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QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
Programming
Programmer's Guide
The QNX OS Programmer's Guide covers a variety of topics that might interest developers who are building applications that will run under the QNX OS.
Freedom from Hardware and Platform Dependencies
The QNX OS can run on many different hardware platforms. The way in which applications can access peripheral devices and how data is stored varies between platforms. This chapter explains our solutions for minimizing the impact of such platform dependencies.
Solutions
Now that we've seen the problems, let's take a look at some of the solutions you can use.
Determining endianness
The file <gulliver.h> contains macros to help resolve endian issues.

QNX Momentics IDE User's Guide
This User's Guide describes version 8.0 of the Integrated Development Environment (IDE) that's part of the QNX Tool Suite.
QNX Software Development Platform
QNX SDP is a cross-compiling and debugging environment, including an IDE and command-line tools, for building binary images and programs for target boards running the QNX OS 8.0.
- Quickstart Guide
- System Architecture
  The System Architecture guide accompanies the QNX OS and is intended for both application developers and end-users.
- OS Components & Operations
- Graphics
- Programming
  - Getting Started with the QNX OS
    Getting Started with the QNX OS: A Guide for Realtime Programmers is intended to introduce you to the QNX OS and help you develop applications and resource managers for it.
  - Programmer's Guide
    The QNX OS Programmer's Guide covers a variety of topics that might interest developers who are building applications that will run under the QNX OS.
    - Compiling and Debugging
      Let's start by looking at some things you should consider when you start to write a program for the QNX OS.
    - QNX OS Architecture and Concepts
      The QNX OS architecture consists of the microkernel and several cooperating processes. These processes communicate with each other via various forms of interprocess communication (IPC). Message passing is the primary form of IPC in QNX OS.
    - Processes
      Your applications should be written in a way that reflects the architecture of the QNX OS—as a set of cooperating processes. In this chapter, we see how to start processes (also known as creating processes) from code, how to terminate them, and how to detect their termination.
    - Multicore Processing
      Multiprocessing systems, whether discrete or multicore, can greatly improve your applications' performance.
    - Working with Access Control Lists (ACLs)
      Some filesystems, such as the Power-Safe (fs-qnx6.so) and QNX compressed filesystems, extend file permissions with Access Control Lists, which are based on the withdrawn IEEE POSIX 1003.1e and 1003.2c draft standards.
    - Understanding the Microkernel's Concept of Time
      Whether you're working with timers or simply getting the time of day, it's important that you understand how the OS works with time.
    - Handling Hardware Interrupts
      This chapter explains the QNX OS mechanisms for quickly reacting to hardware events.
    - Working with Memory
      (or The Persistence of Memory, with a nod to Salvador Dali) In the Process Manager chapter of the System Architecture guide, we looked at how the OS manages memory. This chapter describes how you can work with memory.
    - Freedom from Hardware and Platform Dependencies
      The QNX OS can run on many different hardware platforms. The way in which applications can access peripheral devices and how data is stored varies between platforms. This chapter explains our solutions for minimizing the impact of such platform dependencies.
      - Common problems
        With the advent of multiplatform support, which involves non-x86 platforms as well as peripheral chipsets across these multiple platforms, we don't want to have to write different versions of device drivers for each and every platform.
      - Solutions
        Now that we've seen the problems, let's take a look at some of the solutions you can use.
        Determining endianness
        The file <gulliver.h> contains macros to help resolve endian issues.
        Swapping data if required
        Suppose you need to ensure that data obtained in the host order (i.e., whatever is native on this machine) is returned in a particular order, either big- or little-endian. Or vice versa: you want to convert data from host order to big- or little-endian.
        Accessing unaligned data
        To access data on nonaligned boundaries, you have to access the data one byte at a time (the correct endian order is preserved during byte access).
        Examples
        Here are some examples showing how to access different pieces of data using the macros introduced so far.
        Accessing I/O ports
        When you're porting code that accesses hardware, the x86 architecture has a set of instructions that manipulate a separate address space called the I/O address space. This address space is completely separate from the memory address space. On non-x86 platforms, such an address space doesn't exist—all devices are mapped into memory.
    - Conventions for Recursive Makefiles and Directories
      In this chapter, we'll look at the supplementary files used in the QNX OS development environment. Although we use the standard make command to create libraries and executables, we also use some of our own conventions in the Makefile syntax.
    - Glossary
  - Writing a Resource Manager
- System Security Guide
  The QNX System Security Guide is intended for both system integrators who are responsible for the security of a QNX OS system and developers who want to create a QNX OS resource manager free from vulnerabilities.
- Utilities & Libraries
- Migrating to QNX OS 8.0
QNX Software in the Cloud
QNX Software in the Cloud enables developers to use the QNX OS in the Amazon cloud environment.
QNX Toolkit for Visual Studio Code
This User's Guide describes the QNX^® Toolkit for Visual Studio Code. The guide introduces you to the QNX Toolkit by explaining the QNX development environment and how to build, run, and debug your QNX^® Operating System (OS) applications and systems.
QNX Hypervisor User's Guide
This User's Guide explains the QNX hypervisor architecture and provides instructions for installing and running a QNX Hypervisor system, changing system components and configuration, and using hypervisor features such as virtual devices (vdevs).
Typographical Conventions, Support, and Licensing
This section describes the typographical conventions used throughout the documentation, explains how to obtain technical support, and provides some information about licensing.

Determining endianness

QNX SDP8.0Programmer's GuideDeveloper

The file <gulliver.h> contains macros to help resolve endian issues.

The first thing you may need to know is the target system's endianness, which you can find out via the following macros:

__LITTLEENDIAN__: defined if little-endian
__BIGENDIAN__: defined if big-endian

A common coding style in the header files (e.g., <gulliver.h>) is to check which macro is defined and to report an error if none is defined:

#if defined(__LITTLEENDIAN__)
// do whatever for little-endian
#elif defined(__BIGENDIAN__)
// do whatever for big-endian
#else
#error ENDIAN Not defined for system
#endif

The #error statement will cause the compiler to generate an error and abort the compilation.

Page updated: March 05, 2025