10 KiB
[support.contract]
17 Language support library [support]
17.10 Contract-violation handling [support.contract]
17.10.1 Header synopsis [contracts.syn]
The header defines types for reporting information about contract violations ([basic.contract.eval]).
// all freestandingnamespace std::contracts {enum class assertion_kind : unspecified { pre = 1, post = 2, assert = 3}; enum class evaluation_semantic : unspecified { ignore = 1, observe = 2, enforce = 3, quick_enforce = 4}; enum class detection_mode : unspecified { predicate_false = 1, evaluation_exception = 2}; class contract_violation {// no user-accessible constructorpublic: contract_violation(const contract_violation&) = delete; contract_violation& operator=(const contract_violation&) = delete; see below ~contract_violation(); const char* comment() const noexcept; contracts::detection_mode detection_mode() const noexcept; exception_ptr evaluation_exception() const noexcept; bool is_terminating() const noexcept; assertion_kind kind() const noexcept; source_location location() const noexcept; evaluation_semantic semantic() const noexcept; }; void invoke_default_contract_violation_handler(const contract_violation&);}
17.10.2 Enumerations [support.contract.enum]
Recommended practice: For all enumerations in [support.contract.enum], if implementation-defined enumerators are provided, they should have a minimum value of 1000.
The enumerators of assertion_kind correspond to the syntactic forms of a contract assertion ([basic.contract.general]), with meanings listed in Table 44.
Table 44 — Enum assertion_kind [tab:support.contract.enum.kind]
| ð Name |
Meaning |
|---|---|
| ð pre |
A precondition assertion |
| ð post |
A postcondition assertion |
| ð assert |
An assertion-statement |
| ð |
The enumerators of evaluation_semantic correspond to the evaluation semantics with which a contract assertion may be evaluated ([basic.contract.eval]), with meanings listed in Table 45.
Table 45 — Enum evaluation_semantic [tab:support.contract.enum.semantic]
| ð Name |
Meaning |
|---|---|
| ð ignore |
Ignore evaluation semantic |
| ð observe |
Observe evaluation semantic |
| ð enforce |
Enforce evaluation semantic |
| ð quick_enforce |
Quick-enforce evaluation semantic |
| ð |
The enumerators of detection_mode correspond to the manners in which a contract violation can be identified ([basic.contract.eval]), with meanings listed in Table 46.
Table 46 — Enum detection_mode [tab:support.contract.enum.detection]
| ð Name |
Meaning |
|---|---|
| ð predicate_false |
The predicate of the contract assertion evaluated to false or would have evaluated to false. |
| ð evaluation_exception |
An uncaught exception occurred during evaluation of the contract assertion. |
| ð |
17.10.3 Class contract_violation [support.contract.violation]
The class contract_violation defines the type of objects used to represent a contract violation that has been detected during the evaluation of a contract assertion with a particular evaluation semantic ([basic.contract.eval]).
Objects of this type can be created only by the implementation.
It isimplementation-defined whether the destructor is virtual.
const char* comment() const noexcept;
Returns: Animplementation-definedntmbs in the ordinary literal encoding ([lex.charset]).
Recommended practice: The string returned should contain a textual representation of the predicate of the violated contract assertion or an empty string if storing a textual representation is undesired.
[Note 1:
The string can represent a truncated, reformatted, or summarized rendering of the predicate, before or after preprocessing.
â end note]
contracts::detection_mode detection_mode() const noexcept;
Returns: The enumerator value corresponding to the manner in which the contract violation was identified.
exception_ptr evaluation_exception() const noexcept;
Returns: If the contract violation occurred because the evaluation of the predicate exited via an exception, an exception_ptr object that refers to that exception or a copy of that exception; otherwise, a null exception_ptr object.
bool is_terminating() const noexcept;
Returns: true if the evaluation semantic is a terminating semantic ([basic.contract.eval]); otherwise, false.
assertion_kind kind() const noexcept;
Returns: The enumerator value corresponding to the syntactic form of the violated contract assertion.
source_location location() const noexcept;
Returns: A source_location object withimplementation-defined value.
Recommended practice: The value returned should be a default constructed source_location object or a value identifying the violated contract assertion:
-
When possible, if the violated contract assertion was a precondition, the source location of the function invocation should be returned.
-
Otherwise, the source location of the contract assertion should be returned.
evaluation_semantic semantic() const noexcept;
Returns: The enumerator value corresponding to the evaluation semantic with which the violated contract assertion was evaluated.
17.10.4 Invoke default handler [support.contract.invoke]
void invoke_default_contract_violation_handler(const contract_violation& v);
Effects: Invokes the default contract-violation handler ([basic.contract.handler]) with the argument v.