.\"

.\" Copyright 1998 by the Massachusetts Institute of Technology.

.\" Copyright (C) 2004-2009 by Daniel Stenberg

.\"

.\" Permission to use, copy, modify, and distribute this

.\" software and its documentation for any purpose and without

.\" fee is hereby granted, provided that the above copyright

.\" notice appear in all copies and that both that copyright

.\" notice and this permission notice appear in supporting

.\" documentation, and that the name of M.I.T. not be used in

.\" advertising or publicity pertaining to distribution of the

.\" software without specific, written prior permission.

.\" M.I.T. makes no representations about the suitability of

.\" this software for any purpose. It is provided "as is"

.\" without express or implied warranty.

.\"

.TH ARES_LIBRARY_INIT 3 "19 May 2009"

.SH NAME

ares_library_init \- c-ares library initialization

.SH SYNOPSIS

.nf

#include <ares.h>

int ares_library_init(int \fIflags\fP)

int ares_library_init_mem(int \fIflags\fP,

void *(*\fIamalloc\fP)(size_t),

void (*\fIafree\fP)(void *ptr),

void (*\fIarealloc\fP)(void *ptr, size_t size))

.fi

.SH DESCRIPTION

.PP

The

.B ares_library_init

function performs initializations internally required by the c-ares

library that must take place before any other function provided by

c-ares can be used in a program.

.PP

This function must be called at least once within the life of a program,

before the program actually executes any other c-ares library function.

Initializations done by this function remain effective until a number of

calls to \fIares_library_cleanup(3)\fP equal to the number of calls to

this function are performed.

.PP

Successive calls to this function do nothing further, only the first

call done when c-ares is in an uninitialized state is actually

effective.

.PP

The

.I flags

parameter is a bit pattern that tells c-ares exactly which features

should be initialized, as described below. Set the desired bits by

ORing the values together. In normal operation you should specify

\fIARES_LIB_INIT_ALL\fP. Don't use any other value unless you are

familiar with it and trying to control some internal c-ares feature.

.PP

The

.B ares_library_init_mem

function allows the caller to provide memory management functions that the

c-ares library will be use instead of \fImalloc(3)\fP, \fIfree(3)\fP and

\fIrealloc(3)\fP.

.PP

.B This function is not thread safe.

You have to call it once the program has started, but this call must be done

before the program starts any other thread. This is required to avoid

potential race conditions in library initialization, and also due to the fact

that \fIares_library_init(3)\fP might call functions from other libraries that

are thread unsafe, and could conflict with any other thread that is already

using these other libraries.

.PP

On Windows platforms, the library user should ensure that \fIWSAStartup()\fP

is called before the c-ares library is initialized and used.

.PP

Win32/64 application DLLs shall not call \fIares_library_init(3)\fP from the

DllMain function. Doing so will produce deadlocks and other problems.

.SH FLAGS

.TP 5

.B ARES_LIB_INIT_ALL

Initialize everything possible. This sets all known bits.

.TP

.B ARES_LIB_INIT_WIN32

Initialize Win32/64 specific libraries.

.TP

.B ARES_LIB_INIT_NONE

Initialize nothing extra. This sets no bit.

.SH RETURN VALUE

Upon successful completion, ares_library_init() will return 0. Otherwise, a

non-zero error number will be returned to indicate the error. Except for

\fIares_strerror(3)\fP, you shall not call any other c-ares function upon

\fIares_library_init(3)\fP failure.

.SH AVAILABILITY

This function was first introduced in c-ares version 1.7.0 along with the

definition of preprocessor symbol \fICARES_HAVE_ARES_LIBRARY_INIT\fP as an

indication of the availability of this function. Its recursive behavior,

which requires a matching number of calls to \fIares_library_cleanup()\fP

in order to deinitialize the library, is present since c-ares version

1.10.0. Earlier versions would deinitialize the library on the first call

to \fIares_library_cleanup()\fP.

.PP

Since the introduction of this function it is absolutely mandatory to

call it for any Win32/64 program using c-ares.

.PP

Non-Win32/64 systems can still use c-ares version 1.7.0 without calling

\fIares_library_init(3)\fP due to the fact that \fIcurrently\fP it is nearly

a do-nothing function on non-Win32/64 platforms at this point.

.SH SEE ALSO

.BR ares_library_cleanup(3),

.BR ares_strerror(3)

.SH AUTHOR

Yang Tse

.PP

Copyright 1998 by the Massachusetts Institute of Technology.

.br

Copyright (C) 2004-2009 by Daniel Stenberg.