16 Library introduction [library]

16.2 The C standard library [library.c]

The C++ standard library also makes available the facilities of the C standard library, suitably adjusted to ensure static type safety.

The descriptions of many library functions rely on the C standard library for the semantics of those functions.

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 an ISO C restrict qualifier) are the same unless otherwise stated.

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

The semantics of a call to a C standard library function evaluated as a core constant expression are those specified in ISO/IEC 9899:2018, Annex F139 to the extent applicable to the floating-point types ([basic.fundamental]) that are parameter types of the called function.

[Note 1:

Annex F specifies the conditions under which floating-point exceptions are raised and the behavior when NaNs and/or infinities are passed as arguments.

— end note]

[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.

— end note]

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