Home
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.
OS Components & Operations
Building Embedded Systems
The Building Embedded Systems guide is intended for developers who are developing or building BSPs for QNX OS embedded systems.
Startup Library
The startup library contains a rich set of routines ranging from high-level functions called by main() to utility functions for performing specific startup tasks.
calc_time_t()

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
  - Boot Optimization Guide
    The Boot Optimization Guide describes techniques you can use to reduce the time from your board's initial power on until you have a fully functional QNX system running on the board.
  - Building Embedded Systems
    The Building Embedded Systems guide is intended for developers who are developing or building BSPs for QNX OS embedded systems.
    - Overview
      QNX systems are built from the QNX OS standard release components, the architecture- and board-specific files provided in QNX BSPs, and customer and third-party components.
    - Working with QNX BSPs
      Before you attempt to write a new BSP or modify an existing one, it is helpful to know how to use a BSP.
    - Initial Program Loaders (IPLs)
      IPLs first set up the minimum environment needed to execute their compiled C code, then find the OS image and load it into memory, and then jump to the QNX startup code.
    - Startup Programs
      The first program to run in a bootable OS image is the startup program; it completes the system configuration, then launches the OS kernel.
    - Kernel Callouts
      Kernel callouts are standalone pieces of code (or code fragments) that the kernel uses to perform hardware-specific functions. These callouts don't need to be statically linked to the kernel.
    - System Page
      The system page contains essential information about the system, including the system page's size, information about the hardware platform (including IRQs and the CPUs), the cache size, and the location of kernel callouts in memory.
    - OS Images
      OS images are files that contains the OS, your executables, and any data files that might be related to your programs.
    - OS Image Buildfiles
      You can edit OS image buildfiles to configure OS images.
    - IPL Library
      The IPL library contains a set of routines for building a custom IPL.
    - Startup Library
      The startup library contains a rich set of routines ranging from high-level functions called by main() to utility functions for performing specific startup tasks.
      - add_cache()
      - add_callout()
      - add_callout_array()
      - add_interrupt()
        Add a new entry to the intrinfo section in the system page.
      - add_interrupt_array()
        Populate the interrupt kernel callout array in the system page.
      - add_ram()
      - add_string()
      - add_typed_string()
      - alloc_qtime()
      - alloc_ram()
      - as_add()
      - as_add_containing()
      - as_default()
      - as_find()
      - as_find_containing()
      - as_info2off()
      - as_off2info()
      - as_set_priority()
      - avoid_ram()
      - calc_time_t()
      - calloc_ram()
      - callout_io_map(), callout_io_map_indirect()
      - callout_memory_map(), callout_memory_map_indirect()
      - callout_register_data()
      - chip_access()
      - chip_done()
      - chip_read*()
        Read one, two, four or eight bytes from the device specified by chip_access().
      - chip_write*()
        Write one, two, four or eight bytes from the device specified by chip_access().
      - copy_memory()
        Copy a chunk of memory from physical memory to another location.
      - del_typed_string()
      - find_startup_info()
      - find_typed_string()
      - handle_common_option()
      - hwi_add_device()
      - hwi_add_inputclk()
      - hwi_add_irq()
      - hwi_add_location()
      - hwi_add_nicaddr()
      - hwi_add_rtc()
      - hwi_alloc_item()
        Add an item structure to the system page hwinfo section.
      - hwi_alloc_tag()
        Add a tag structure to the system page hwinfo section.
      - hwi_find_as()
      - init_asinfo()
        Initialize the asinfo section of the system page.
      - init_cacheattr()
        Initialize board-level caches, and populate the cacheattr member in the system page.
      - init_cpuinfo()
        Populate the cpuinfo data structure in the system page with CPU information.
      - init_hwinfo()
        Initialize the appropriate variant of the hwinfo structure in the system page.
      - init_intrinfo()
        Initialize the intrinfo data structure in the system page.
      - init_mmu()
        Set up the processor for virtual addressing mode by setting up page-mapping hardware and enabling the pager.
      - init_qtime()
        Initialize the qtime data structure in the system page.
      - init_raminfo()
        Determine the location and size of available system RAM and initialize the asinfo structure in the system page.
      - init_smp()
        Initialize SMP functionality.
      - init_syspage_memory() (deprecated)
      - init_system_private()
        Finalize initializations at the end of startup.
      - jtag_reserve_memory()
      - kprintf()
        Display output using the put_char() function you provide (x86 only).
      - print_syspage()
        Print the contents of the system page structures.
      - rtc_time()
      - startup_io_map()
        Gain access to a port or memory-mapped device.
      - startup_io_unmap()
      - startup_memory_map()
      - startup_memory_unmap()
      - timer_diff()
      - timer_ns2tick()
      - timer_start()
      - timer_tick2ns()
      - uncompress()
      - x86_64_cpuid_string()
      - x86_64_cputype()
      - x86_64_fputype()
      - x86_scanmem()
    - Debugging QNX Embedded Systems
      The microkernel architecture of QNX OS means that debugging QNX embedded systems can be different from debugging other embedded systems.
    - Sample Buildfiles
      This appendix contains sample buildfiles that you can modify to support your hardware platform and your implementation requirements.
    - Glossary
  - Customizing a BSP
    While QNX provides Board Support Packages (BSPs) for many common platforms and their individual variants, in some cases, you need a BSP for a board that QNX does not provide. If this is the case, you can modify a QNX BSP or develop your own.
  - Device Publishers Developer's Guide
  - High Availability Framework Developer's Guide
  - High-Performance Networking Stack (io-sock) User's Guide
    This guide contains instructions for implementing and using the QNX OS High-Performance Networking Stack and its manager, io-sock.
  - PCI Server User's Guide
  - Performance Tuning User's Guide
  - QNX Filesystem for Safety User's Guide
  - SMMUMAN User's Guide
  - System Analysis Toolkit (SAT) User's Guide
  - Technotes
  - User's Guide
    The QNX OS User's Guide is intended for all users of a QNX OS system, from system administrators to end users.
- Graphics
- Programming
- 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.

calc_time_t()

QNX SDP8.0Building Embedded SystemsConfigurationDeveloper

Synopsis:

unsigned long calc_time_t(const struct tm *tm);

Description:

Given a struct tm (with values appropriate for the UTC timezone), calculate the value to be placed in the boot_time field of the qtime section.

Returns:

>0: Success

Page updated: August 11, 2025