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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.
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.
Stack allocation
Each thread has its own stack that you can allocate yourself or have the system manage.

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.
      - Starting processes: two methods
        In embedded applications, there are two typical approaches to starting your processes at boot time.
      - Process creation
        The process manager component of procnto is responsible for process creation. If a process wants to create another process, it makes a call to one of the process-creation functions, which then effectively sends a message to the process manager.
      - Process termination
      - Detecting process termination
        In an embedded application, it's often important to detect if any process terminates prematurely and, if so, to handle it.
      - Stack allocation
        Each thread has its own stack that you can allocate yourself or have the system manage.
      - Process privileges
        In systems where security is important, applications should run with the fewest privileges possible. This practice helps reduce the impact of possible compromises and can also help lower the privilege escalation attack surface of the device.
      - Controlling processes via the /proc filesystem
        Implemented by the Process Manager component of procnto, the /proc virtual filesystem lets you access and control the processes and threads running in the system.
    - 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) filesystem, 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.
    - 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 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.
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.

Stack allocation

QNX SDP8.0Programmer's GuideDeveloper

Each thread has its own stack that you can allocate yourself or have the system manage.

The pthread_attr_t structure includes members that specify a new thread's stack address and size; pthread_attr_init() sets the default values, and you can use pthread_attr_setstackaddr() and pthread_attr_setstacksize() to override them. The values of the stack address and size members of this structure control the type of stack allocation that occurs when you create a thread:


Stack address	Stack size	Allocation
NULL	0	Automatic (the default)
NULL	Desired size	Partly automatic
Non-NULL	Size of the allocated area	Manual

Let's compare the types of allocation:

Automatic

The pthread_create() function allocates a stack for the thread. The default size for both x86_64 and AArch64 architectures is 256 KB.

The stack is followed by an inaccessible guard page which helps to detect stack overflow. The guard page exists only in virtual memory; there's no physical memory allocated for it.

When the thread exits, the process manager automatically deallocates the stack.

Partly automatic

The pthread_create() function allocates a stack for the thread of the size you specified rounded up to a multiple of the page size (4 KB) and followed by a guard page.

Manual

The process manager uses the stack that you allocated for the thread. It's up to you to allocate enough space for the thread, and no guard page is provided. The process manager doesn't deallocate the stack when the thread exits.

Note:

If you specify a stack size (for partly automatic or manual allocation), it should be the size that you want plus PTHREAD_STACK_MIN, which is the amount of space that the thread needs for its thread local storage and other overhead.

A process's main thread starts with an automatically allocated 512 KB stack, but it isn't deleted when the main thread goes away (e.g., calls pthread_exit() or is cancelled). The main thread's stack includes the command-line arguments and environment variables, which other threads might still need. To specify the stack size for the main thread, use qcc's -N option.

Page updated: August 09, 2024