contract_assert statement(since C++26)| General topics | ||||||||||||||||
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| Function declaration | ||||||||||||||||
| Lambda function expression | ||||||||||||||||
inline specifier | ||||||||||||||||
| Dynamic exception specifications(until C++17*) | ||||||||||||||||
noexcept specifier(C++11) | ||||||||||||||||
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| Boolean -Integer -Floating-point | ||||||||||||||||
| Character -String -nullptr(C++11) | ||||||||||||||||
| User-defined(C++11) | ||||||||||||||||
| Utilities | ||||||||||||||||
| Attributes(C++11) | ||||||||||||||||
| Types | ||||||||||||||||
typedef declaration | ||||||||||||||||
| Type alias declaration(C++11) | ||||||||||||||||
| Casts | ||||||||||||||||
| Memory allocation | ||||||||||||||||
| Classes | ||||||||||||||||
| Class-specific function properties | ||||||||||||||||
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| Special member functions | ||||||||||||||||
| Templates | ||||||||||||||||
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Acontract_assert statement is a contract assertion that may appear in a function or lambda body to verify an internal condition. It ensures the condition holds during execution, triggering a violation (e.g. termination) in debug builds if the condition evaluates tofalse or the evaluation exits via an exception, and can be ignored in release builds for performance.
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contract_assertattr (optional)(predicate); | |||||||||
| attr | - | any number ofattributes |
| predicate | - | boolean expression that should evaluate totrue |
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_contracts | 202502L | (C++26) | Contracts |
Thecontract_assert ensures that vector's norm is positive and eithernormal or subnormal.
template<std::floating_point T>constexprauto normalize(std::array<T,3> vector)noexcept pre(/* is_normalizable(vector) */) post(/* vector: is_normalized(vector) */){auto&[x, y, z]{vector};constauto norm{std::hypot(x, y, z)}; // debug check for normalization safety contract_assert(std::isfinite(norm)&& norm> T(0)); x/= norm, y/= norm, z/= norm; return vector;}
| C++26 feature | Paper(s) | GCC | Clang | MSVC | Apple Clang | EDG eccp | Intel C++ | Nvidia HPC C++ (ex PGI)* | Nvidia nvcc | Cray |
|---|---|---|---|---|---|---|---|---|---|---|
| Contracts (FTM)* | P2900R14 |
| aborts the program if the user-specified condition is nottrue. May be disabled for release builds. (function macro)[edit] | |
| Contract assertions(C++26) | specifies properties that must hold at certain points during execution[edit] |
static_assert declaration(C++11) | performs compile-time assertion checking[edit] |
| function contract specifiers(C++26) | specifies preconditions (pre) and postconditions (post)[edit] |
[[assume(expression)]](C++23) | specifies that theexpression will always evaluate totrue at a given point (attribute specifier)[edit] |
