Update.

2000-07-28  Philip Blundell  <philb@gnu.org>

	* math/test-fpucw.c: Ignore reserved bits in control word.

2000-07-28  Philip Blundell  <philb@gnu.org>

	* sysdeps/unix/sysv/linux/arm/sysdep.h (PSEUDO_RET): New macro.
	(ret): Redefine to PSEUDO_RET.
	(PSEUDO): Remove jump to syscall_error.

2000-07-29  Mark Kettenis  <kettenis@gnu.org>

	* resolv/README: Add some information about using the resolver in
	multi-threaded code and with C++.  Spelling fixes.

2000-07-29  Mark Kettenis  <kettenis@gnu.org>

	* resolv/resolv.h (struct __sockaddr_in): Remove.
	(struct __res_state) [!_LIBC]: Remove reference to __sockaddr_in.

	* sysdeps/powerpc/backtrace.c (struct layout): Make pointers
	__unbounded.

1 files changed, 72 insertions, 2 deletions

diff --git a/resolv/README b/resolv/README
index e862fffe57..416205da77 100644
--- a/resolv/README
+++ b/resolv/README
@@ -1,3 +1,6 @@
+The resolver in the GNU C Library
+*********************************
+
 Starting with version 2.2, the resolver in the GNU C Library comes
 from BIND 8.  Only a subset of the src/lib/resolv part of libbind is
 included here; basically the parts that are needed to provide the
@@ -30,11 +33,78 @@ The resolver in the GNU C Library still differs from what's in BIND
 * The `res_close' function in glibc only tries to close open files
   referenced through `_res' if the RES_INIT bit is set in
   `_res.options'.  This fixes a potential security bug with programs
-  that bogusly call `res_close' without initializing the resolver
+  that bogusly call `res_close' without initialising the resolver
   state first.  Note that the thread-safe `res_nclose' still doesn't
   check the RES_INIT bit.  By the way, you're not really supposed to
   call `res_close/res_nclose' directly.
 
+* The resolver in glibc can connect to a nameserver over IPv6.  Just
+  specify the IPv6 address in /etc/resolv.conf.  You cannot change the
+  address of an IPv6 nameserver dynamically in your program though.
+
+
+Using the resolver in multi-threaded code
+=========================================
+
+The traditional resolver interfaces `res_query', `res_search',
+`res_mkquery', `res_send' and `res_init', used a static (global)
+resolver state stored in the `_res' structure.  Therefore, these
+interfaces are not thread-safe.  Therefore, BIND 8.2 introduced a set
+of "new" interfaces `res_nquery', `res_nsearch', `res_nmkquery',
+`res_nsend' and `res_ninit' that take a `res_state' as their first
+argument, so you can use a per-thread resolver state.  In glibc, when
+you link with -lpthread, such a per-thread resolver state is already
+present.  It can be accessed using `_res', which has been redefined as
+a macro, in a similar way to what has been done for the `errno' and
+`h_errno' variables.  This per-thread resolver state is also used for
+the `gethostby*' family of functions, which means that for example
+`gethostbyname_r' is now fully thread-safe and re-entrant.  The
+traditional resolver interfaces however, continue to use a single
+resolver state and are therefore still thread-unsafe.  The resolver
+state is the same resolver state that is used for the initial ("main")
+thread.  
+
+This has the following consequences for existing binaries and source
+code:
+
+* Single-threaded programs will continue to work.  There should be no
+  user-visible changes when you recompile them.
+
+* Multi-threaded programs that use the traditional resolver interfaces
+  in the "main" thread should continue to work, except that they no
+  longer see any changes in the global resolver state caused by calls
+  to, for example, `gethostbyname' in other threads.  Again there
+  should be no user-visible changes when you recompile these programs.
+
+* Multi-threaded programs that use the traditional resolver interfaces
+  in more than one thread should be just as buggy as before (there are
+  no problems if you use proper locking of course).  If you recompile
+  these programs, manipulating the _res structure in threads other
+  than the "main" thread will seem to have no effect though.
+
+* In Multi-threaded that manipulate the _res structure, calls to
+  functions like `gethostbyname' in threads other than the "main"
+  thread won't be influenced by the those changes anymore.  So if you
+  set RES_USE_INET6, a call to `gethostbyname' won't return any IPv6
+  hosts anymore.  If you recompile such programs, manipulating the
+  _res structure will affect the thread in which you do so instead of
+  the "main" thread.
+
+We recommend to use the new thread-safe interfaces in new code, since
+the traditional interfaces have been deprecated by the BIND folks.
+For compatibility with other (older) systems you might want to
+continue to use those interfaces though.
+
+
+Using the resolver in C++ code
+==============================
+
+There resolver contains some hooks which will allow the user to
+install some callback functions that make it possible to filter DNS
+requests and responses.  Although we do not encourage you to make use
+of this facility at all, C++ developers should realise that it isn't
+safe to throw exceptions from such callback functions.
+
 
 Source code
 ===========
@@ -78,7 +148,7 @@ src/lib/inet/
 src/lib/isc/
   base64.c
 
-Some of these files have been optimized a bit, and adaptations have
+Some of these files have been optimised a bit, and adaptations have
 been made to make them fit in with the rest of glibc.  The more
 non-obvious changes are wrapped in something like `#ifdef _LIBC'.