I'm trying to build 2.3.3 on an older slackware system
that is still libc5 based. (gcc version egcs-2.91.66.1)

configure / make reports errors 
 after stripping warnings the error is reported as:

./Modules/posixmodule.c: In function `posix_openpty':
./Modules/posixmodule.c:2623: `I_PUSH' undeclared 
(first use in this function)
./Modules/posixmodule.c:2623: (Each undeclared 
identifier is reported only once
./Modules/posixmodule.c:2623: for each function it 
appears in.)

pyconfig.h only defined HAVE_DEV_PTMX 

#define HAVE_DEV_PTMX 1
/* #undef HAVE_OPENPTY */
/* #undef HAVE__GETPTY */

(I have a recent 2.4.25-pre6 kernel so I do 
have /dev/ptmx that configure uses to check for
HAVE_DEV_PTMX)

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I have found that I have libbsd.a but
not libutil (that is checked for openpty by configure)

cd /usr/lib
nm -g libbsd.a | grep ' T openpty'
00000000 T openpty

If I create a fake libutil.a as a symlink to libbsd.a
 (ln -s libbsd.a libutil.a)
configure and make run to completion

It would have been "nicer" if configure had looked for
libbsd

looks like configure.in could be modified to
check for libbsd by adding a line like
AC_CHECK_FUNCS(openpty,,
AC_CHECK_LIB(bsd,openpty,[AC_DEFINE(HAVE_OPENPTY) LIB
S="$LIBS -lbsd"]))
after
AC_CHECK_FUNCS(openpty,, AC_CHECK_LIB(util,openpty,
[AC_DEFINE(HAVE_OPENPTY) LIB
S="$LIBS -lutil"]))

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I submitted a patch # 881820
relative to 2.4 

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This should be fixed with patch #881820 now.