ares_library_init_mem missing from ares.h

[Tom Lloyd]

In summary:

Looks like the manual page for c-ares is unclear as to the
availability of the two functions it covers:
ares_library_init
ares_library_init_mem

Secondly the #define only seems to cover availability of:
ares_library_init

I would suggest an update to the manual with the addition of
2. Another page/section for ares_library_init_mem another define
for the ares_library_init_mem function which I am guess came in after 1.10.

----------------------------------------
I am making calls to:

ares_library_init_mem

I am expecting it to compile

However I am getting:

undefined reference to `ares_library_init_mem'

This code is further protected with:
#ifdef CARES_HAVE_ARES_LIBRARY_INIT

see manual page text:
AVAILABILITY
This function was first introduced in c-ares version 1.7.0 along with the definition of preprocessor symbol CARES_HAVE_ARES_LIBRARY_INIT as an indication of the availability of this function. Its recursive behavior, which requires a matching number of calls to ares_library_cleanup() 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 ares_library_cleanup().

Since the introduction of this function it is absolutely mandatory to call it for any Win32/64 program using c-ares.

Non-Win32/64 systems can still use c-ares version 1.7.0 without calling ares_library_init due to the fact that currently it is nearly a do-nothing function on non-Win32/64 platforms at this point.

Found inside ares_versions.h:

#define ARES_VERSION_MAJOR 1
#define ARES_VERSION_MINOR 10
#define ARES_VERSION_PATCH 0
#define ARES_VERSION ((ARES_VERSION_MAJOR<<16)|\
                       (ARES_VERSION_MINOR<<8)|\
                       (ARES_VERSION_PATCH))
#define ARES_VERSION_STR "1.10.0"

#if (ARES_VERSION >= 0x010700)
# define CARES_HAVE_ARES_LIBRARY_INIT 1
# define CARES_HAVE_ARES_LIBRARY_CLEANUP 1
#else
# undef CARES_HAVE_ARES_LIBRARY_INIT
# undef CARES_HAVE_ARES_LIBRARY_CLEANUP
#endif
------------------------------------------
System Info:
lsb_release -rd
Description: Ubuntu 16.04.3 LTS
Release: 16.04

libc-ares-dev:
  Installed: 1.10.0-3ubuntu0.2
  Candidate: 1.10.0-3ubuntu0.2
  Version table:
 *** 1.10.0-3ubuntu0.2 500
        500 http://gb.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages
        100 /var/lib/dpkg/status
     1.10.0-3 500
        500 http://gb.archive.ubuntu.com/ubuntu xenial/main amd64 Packages