I compiled PHP 4.0.0 under HP-UX 10.20 (no DCE threads installed if that matters) using gcc 2.8.1 and found
and fixed a problem of compiling reentrancy.c under
this system.
My configure line was:

./configure  --prefix=/home/web/php4 \
  --with-config-file-path=/home/web/php4 \
  --with-apache=../apache_1.3.12 \
  --with-mysql \
  --enable-track-vars \
  --enable-bcmath \
  --enable-ftp

Compilation of reentrancy.c caused following compiler problem:
  ====
reentrancy.c: In function `php_localtime_r':
reentrancy.c:53: warning: implicit declaration of function `localtime_r'
reentrancy.c: In function `php_ctime_r':
reentrancy.c:60: warning: implicit declaration of function `ctime_r'
reentrancy.c: In function `php_asctime_r':
reentrancy.c:67: warning: implicit declaration of function `asctime_r'
reentrancy.c: In function `php_gmtime_r':
reentrancy.c:74: warning: implicit declaration of function `gmtime_r'
reentrancy.c: At top level:
reentrancy.c:84: redefinition of `php_localtime_r'
reentrancy.c:52: `php_localtime_r' previously defined here
reentrancy.c:105: redefinition of `php_ctime_r'
reentrancy.c:59: `php_ctime_r' previously defined here
reentrancy.c:123: redefinition of `php_asctime_r'
reentrancy.c:66: `php_asctime_r' previously defined here
reentrancy.c:141: redefinition of `php_gmtime_r'
reentrancy.c:73: `php_gmtime_r' previously defined here
  ====

I found that the problem was caused by a combination of a missing macro definition (-D_REENTRANT) which was not set by the configure script (perhaps because I've no DCE threads installed?) and some wrong lines in php_reentrancy.h. The code in reentrancy.c already tries to workaround the different return types of the reentrant time functions (localtime_r() etc.) with defining special functions just for HP-UX. But because -D_REENTRANT is not set in configure, it doesn't see the existing prototypes of localtime_r() etc. and declares MISSING_*DECL which in turn leads in php_reentrancy.h to the definition of a wrong (i.e. non-HPUX) prototype. Moreover this header file wrongly undefines HAVE_LOCALTIME_R etc. for HP-UX (because this was a attempt to fix the problem?).

Anyway, I was able to fix the problem and now have PHP 4.0.0 working by setting CPPFLAGS before running configure this way:

CPPFLAGS=-D_REENTRANT ; export CPPFLAGS
./configure  --prefix=/home/web/php4 \
  --with-config-file-path=/home/web/php4 \
  --with-apache=../apache_1.3.12 \
  --with-mysql \
  --enable-track-vars \
  --enable-bcmath \
  --enable-ftp

and changing php_reentrancy this way (it's  the output of diff -c):

  ====

*** php_reentrancy.h.orig      Thu May 18 16:34:21 2000
--- php_reentrancy.h    Sun Jun 25 02:40:57 2000
***************
*** 33,54 ****
  #define HAVE_CTIME 1


! #ifdef PHP_HPUX_TIME_R
! #undef HAVE_LOCALTIME_R
! #undef HAVE_ASCTIME_R
! #undef HAVE_CTIME_R
! #undef HAVE_GMTIME_R
! #endif

  #if !defined(HAVE_LOCALTIME_R) && defined(HAVE_LOCALTIME)
  #define PHP_NEED_REENTRANCY 1
  PHPAPI struct tm *php_localtime_r(const time_t *const timep, struct tm *p_tm);
  #else
  #define php_localtime_r localtime_r
  #ifdef MISSING_LOCALTIME_R_DECL
  struct tm *localtime_r(const time_t *const timep, struct tm *p_tm);
  #endif
  #endif


  #if !defined(HAVE_CTIME_R) && defined(HAVE_CTIME)
--- 33,58 ----
  #define HAVE_CTIME 1


! //#ifdef PHP_HPUX_TIME_R
! //#undef HAVE_LOCALTIME_R
! //#undef HAVE_ASCTIME_R
! //#undef HAVE_CTIME_R
! //#undef HAVE_GMTIME_R
! //#endif

  #if !defined(HAVE_LOCALTIME_R) && defined(HAVE_LOCALTIME)
  #define PHP_NEED_REENTRANCY 1
  PHPAPI struct tm *php_localtime_r(const time_t *const timep, struct tm *p_tm);
  #else
+ #ifdef PHP_HPUX_TIME_R
+ PHPAPI struct tm *php_localtime_r(const time_t *const timep, struct tm *p_tm);
+ #else
  #define php_localtime_r localtime_r
  #ifdef MISSING_LOCALTIME_R_DECL
  struct tm *localtime_r(const time_t *const timep, struct tm *p_tm);
  #endif
  #endif
+ #endif


  #if !defined(HAVE_CTIME_R) && defined(HAVE_CTIME)
***************
*** 55,65 ****
--- 59,73 ----
  #define PHP_NEED_REENTRANCY 1
  PHPAPI char *php_ctime_r(const time_t *clock, char *buf);
  #else
+ #ifdef PHP_HPUX_TIME_R
+ PHPAPI char *php_ctime_r(const time_t *clock, char *buf);
+ #else
  #define php_ctime_r ctime_r
  #ifdef MISSING_CTIME_R_DECL
  char *ctime_r(const time_t *clock, char *buf);
  #endif
  #endif
+ #endif


  #if !defined(HAVE_ASCTIME_R) && defined(HAVE_ASCTIME)
***************
*** 66,76 ****
--- 74,88 ----
  #define PHP_NEED_REENTRANCY 1
  PHPAPI char *php_asctime_r(const struct tm *tm, char *buf);
  #else
+ #ifdef PHP_HPUX_TIME_R
+ PHPAPI char *php_asctime_r(const struct tm *tm, char *buf);
+ #else
  #define php_asctime_r asctime_r
  #ifdef MISSING_ASCTIME_R_DECL
  char *asctime_r(const struct tm *tm, char *buf);
  #endif
  #endif
+ #endif


  #if !defined(HAVE_GMTIME_R) && defined(HAVE_GMTIME)
***************
*** 77,85 ****
--- 89,101 ----
  #define PHP_NEED_REENTRANCY 1
  PHPAPI struct tm *php_gmtime_r(const time_t *const timep, struct tm *p_tm);
  #else
+ #ifdef PHP_HPUX_TIME_R
+ PHPAPI struct tm *php_gmtime_r(const time_t *const timep, struct tm *p_tm);
+ #else
  #define php_gmtime_r gmtime_r
  #ifdef MISSING_GMTIME_R_DECL
  struct tm *php_gmtime_r(const time_t *const timep, struct tm *p_tm);
+ #endif
  #endif
  #endif

  =====

I think if configure would set -D_REENTRANT always for HP-UX (whether threads are there or not) and with the above patch for php_reentrancy.h this should work for HP-UX 10.xx regardless whether there are threads or not and always for 11.xx.

regards,
Thomas Wolfram
mailto:thomas@wolfram.net