[alt.headers]

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

## 16.4 Library-wide requirements [[requirements]](requirements#alt.headers)

### 16.4.5 Constraints on programs [[constraints]](constraints#alt.headers)

#### 16.4.5.4 Headers [alt.headers]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L3384)

If a file with a name
equivalent to the derived file name for one of the C++ standard library headers
is not provided as part of the implementation, and a file with that name
is placed in any of the standard places for a source file to be [included](cpp.include "15.3 Source file inclusion [cpp.include]"),
the behavior is undefined[.](#1.sentence-1)