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.. _errors:

Error handling
==============

In libuv errors are negative numbered constants. As a rule of thumb, whenever
there is a status parameter, or an API functions returns an integer, a negative
number will imply an error.

When a function which takes a callback returns an error, the callback will never
be called.

.. note::
    Implementation detail: on Unix error codes are the negated `errno` (or `-errno`), while on
    Windows they are defined by libuv to arbitrary negative numbers.


Error constants
---------------

.. c:macro:: UV_E2BIG

    argument list too long

.. c:macro:: UV_EACCES

    permission denied

.. c:macro:: UV_EADDRINUSE

    address already in use

.. c:macro:: UV_EADDRNOTAVAIL

    address not available

.. c:macro:: UV_EAFNOSUPPORT

    address family not supported

.. c:macro:: UV_EAGAIN

    resource temporarily unavailable

.. c:macro:: UV_EAI_ADDRFAMILY

    address family not supported

.. c:macro:: UV_EAI_AGAIN

    temporary failure

.. c:macro:: UV_EAI_BADFLAGS

    bad ai_flags value

.. c:macro:: UV_EAI_BADHINTS

    invalid value for hints

.. c:macro:: UV_EAI_CANCELED

    request canceled

.. c:macro:: UV_EAI_FAIL

    permanent failure

.. c:macro:: UV_EAI_FAMILY

    ai_family not supported

.. c:macro:: UV_EAI_MEMORY

libuv/docs/src/errors.rst  view on Meta::CPAN

    text file is busy

.. c:macro:: UV_EXDEV

    cross-device link not permitted

.. c:macro:: UV_UNKNOWN

    unknown error

.. c:macro:: UV_EOF

    end of file

.. c:macro:: UV_ENXIO

    no such device or address

.. c:macro:: UV_EMLINK

    too many links


API
---

.. c:function:: UV_ERRNO_MAP(iter_macro)

    Macro that expands to a series of invocations of `iter_macro` for
    each of the error constants above. `iter_macro` is invoked with two
    arguments: the name of the error constant without the `UV_` prefix,
    and the error message string literal.

.. c:function:: const char* uv_strerror(int err)

    Returns the error message for the given error code.  Leaks a few bytes
    of memory when you call it with an unknown error code.

.. c:function:: char* uv_strerror_r(int err, char* buf, size_t buflen)

    Returns the error message for the given error code. The zero-terminated
    message is stored in the user-supplied buffer `buf` of at most `buflen` bytes.

    .. versionadded:: 1.22.0

.. c:function:: const char* uv_err_name(int err)

    Returns the error name for the given error code.  Leaks a few bytes
    of memory when you call it with an unknown error code.

.. c:function:: char* uv_err_name_r(int err, char* buf, size_t buflen)

    Returns the error name for the given error code. The zero-terminated
    name is stored in the user-supplied buffer `buf` of at most `buflen` bytes.

    .. versionadded:: 1.22.0

.. c:function:: int uv_translate_sys_error(int sys_errno)

   Returns the libuv error code equivalent to the given platform dependent error
   code: POSIX error codes on Unix (the ones stored in `errno`), and Win32 error
   codes on Windows (those returned by `GetLastError()` or `WSAGetLastError()`).

   If `sys_errno` is already a libuv error, it is simply returned.

   .. versionchanged:: 1.10.0 function declared public.