter-process communication. In addition, misaligned data addresses can cause

bus errors when an attempt is made to dereference the address.

For information on unaligned data access, See “Handling Unaligned Data” (page 131).

Table 2-2 lists the size and alignment of the HP compiler data types:

Table 2-2 Size and Alignment of HP Compiler Data Types

AlignmentSize (in bytes)Data Type

1-byte1

bool

char, unsigned char, signed

char

40 Command-Line Options