*** ./replace.c.ORIG	Thu Jun 30 09:36:53 2011
--- ./replace.c	Thu Jun 30 09:39:44 2011
***************
*** 104,110 ****
  #include "missing_d/usleep.c"
  #endif
  
! #ifndef HAVE_SETENV
  #include "missing_d/setenv.c"
  #endif
  
--- 104,110 ----
  #include "missing_d/usleep.c"
  #endif
  
! #if !defined(HAVE_SETENV) || (defined(HAVE_SETENV) && defined(_AIX51))
  #include "missing_d/setenv.c"
  #endif
  
*** ./support/dfa.c.ORIG	Wed Nov 15 19:32:44 2017
--- ./support/dfa.c	Wed Nov 15 19:37:45 2017
***************
*** 24,31 ****
  
  #include <assert.h>
  #include <ctype.h>
! #ifndef VMS
  #include <stdint.h>
  #else
  #define SIZE_MAX __INT32_MAX
  #define PTRDIFF_MAX __INT32_MAX
--- 24,39 ----
  
  #include <assert.h>
  #include <ctype.h>
! #if !(defined(VMS) || (defined(_AIX) && !defined(_AIX52)))
  #include <stdint.h>
+ #elif (defined(_AIX) && !defined(_AIX52))
+  #if (__64BIT__)
+  #define PTRDIFF_MAX     INT64_MAX
+  #define SIZE_MAX        UINT64_MAX
+  #else
+  #define PTRDIFF_MAX     INT32_MAX
+  #define SIZE_MAX        UINT32_MAX
+  #endif
  #else
  #define SIZE_MAX __INT32_MAX
  #define PTRDIFF_MAX __INT32_MAX
*** ./support/localeinfo.h.ORIG	Wed Nov 15 19:47:19 2017
--- ./support/localeinfo.h	Wed Nov 15 19:47:30 2017
***************
*** 20,26 ****
--- 20,31 ----
  /* Written by Paul Eggert.  */
  
  #include <limits.h>
+ #ifdef HAVE_STDBOOL_H
  #include <stdbool.h>
+ #else
+ #include "missing_d/gawkbool.h"
+ #endif
+ 
  #include <wchar.h>
  
  struct localeinfo
*** ./support/regex_internal.c.ORIG	Tue May 28 10:20:43 2019
--- ./support/regex_internal.c	Tue May 28 10:22:04 2019
***************
*** 135,140 ****
--- 135,148 ----
  
  /* Helper functions for re_string_allocate, and re_string_construct.  */
  
+ #if defined(_AIX) && !defined(_AIX52)
+ #if (__64BIT__)
+ #define SIZE_MAX        UINT64_MAX
+ #else
+ #define SIZE_MAX        UINT32_MAX
+ #endif
+ #endif
+ 
  static reg_errcode_t
  __attribute_warn_unused_result__
  re_string_realloc_buffers (re_string_t *pstr, Idx new_buf_len)
*** ./missing_d/timegm.c.ORIG	Tue May 28 10:29:15 2019
--- ./missing_d/timegm.c	Tue May 28 10:29:29 2019
***************
*** 3,8 ****
--- 3,12 ----
  
  /* timegm -- based on Linux timegm man page */
  
+ #ifndef unsetenv
+ extern int unsetenv( const char *name );
+ #endif
+ 
  time_t
  timegm(struct tm *tm)
  {
*** ./debug.c.ORIG	Tue May 28 10:27:47 2019
--- ./debug.c	Tue May 28 10:28:13 2019
***************
*** 2771,2776 ****
--- 2771,2780 ----
  
  /* debug_prog --- debugger entry point */
  
+ #ifndef unsetenv
+ extern int unsetenv( const char *name );
+ #endif
+ 
  int
  debug_prog(INSTRUCTION *pc)
  {
*** ./str_array.c.ORIG	Tue May 28 10:29:46 2019
--- ./str_array.c	Tue May 28 10:29:57 2019
***************
*** 772,777 ****
--- 772,781 ----
  
  /* env_remove --- for ENVIRON, remove value from real environment */
  
+ #ifndef unsetenv
+ extern int unsetenv( const char *name );
+ #endif
+ 
  static NODE **
  env_remove(NODE *symbol, NODE *subs)
  {
*** ./builtin.c.ORIG	Tue May 28 10:24:55 2019
--- ./builtin.c	Tue May 28 10:25:36 2019
***************
*** 4207,4212 ****
--- 4207,4216 ----
  
  /* format_nan_inf --- format NaN and INF values */
  
+ #if defined(_AIX) && !defined(_AIX52)
+ extern int signbit( double val );
+ #endif
+ 
  char *
  format_nan_inf(NODE *n, char format)
  {