[namespace.posix]

# 16 Library introduction [[library]](./#library)

## 16.4 Library-wide requirements [[requirements]](requirements#namespace.posix)

### 16.4.5 Constraints on programs [[constraints]](constraints#namespace.posix)

#### 16.4.5.2 Namespace use [[namespace.constraints]](namespace.constraints#namespace.posix)

#### 16.4.5.2.2 Namespace posix [namespace.posix]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L3107)

The behavior of a C++ program is undefined if it adds declarations or definitions to namespaceposix or to a namespace within namespaceposix unless otherwise specified[.](#1.sentence-1)

The namespace posix is reserved for use by
ISO/IEC/IEEE 9945 and other POSIX standards[.](#1.sentence-2)