24.16. Task Stack Allocator Configuration — RTEMS Classic API Guide 5.4-rc2 (21st August 2026) documentation

# 24.16. Task Stack Allocator Configuration

This section describes configuration options related to the task stack allocator. RTEMS allows the application or BSP to define its own allocation and deallocation methods for task stacks. This can be used to place task stacks in special areas of memory or to utilize a Memory Management Unit so that stack overflows are detected in hardware.

## 24.16.1. CONFIGURE_TASK_STACK_ALLOCATOR

CONSTANT:

  `CONFIGURE_TASK_STACK_ALLOCATOR`

OPTION TYPE:

  This configuration option is an initializer define.

DEFAULT VALUE:

  The default value is `_Workspace_Allocate`, which indicates that task stacks will be allocated from the RTEMS Workspace.

VALUE CONSTRAINTS:

  The value of this configuration option shall be defined to a valid function pointer of the type `void *( *allocate )( size_t )`.

DESCRIPTION:

  The value of this configuration option initializes the stack allocator allocate handler.

NOTES:

  A correctly configured system shall configure the following to be consistent:

  - CONFIGURE_TASK_STACK_ALLOCATOR_INIT

  - CONFIGURE_TASK_STACK_ALLOCATOR

  - CONFIGURE_TASK_STACK_DEALLOCATOR

## 24.16.2. CONFIGURE_TASK_STACK_ALLOCATOR_INIT

CONSTANT:

  `CONFIGURE_TASK_STACK_ALLOCATOR_INIT`

OPTION TYPE:

  This configuration option is an initializer define.

DEFAULT VALUE:

  The default value is `NULL`.

VALUE CONSTRAINTS:

  The value of this configuration option shall be defined to a valid function pointer of the type `void ( *initialize )( size_t )` or to `NULL`.

DESCRIPTION:

  The value of this configuration option initializes the stack allocator initialization handler.

NOTES:

  A correctly configured system shall configure the following to be consistent:

  - CONFIGURE_TASK_STACK_ALLOCATOR_INIT

  - CONFIGURE_TASK_STACK_ALLOCATOR

  - CONFIGURE_TASK_STACK_DEALLOCATOR

## 24.16.3. CONFIGURE_TASK_STACK_DEALLOCATOR

CONSTANT:

  `CONFIGURE_TASK_STACK_DEALLOCATOR`

OPTION TYPE:

  This configuration option is an initializer define.

DEFAULT VALUE:

  The default value is `_Workspace_Free`, which indicates that task stacks will be allocated from the RTEMS Workspace.

VALUE CONSTRAINTS:

  The value of this configuration option shall be defined to a valid function pointer of the type `void ( *deallocate )( void * )`.

DESCRIPTION:

  The value of this configuration option initializes the stack allocator deallocate handler.

NOTES:

  A correctly configured system shall configure the following to be consistent:

  - CONFIGURE_TASK_STACK_ALLOCATOR_INIT

  - CONFIGURE_TASK_STACK_ALLOCATOR

  - CONFIGURE_TASK_STACK_DEALLOCATOR

## 24.16.4. CONFIGURE_TASK_STACK_FROM_ALLOCATOR

CONSTANT:

  `CONFIGURE_TASK_STACK_FROM_ALLOCATOR`

OPTION TYPE:

  This configuration option is an initializer define.

DEFAULT VALUE:

  The default value is a macro which supports the system heap allocator.

VALUE CONSTRAINTS:

  The value of this configuration option shall be defined to a macro which accepts exactly one parameter and returns an unsigned integer. The parameter will be an allocation size and the macro shall return this size plus the overhead of the allocator to manage an allocation request for this size.

DESCRIPTION:

  The value of this configuration option is used to calculate the task stack space size.

NOTES:

  This configuration option may be used if a custom task stack allocator is configured, see CONFIGURE_TASK_STACK_ALLOCATOR.

## 24.16.5. CONFIGURE_TASK_STACK_ALLOCATOR_AVOIDS_WORK_SPACE

CONSTANT:

  `CONFIGURE_TASK_STACK_ALLOCATOR_AVOIDS_WORK_SPACE`

OPTION TYPE:

  This configuration option is a boolean feature define.

DEFAULT CONFIGURATION:

  If this configuration option is undefined, then the described feature is not enabled.

DESCRIPTION:

  In case this configuration option is defined, then the system is informed that the task stack allocator does not use the RTEMS Workspace.

NOTES:

  This configuration option may be used if a custom task stack allocator is configured, see CONFIGURE_TASK_STACK_ALLOCATOR.

## 24.16.6. CONFIGURE_TASK_STACK_ALLOCATOR_FOR_IDLE

CONSTANT:

  `CONFIGURE_TASK_STACK_ALLOCATOR_FOR_IDLE`

OPTION TYPE:

  This configuration option is an initializer define.

DEFAULT VALUE:

  The default value is `_Stack_Allocator_allocate_for_idle`, which indicates that IDLE task stacks will be allocated from an area statically reserved by <rtems/confdefs.h>`.

VALUE CONSTRAINTS:

  The value of this configuration option shall be defined to a valid function pointer of the type `void *( *allocate )( uint32_t, size_t )`.

DESCRIPTION:

  The value of this configuration option is the address for the the IDLE stack allocator allocate handler.

NOTES:

  This configuration option is independent of the other thread stack allocator configuration options. It is assumed that any memory allocated for IDLE task stacks will not be from the RTEMS Workspace or the memory statically reserved by default.