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[library.c]
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 a 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 9899:2024, Annex F131 to the extent applicable to the floating-point types ([basic.fundamental]) that are parameter types of the called function.
[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.
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[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.
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See also ISO/IEC 9899:2024, 7.6.