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Fix the inadvertent libpq ABI breakage discovered by Martin Pitt: the

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renumbering of encoding IDs done between 8.2 and 8.3 turns out to break 8.2
initdb and psql if they are run with an 8.3beta1 libpq.so.  For the moment
we can rearrange the order of enum pg_enc to keep the same number for
everything except PG_JOHAB, which isn't a problem since there are no direct
references to it in the 8.2 programs anyway.  (This does force initdb
unfortunately.)

Going forward, we want to fix things so that encoding IDs can be changed
without an ABI break, and this commit includes the changes needed to allow
libpq's encoding IDs to be treated as fully independent of the backend's.
The main issue is that libpq clients should not include pg_wchar.h or
otherwise assume they know the specific values of libpq's encoding IDs,
since they might encounter version skew between pg_wchar.h and the libpq.so
they are using.  To fix, have libpq officially export functions needed for
encoding name<=>ID conversion and validity checking; it was doing this
anyway unofficially.

It's still the case that we can't renumber backend encoding IDs until the
next bump in libpq's major version number, since doing so will break the
8.2-era client programs.  However the code is now prepared to avoid this
type of problem in future.

Note that initdb is no longer a libpq client: we just pull in the two
source files we need directly.  The patch also fixes a few places that
were being sloppy about checking for an unrecognized encoding name.
This commit is contained in:
Tom Lane
2007-10-13 20:18:42 +00:00
parent 537e92e41f
commit 8468146b03
21 changed files with 194 additions and 81 deletions
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36
src/bin/psql/mbprint.c
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@@ -3,15 +3,45 @@
*
* Copyright (c) 2000-2007, PostgreSQL Global Development Group
*
* $PostgreSQL: pgsql/src/bin/psql/mbprint.c,v 1.25 2007/01/05 22:19:49 momjian Exp $
* $PostgreSQL: pgsql/src/bin/psql/mbprint.c,v 1.26 2007/10/13 20:18:41 tgl Exp $
*
* XXX this file does not really belong in psql/. Perhaps move to libpq?
* It also seems that the mbvalidate function is redundant with existing
* functionality.
*/
#include "postgres_fe.h"
#include "mbprint.h"
#include "libpq-fe.h"
#ifndef PGSCRIPTS
#include "settings.h"
#endif
#include "mbprint.h"
#include "mb/pg_wchar.h"
/*
* To avoid version-skew problems, this file must not use declarations
* from pg_wchar.h: the encoding IDs we are dealing with are determined
* by the libpq.so we are linked with, and that might not match the
* numbers we see at compile time. (If this file were inside libpq,
* the problem would go away...)
*
* Hence, we have our own definition of pg_wchar, and we get the values
* of any needed encoding IDs on-the-fly.
*/
typedef unsigned int pg_wchar;
static int
get_utf8_id(void)
{
static int utf8_id = -1;
if (utf8_id < 0)
utf8_id = pg_char_to_encoding("utf8");
return utf8_id;
}
#define PG_UTF8 get_utf8_id()
static pg_wchar
utf2ucs(const unsigned char *c)