CLib Support Library - Thread Safety Hooks for C Library Functions

Overview

The CLib Support Library provides hooks to make C library functions such as malloc and free thread-safe for FreeRTOS and ThreadX RTOSes. It supports GCC Newlib, ARM C library, IAR C library, and LLVM ARM picolibc toolchains, and also implements the standard time() function backed by the microcontroller Real-Time Clock (RTC).

Most application developers will not interact with this library directly; it is automatically included as a dependency of ModusToolbox™ BSPs. For full API documentation, see the Reference Guide.

Public API

Startup Initialization

For GCC, IAR, and LLVM ARM toolchains, the startup code must call cy_toolchain_init() after static data initialization and before static constructors. This is done automatically for PSoC™ devices.

void cy_toolchain_init(void);

Time Functions

When the HAL is present and an RTC-capable device is used, the standard time() function returns seconds elapsed since the epoch, sourced from the microcontroller RTC.

mtb_clib_support_init

/* HAL API version >= 3 */
void mtb_clib_support_init(mtb_hal_rtc_t* rtc);

/* Earlier HAL versions */
void mtb_clib_support_init(cyhal_rtc_t* rtc);

Initializes the CLIB support library with an RTC handle.

Parameter	Type	Description
rtc	mtb_hal_rtc_t* / cyhal_rtc_t*	Pointer to the RTC handle. May be NULL if time() will not be used.

Note: For MTB_HAL_API_VERSION >= 3, mtb_clib_support_init must be called before time() is invoked. If not called, time() will assert (when asserts are enabled) and return a default time value.

mtb_clib_support_get_rtc

/* HAL API version >= 3 */
mtb_hal_rtc_t* mtb_clib_support_get_rtc(void);

/* Earlier HAL versions */
cyhal_rtc_t* mtb_clib_support_get_rtc(void);

Returns a pointer to the RTC handle used by the CLIB support library.

	Type	Description
Returns	mtb_hal_rtc_t* / cyhal_rtc_t*	Pointer to the RTC handle, or NULL if not initialized.

Deprecated macros: cy_set_rtc_instance is replaced by mtb_clib_support_init; cy_get_rtc_instance is replaced by mtb_clib_support_get_rtc.

Setting Up Time Support

To configure time() with an existing RTC handle:

1. Initialize the RTC handle using the PDL API.
2. Write the current time to the RTC using the PDL API.
3. Pass the RTC handle to mtb_clib_support_init().
4. Call time() to retrieve the current time.

Features

The library provides the following C library hook implementations:

GCC Newlib: _sbrk, __malloc_lock, __malloc_unlock, __env_lock, __env_unlock

ARM C library: _platform_post_stackheap_init, __user_perthread_libspace, _mutex_initialize, _mutex_acquire, _mutex_release, _mutex_free, _sys_exit, $Sub$$_sys_open, _ttywrch, _sys_command_string

IAR C library: __aeabi_read_tp (FreeRTOS), _reclaim_reent, __iar_system_Mtxinit (FreeRTOS), __iar_system_Mtxlock (FreeRTOS), __iar_system_Mtxunlock (FreeRTOS), __iar_system_Mtxdst (FreeRTOS), __iar_file_Mtxinit, __iar_file_Mtxlock, __iar_file_Mtxunlock, __iar_file_Mtxdst, __iar_Initdynamiclock, __iar_Lockdynamiclock, __iar_Unlockdynamiclock, __iar_Dstdynamiclock, __close, __lseek, remove

LLVM ARM picolibc: __retarget_lock_init_recursive, __retarget_lock_init, __retarget_lock_close_recursive, __retarget_lock_close, __retarget_lock_acquire_recursive, __retarget_lock_acquire, __retarget_lock_release_recursive, __retarget_lock_release, __aeabi_errno_addr, _exit

C++: __cxa_guard_acquire, __cxa_guard_abort, __cxa_guard_release

Time: time() from <time.h>, backed by the microcontroller RTC (when HAL is present)

For reference documentation on the hook interfaces defined by each toolchain, see:

• ARM: Multithreaded support in ARM C libraries
• GCC Newlib: malloc lock documentation
• IAR: IAR EWARM Development Guide
• LLVM ARM picolibc: Locking documentation

Requirements

FreeRTOS

The following options must be enabled in FreeRTOSConfig.h:

• configUSE_MUTEXES
• configUSE_RECURSIVE_MUTEXES
• configSUPPORT_STATIC_ALLOCATION

To enable Thread Local Storage for GCC Newlib, also enable configUSE_NEWLIB_REENTRANT.

ThreadX

The following option must be enabled:

• TX_DISABLE_REDUNDANT_CLEARING

When building with IAR:

• The --threaded_lib linker argument must be provided (done automatically with psoc6make 1.3.1 and later).
• TX_ENABLE_IAR_LIBRARY_SUPPORT must be defined in the application to enable the ThreadX IAR-specific port for clib thread safety.

For more information about porting with ThreadX, see the ThreadX GitHub.

LLVM ARM

LLVM ARM (picolibc) is currently supported for use with FreeRTOS only.

Note: The picolibc printf implementation does not provide thread safety for streams shared between multiple threads. Applications must implement their own synchronization for printf in multithreaded contexts.

Related Middleware and Dependencies

This library is used by:

• secure-sockets - TLS/TCP socket abstraction; uses clib-support for RTC-backed system time during certificate validation
• wifi-core-freertos-lwip-mbedtls - Wi-Fi middleware core stack (FreeRTOS + lwIP + Mbed TLS)
• ethernet-core-freertos-lwip-mbedtls - Ethernet middleware core stack (FreeRTOS + lwIP + Mbed TLS)
• mtb-template-cat5 - ModusToolbox project template for CAT5 devices

This library depends on:

• FreeRTOS or ThreadX - RTOS providing mutex and thread management (one required)

Release Notes and Changelog

• RELEASE.md - Detailed release notes for all versions

License

• LICENSE - Apache License 2.0 (applies to all source code)
• EULA - Infineon End User License Agreement

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Copyright

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