[library.c]

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

## 16.2 The C standard library [library.c]

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L136)

The C++ standard library also makes available the facilities of the C standard library,suitably adjusted to ensure static type safety[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L141)

The descriptions of many library functions rely on the C standard library for
the semantics of those functions[.](#2.sentence-1)

In some cases,
the signatures specified in this document
may be different from the signatures in the C standard library,
and additional overloads may be declared in this document,
but the behavior and the preconditions
(including any preconditions implied by the use of
a C restrict qualifier)
are the same unless otherwise stated[.](#2.sentence-2)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/lib-intro.tex#L153)

A call to a C standard library function is
a non-constant library call ([[defns.nonconst.libcall]](defns.nonconst.libcall "3.35 non-constant library call"))
if it raises a floating-point exception other than FE_INEXACT[.](#3.sentence-1)

The semantics of a call to a C standard library function
evaluated as a core constant expression
are those specified in ISO/IEC 9899:2024, Annex F[131](#footnote-131 "See also ISO/IEC 9899:2024, 7.6.") to the extent applicable to the floating-point types ([[basic.fundamental]](basic.fundamental "6.9.2 Fundamental types"))
that are parameter types of the called function[.](#3.sentence-2)

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

ISO/IEC 9899:2024, Annex F specifies
the conditions under which floating-point exceptions are raised and
the behavior when NaNs and/or infinities are passed as arguments[.](#3.sentence-3)

— *end note*]

[*Note [2](#note-2)*:

Equivalently, a call to a C standard library function is
a non-constant library call
if errno is set
when math_errhandling & MATH_ERRNO is true[.](#3.sentence-4)

— *end note*]

[131)](#footnote-131)[131)](#footnoteref-131)

See also ISO/IEC 9899:2024, 7.6[.](#footnote-131.sentence-1)