Use of errno by the library

Use of errno by the library
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ChapterÂ 5.Â + Diagnostics + +

Use of errno by the library

+ The C and POSIX standards guarantee that errno + is never set to zero by any library function. + The C++ standard has less to say about when errno + is or isn't set, but libstdc++ follows the same rule and never sets + it to zero. +

+ On the other hand, there are few guarantees about when the C++ library + sets errno on error, beyond what is specified for + functions that come from the C library. + For example, when std::stoi throws an exception of + type std::out_of_range, errno + may or may not have been set to ERANGE. +

+ Parts of the C++ library may be implemented in terms of C library + functions, which may result in errno being set + with no explicit call to a C function. For example, on a target where + operator new uses malloc + a failed memory allocation with operator new might + set errno to ENOMEM. + Which C++ library functions can set errno in this way + is unspecified because it may vary between platforms and between releases. +

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