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title: "noexcept (C++) | Microsoft Docs"
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# noexcept (C++)
**C++11:** Specifies whether a function might throw exceptions.
## Syntax
> *noexcept-expression*:
> **noexcept**
> **noexcept(** *constant-expression* **)**
### Parameters
*constant-expression*
A constant expression of type `bool` that represents whether the set of potential exception types is empty. The unconditional version is equivalent to `noexcept(true)`.
## Remarks
A *noexcept expression* is a kind of *exception specification*, a suffix to a function declaration that represents a set of types that might be matched by an exception handler for any exception that exits a function. Unary conditional operator `noexcept(`*constant_expression*`)` where *constant_expression* yeilds `true`, and its unconditional synonym `noexcept`, specify that the set of potential exception types that can exit a function is empty. That is, the function never throws an exception and never allows an exception to be propagated outside its scope. The operator `noexcept(`*constant_expression*`)` where *constant_expression* yeilds `false`, or the absence of an exception specification (other than for a destructor or deallocation function), indicates that the set of potential exceptions that can exit the function is the set of all types.
Mark a function as `noexcept` only if all the functions that it calls, either directly or indirectly, are also `noexcept` or `const`. The compiler does not necessarily check every code path for exceptions that might bubble up to a `noexcept` function. If an exception does exit the outer scope of a function marked `noexcept`, [std::terminate](../standard-library/exception-functions.md#terminate) is invoked immediately, and there is no guarantee that destructors of any in-scope objects will be invoked. Use `noexcept` instead of the dynamic exception specifier `throw()`, which is now deprecated in the standard. We recommended you apply `noexcept` to any function that never allows an exception to propagate up the call stack. When a function is declared `noexcept`, it enables the compiler to generate more efficient code in several different contexts. For more information, see [Exception specifications](exception-specifications-throw-cpp.md).
## Example
A template function that copies its argument might be declared `noexcept` on the condition that the object being copied is a plain old data type (POD). Such a function could be declared like this:
```cpp
#include