[support.contract.violation]

# 17 Language support library [[support]](./#support)

## 17.10 Contract-violation handling [[support.contract]](support.contract#violation)

### 17.10.3 Class contract_violation [support.contract.violation]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4491)

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]](basic.contract.eval "6.11.2 Evaluation"))[.](#1.sentence-1)

Objects of this type can
be created only by the implementation[.](#1.sentence-2)

It isimplementation-defined
whether the destructor is virtual[.](#1.sentence-3)

[🔗](#itemdecl:1)

`const char* comment() const noexcept;
`

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4509)

*Returns*: Animplementation-definedntmbs in
the ordinary literal encoding ([[lex.charset]](lex.charset "5.3.1 Character sets"))[.](#2.sentence-1)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4516)

*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[.](#3.sentence-1)

[*Note [1](#note-1)*:

The string can represent a
truncated, reformatted, or summarized rendering of the
predicate, before or after preprocessing[.](#3.sentence-2)

— *end note*]

[🔗](#itemdecl:2)

`contracts::detection_mode detection_mode() const noexcept;
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4536)

*Returns*: The enumerator value
corresponding to
the manner in which the contract violation was identified[.](#4.sentence-1)

[🔗](#itemdecl:3)

`exception_ptr evaluation_exception() const noexcept;
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4550)

*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[.](#5.sentence-1)

[🔗](#itemdecl:4)

`bool is_terminating() const noexcept;
`

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4566)

*Returns*: true if the evaluation semantic is
a terminating semantic ([[basic.contract.eval]](basic.contract.eval "6.11.2 Evaluation"));
otherwise, false[.](#6.sentence-1)

[🔗](#itemdecl:5)

`assertion_kind kind() const noexcept;
`

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4579)

*Returns*: The enumerator value
corresponding to
the syntactic form of the violated contract assertion[.](#7.sentence-1)

[🔗](#itemdecl:6)

`source_location location() const noexcept;
`

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4592)

*Returns*: A source_location object
withimplementation-defined
value[.](#8.sentence-1)

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4599)

*Recommended practice*: The value returned should be
a default constructed source_location object
or a value identifying the violated contract assertion:

- [(9.1)](#9.1)

  When possible,
if the violated contract assertion was a precondition,
the source location of the function invocation should be returned[.](#9.1.sentence-1)

- [(9.2)](#9.2)

  Otherwise,
the source location of the contract assertion should be returned[.](#9.2.sentence-1)

[🔗](#itemdecl:7)

`evaluation_semantic semantic() const noexcept;
`

[10](#10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/support.tex#L4622)

*Returns*: The enumerator value
corresponding to
the evaluation semantic with which
the violated contract assertion was evaluated[.](#10.sentence-1)