Public bug reported:
Binary package hint: manpages-posix-dev
Writing an application that looks up IPv6 addresses, I noticed use of
NULL for the hints field of getaddrinfo() as decribed in the manpage
does not correspond with implementation.
Extracted the source as follows:
$ apt-get source libc6-dev
$ cd glibc-2.5
$ tar xjf glibc-2.5.tar.bz2
$ vi glibc-2.5/sysdeps/posix/getaddrinfo.c
The default_hints structure on line 132 has ai_flags = AI_DEFAULT.
AI_DEFAULTS expands to: (AI_V4MAPPED | AI_ADDRCONFIG)
This is used within getaddrinfo() line 1874 when hints is NULL.
However the manpage states:
"If hints is a null pointer, the behavior shall be as if it referred to a
structure containing the value zero for the ai_flags, ai_socktype, and
ai_protocol fields, and AF_UNSPEC for the ai_family field."
The problem is that behaviour is not that of a zero ai_flags, but instead that
of:
ai_flags = AI_V4MAPPED | AI_ADDRCONFIG
The quick solution is to adjust the manpage to reflect the existing
implementation. Perhaps report it in the manpage's bugs section and
suggest the user always populate hints with a non-NULL value so your
application is more portable.
However the more important question would be what is the correct
implementation?
The Solaris 10 manpage states:
"If the third argument to getaddrinfo() is a null pointer, it is as if the
caller had filled in an addrinfo structure initialized to 0 with ai_family set
to PF_UNSPEC."
Since both manpages suggest a NULL hints is the same as a hints with all
fields zero, the implementation in glibc may have a bug.
** Affects: manpages-posix (Ubuntu)
Importance: Undecided
Status: New
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getaddrinfo manpage doesn't match glibc implementation when hints is NULL
https://bugs.launchpad.net/bugs/153571
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