This section lists and explains non-functional requirements (a.k.a., quality attributes) of the QP/C Framework.

Standards Compliance

SRS_QP_NF_01

SRS_QP_NF_01 : QP/C Framework shall be implemented in a standardized programming language.
Description A standardized programming language means a language specified by an international standard, such as C99, C11, C++11, C++14, etc.
Rationale A standardized programming language provides a well-defined, documented, and stable set of programming constructs and features.
Forward Traceability

SRS_QP_NF_02

SRS_QP_NF_02 : QP/C Framework shall be implemented in a programming language recommended for safety-critical software.
Description Recommended for safety-critical software means a programming language that is highly recommended for SIL3 and SIL4 according to IEC-61508. For example, the full programming languages like C99 or C++11 are generally not recommended for higher SILs. However, safe subsets of these languages, such as MISRA-C:2023 or MISRA-C++:2023 are highly recommended (see [IEC-61508-3] Table A.3, [IEC-61508-7] C.4.6 Table C.1).
Rationale QP/C Framework shall be certifiable to the international functional safety standards, which require an appropriate implementation programming language.
Forward Traceability

SRS_QP_NF_03

SRS_QP_NF_03 : QP/C Framework shall be modular.
Description QP/C Framework shall apply the following rules: information hiding/encapsulation fully defined interface with explicit specification of function signatures fully documented interfaces modules shall guarantee correct use by preconditions and postconditions (see failure assertion programming) all subprograms (functions) shall have a single entry and a single exit all subprograms (functions) shall have number of parameters limited to 4 all subprograms (functions) shall have complexity limited to 20 (cyclomatic complexity) global variables shall be limited to less than 10 for the whole QP/C Framework
Rationale Modularity is highly recommended by the international functional safety standards.
Forward Traceability SAS_QP_FRM : QP/C Framework layer SDS_QP_QEP : QEP Event Processor QEvt : Event class QEvt::sig : Signal of the event (see Event Signal) ... QEvt::refCtr_ : Event reference counter. ... QEvt::evtTag_ : Event "tag" contains pool-ID plus the Duplicate Inverted Storage of the QEvt::refCtr_ ... QEvt::QEvt_init() : Event without parameters initialization ... QAsm : Abstract State Machine class (state machine interface) QAsm::vptr : Virtual pointer inherited by all QAsm subclasses (see also Object Orientation) ... QAsm::temp : Temporary storage for target/act-table etc. ... QAsm::QAsm_ctor() : Constructor of the QAsm base class ... QHsm : Hierarchical State Machine class (QHsm-style state machine implementation strategy) QHsm::QHsm_ctor() : Constructor of the QHsm base class ... QHsm::QHsm_init_() : Implementation of the top-most initial transition in QHsm ... QHsm::QHsm_dispatch_() : Implementation of dispatching events to a QHsm ... QHsm::QHsm_isIn_() : Check if a given state is part of the current active state configuration ... QHsm::QHsm_state() : Obtain the current active state from a HSM (read only) ... QHsm::QHsm_childState() : Obtain the current active child state of a given parent in QHsm ... QActive : Active object class (based on the QHsm implementation strategy) ... QMsm : Hierarchical State Machine class (QMsm-style state machine implementation strategy) QMsm::QMsm_init_() : Implementation of the top-most initial transition in QMsm ... QMsm::QMsm_dispatch_() : Implementation of dispatching events to a QMsm ... QMsm::QMsm_isIn_() : Tests if a given state is part of the current active state configuration ... QMsm::QMsm_getStateHandler_() : Implementation of getting the state handler in a QMsm subclass ... QMsm::QMsm_stateObj() : Obtain the current state from a MSM (read only) ... QMsm::QMsm_childStateObj() : Obtain the current active child state of a given parent in QMsm ... QMsm::QMsm_ctor() : Constructor of QMsm ... QMsm::QMsm_execTatbl_() : Execute transition-action table ... QMsm::QMsm_exitToTranSource_() : Exit the current state up to the explicit transition source ... QMsm::QMsm_enterHistory_() : Enter history of a composite state ... QMActive : Active object class (based on QMsm implementation strategy) ... SDS_QP_QF : QF Active Object Framework QPSet : Set of Active Objects of up to QF_MAX_ACTIVE elements QSubscrList : Subscriber List (for publish-subscribe) QActive : Active object class (based on the QHsm implementation strategy) QActive::eQueue : Port-dependent event-queue type (often QEQueue) ... QActive::thread : Port-dependent representation of the thread of the active object ... QActive::prio : QF-priority [1..QF_MAX_ACTIVE] of this AO ... QActive::pthre : Preemption-threshold [1..QF_MAX_ACTIVE] of this AO ... QActive::QActive_ctor() : QActive constructor (abstract base class) ... QActive::QActive_start() : Starts execution of an active object and registers the object with the framework ... QActive::QActive_stop() : Stops execution of an active object and removes it from the framework's supervision ... QActive::QActive_post_() : Posts an event `e` directly to the event queue of the active object using the First-In-First-Out (FIFO) policy ... QActive::QActive_postLIFO_() : Posts an event `e` directly to the event queue of the active object using the Last-In-First-Out (LIFO) policy ... QActive::QActive_get_() : Get an event from the event queue of an active object ... QActive::QActive_subscribe() : Subscribes for delivery of signal `sig` to the active object ... QActive::QActive_unsubscribe() : Unsubscribes from the delivery of signal `sig` to the active object ... QActive::QActive_unsubscribeAll() : Unsubscribes from the delivery of all signals to the active object ... QActive::QActive_psInit() : Publish event to all subscribers of a given signal `e->sig` ... QActive::QActive_publish_() : Publish event to all subscribers of a given signal `e->sig` ... QActive::QActive_defer() : Defer an event to a given separate event queue ... QActive::QActive_evtLoop_() : Event loop thread routine for executing an active object `act` (defined some in QP ports) ... QActive::QActive_register_() : Register this active object to be managed by the framework ... QActive::QActive_unregister_() : Un-register the active object from the framework ... QActive::QActive_subscrList_ : Static (one per-class) pointer to all subscriber AOs for a given event signal ... QACTIVE_POST : Invoke the direct event posting facility QActive_post_() ... QACTIVE_POST_X : Invoke the direct event posting facility QActive_post_() without delivery guarantee ... QACTIVE_POST_LIFO : Post an event to an active object using the Last-In-First-Out (LIFO) policy ... QACTIVE_PUBLISH : Publish an event to all subscriber Active Objects ... QMActive : Active object class (based on QMsm implementation strategy) QMActive::QMActive_ctor() : Constructor of QMActive class ... QTicker : "Ticker" Active Object class QTicker::QTicker_ctor() : Constructor of the QTicker Active Object class ... QTicker::QTicker_trig_() : Asynchronously trigger the QTicker active object to perform tick processing ... QTICKER_TRIG : Asynchronously trigger the QTicker AO to perform tick processing ... QF::QF_init() : QF initialization QF::QF_stop() : Invoked by the application layer to stop the QF framework and return control to the OS/Kernel (used in some QF ports) QF::QF_run() : Transfers control to QF to run the application QF::QF_getQueueMin() : This function returns the minimum of free entries of the given event queue QF::QF_onStartup() : Startup QF callback QF::QF_onCleanup() : Cleanup QF callback QF::QF_poolInit() : Event pool initialization for dynamic allocation of events QF::QF_getPoolMin() : Obtain the minimum of free entries of the given event pool QF::QF_newX_() : Internal QF implementation of creating new mutable (dynamic) event QF::QF_gc() : Recycle a mutable (mutable) event QF::QF_newRef_() : Internal QF implementation of creating new event reference QF::QF_deleteRef_() : Internal QF implementation of deleting event reference QF::QF_onContextSw() : QF context switch callback used in built-in kernels (QV/QK/QXK) Q_NEW : Allocate a mutable (dynamic) event Q_NEW_X : Non-asserting allocate a mutable (dynamic) event Q_NEW_REF : Create a new reference of the current event `e` Q_DELETE_REF : Delete the event reference SAS_QP_OSAL : OS abstraction layer (OSAL) SAS_QP_OS : OS layer

SRS_QP_NF_04

SRS_QP_NF_04 : QP/C Framework shall be layered.
Description
Rationale Layered design is highly recommended by the international functional safety standards.
Forward Traceability SAS_QP_FRM : QP/C Framework layer SDS_QP_QEP : QEP Event Processor QEvt : Event class QEvt::sig : Signal of the event (see Event Signal) ... QEvt::refCtr_ : Event reference counter. ... QEvt::evtTag_ : Event "tag" contains pool-ID plus the Duplicate Inverted Storage of the QEvt::refCtr_ ... QEvt::QEvt_init() : Event without parameters initialization ... QAsm : Abstract State Machine class (state machine interface) QAsm::vptr : Virtual pointer inherited by all QAsm subclasses (see also Object Orientation) ... QAsm::temp : Temporary storage for target/act-table etc. ... QAsm::QAsm_ctor() : Constructor of the QAsm base class ... QHsm : Hierarchical State Machine class (QHsm-style state machine implementation strategy) QHsm::QHsm_ctor() : Constructor of the QHsm base class ... QHsm::QHsm_init_() : Implementation of the top-most initial transition in QHsm ... QHsm::QHsm_dispatch_() : Implementation of dispatching events to a QHsm ... QHsm::QHsm_isIn_() : Check if a given state is part of the current active state configuration ... QHsm::QHsm_state() : Obtain the current active state from a HSM (read only) ... QHsm::QHsm_childState() : Obtain the current active child state of a given parent in QHsm ... QActive : Active object class (based on the QHsm implementation strategy) ... QMsm : Hierarchical State Machine class (QMsm-style state machine implementation strategy) QMsm::QMsm_init_() : Implementation of the top-most initial transition in QMsm ... QMsm::QMsm_dispatch_() : Implementation of dispatching events to a QMsm ... QMsm::QMsm_isIn_() : Tests if a given state is part of the current active state configuration ... QMsm::QMsm_getStateHandler_() : Implementation of getting the state handler in a QMsm subclass ... QMsm::QMsm_stateObj() : Obtain the current state from a MSM (read only) ... QMsm::QMsm_childStateObj() : Obtain the current active child state of a given parent in QMsm ... QMsm::QMsm_ctor() : Constructor of QMsm ... QMsm::QMsm_execTatbl_() : Execute transition-action table ... QMsm::QMsm_exitToTranSource_() : Exit the current state up to the explicit transition source ... QMsm::QMsm_enterHistory_() : Enter history of a composite state ... QMActive : Active object class (based on QMsm implementation strategy) ... SDS_QP_QF : QF Active Object Framework QPSet : Set of Active Objects of up to QF_MAX_ACTIVE elements QSubscrList : Subscriber List (for publish-subscribe) QActive : Active object class (based on the QHsm implementation strategy) QActive::eQueue : Port-dependent event-queue type (often QEQueue) ... QActive::thread : Port-dependent representation of the thread of the active object ... QActive::prio : QF-priority [1..QF_MAX_ACTIVE] of this AO ... QActive::pthre : Preemption-threshold [1..QF_MAX_ACTIVE] of this AO ... QActive::QActive_ctor() : QActive constructor (abstract base class) ... QActive::QActive_start() : Starts execution of an active object and registers the object with the framework ... QActive::QActive_stop() : Stops execution of an active object and removes it from the framework's supervision ... QActive::QActive_post_() : Posts an event `e` directly to the event queue of the active object using the First-In-First-Out (FIFO) policy ... QActive::QActive_postLIFO_() : Posts an event `e` directly to the event queue of the active object using the Last-In-First-Out (LIFO) policy ... QActive::QActive_get_() : Get an event from the event queue of an active object ... QActive::QActive_subscribe() : Subscribes for delivery of signal `sig` to the active object ... QActive::QActive_unsubscribe() : Unsubscribes from the delivery of signal `sig` to the active object ... QActive::QActive_unsubscribeAll() : Unsubscribes from the delivery of all signals to the active object ... QActive::QActive_psInit() : Publish event to all subscribers of a given signal `e->sig` ... QActive::QActive_publish_() : Publish event to all subscribers of a given signal `e->sig` ... QActive::QActive_defer() : Defer an event to a given separate event queue ... QActive::QActive_evtLoop_() : Event loop thread routine for executing an active object `act` (defined some in QP ports) ... QActive::QActive_register_() : Register this active object to be managed by the framework ... QActive::QActive_unregister_() : Un-register the active object from the framework ... QActive::QActive_subscrList_ : Static (one per-class) pointer to all subscriber AOs for a given event signal ... QACTIVE_POST : Invoke the direct event posting facility QActive_post_() ... QACTIVE_POST_X : Invoke the direct event posting facility QActive_post_() without delivery guarantee ... QACTIVE_POST_LIFO : Post an event to an active object using the Last-In-First-Out (LIFO) policy ... QACTIVE_PUBLISH : Publish an event to all subscriber Active Objects ... QMActive : Active object class (based on QMsm implementation strategy) QMActive::QMActive_ctor() : Constructor of QMActive class ... QTicker : "Ticker" Active Object class QTicker::QTicker_ctor() : Constructor of the QTicker Active Object class ... QTicker::QTicker_trig_() : Asynchronously trigger the QTicker active object to perform tick processing ... QTICKER_TRIG : Asynchronously trigger the QTicker AO to perform tick processing ... QF::QF_init() : QF initialization QF::QF_stop() : Invoked by the application layer to stop the QF framework and return control to the OS/Kernel (used in some QF ports) QF::QF_run() : Transfers control to QF to run the application QF::QF_getQueueMin() : This function returns the minimum of free entries of the given event queue QF::QF_onStartup() : Startup QF callback QF::QF_onCleanup() : Cleanup QF callback QF::QF_poolInit() : Event pool initialization for dynamic allocation of events QF::QF_getPoolMin() : Obtain the minimum of free entries of the given event pool QF::QF_newX_() : Internal QF implementation of creating new mutable (dynamic) event QF::QF_gc() : Recycle a mutable (mutable) event QF::QF_newRef_() : Internal QF implementation of creating new event reference QF::QF_deleteRef_() : Internal QF implementation of deleting event reference QF::QF_onContextSw() : QF context switch callback used in built-in kernels (QV/QK/QXK) Q_NEW : Allocate a mutable (dynamic) event Q_NEW_X : Non-asserting allocate a mutable (dynamic) event Q_NEW_REF : Create a new reference of the current event `e` Q_DELETE_REF : Delete the event reference SAS_QP_OSAL : OS abstraction layer (OSAL) SAS_QP_OS : OS layer

Determinism

SRS_QP_NF_20

SRS_QP_NF_20 : All services provided by QP/C must be deterministic.
Description Deterministic services means that the service has a well-defined upper bound on the CPU and memory utilization.
Rationale QP/C Framework shall be certifiable to the international functional standards, which require determinism.
Forward Traceability

SRS_QP_NF_21

SRS_QP_NF_21 : All services provided by QP/C shall use limited and known amount of call stack
Description The call stack (or multiple call stacks, if used) is a limited resource taking up a significant portion of the precious RAM in deeply embedded applications targeted by QP/C Framework.
Rationale The stack is a critical resource in that its exhaustion (a.k.a. stack overflow) represents a system failure, rather than merely some degradation of performance. Therefore, it is imperative for QP/C Framework (and QP/C Application by extension) to use the call stack efficiently and deterministically.
Forward Traceability

Portability

SRS_QP_NF_40

SRS_QP_NF_40 : QP/C Framework shall be portable to 16-/32-/64-bit CPUs.
Description QP/C Framework shall be implemented such that
Rationale QP/C Framework shall internally be implemented without implicit assumptions about the CPU register size for correctness of the internal algorithms. Among others, the bit-widths of integer variables must be specified in the implementation, so that they provide adequate dynamic range. Also, integer overflows and underflows (e.g., "wrap-arounds"), if relevant for a given algorithm, need to be handled without assumptions on the CPU register size.
Forward Traceability SAS_OSAL_API : OSAL API

SRS_QP_NF_41

SRS_QP_NF_41 : QP/C Framework shall be portable to a wide range of real-time kernels.
Description As an implementation of the Active Object model of computation, QP/C Framework shall preserve the inherent ability of Active Objects work with a variety of real-time kernels. This includes traditional blocking RTOS kernels, special non-blocking kernels (e.g., QV, QK, QXK), and general-purpose operating systems (POSIX, Windows).
Rationale Portability of QP/C Framework (and QP/C Applications based on the framework) to a wide range of kernels allows applications to use the most appropriate kernel for the job at hand. Additionally, portability to GP-OS allows running and developing and testing QP/C Applications on the host computers.
Forward Traceability SAS_OSAL_API : OSAL API

Ease of Development

SRS_QP_NF_50

SRS_QP_NF_50 : All State Machine Implementation Strategies provided by QP/C Framework shall be easy to debug.
Description "Easy to debug" state machine implementation means that it should always be possible to set a single debugger breakpoint in the code to stop upon the execution of a given state machine element, such as a state transition or entry to a given state, exit from a given state, a given guard condition, etc. An example of a hard to debug implementation would be one in which a given transition or entry to a state would be represented more than once in the code. A single breakpoint would not necessarily be sufficient to guarantee that the breakpoint is reached when that element is executed. Hard to debug state machine implementations are often the result of "flattening" the hierarchical state machine to the non-hierarchical representation, which causes repetitions of transitions.
Rationale The ease of debugging is essential for effective development and maintenance of the state machine code.
Forward Traceability

Constraints

SRS_QP_NF_10

SRS_QP_NF_10 : QP/C Framework implementation shall NOT depend on any standard libraries.
Description
Forward Traceability

SRS_QP_NF_11

SRS_QP_NF_11 : QP/C Framework implementation shall NOT use floating point.
Description
Forward Traceability

SRS_QP_NF_12

SRS_QP_NF_12 : QP/C Framework shall NOT use multiple inheritance.
Description Multiple inheritance is complex and can lead to problems (e.g., problematic diamond-shaped inheritance). Therefore, safe subsets of OO programming languages often disallow use of multiple inheritance.
Forward Traceability

SRS_QP_NF_13

SRS_QP_NF_13 : All services provided by QP/C must NOT use the standard heap.
Description QP/C Framework must not force Applications to use potentially unsafe and indeterministic memory allocation policies, like the standard heap. In other words, the QP/C Framework should internally use only static memory with worst-case memory consumption known at compile-time.

SRS_QP_NF_14

SRS_QP_NF_14 : QP/C Framework shall NOT internally pre-allocate memory for application-specific objects such as event-queue buffers; event-pool buffers; tracing-buffers etc.
Description
Forward Traceability

Preemptive Dual-Mode Kernel