MFH: missing part of the fix for #39795

Author: tony2001

acinclude.m4

@@ -2600,6 +2600,7 @@ AC_DEFUN([PHP_CRYPT_R_STYLE],
   AC_CACHE_CHECK([which data struct is used by crypt_r], php_cv_crypt_r_style,[
     php_cv_crypt_r_style=none
     AC_TRY_COMPILE([
+#define _REENTRANT 1
 #include <crypt.h>
 ],[
 CRYPTD buffer;
@@ -2609,6 +2610,7 @@ php_cv_crypt_r_style=cryptd)
 
     if test "$php_cv_crypt_r_style" = "none"; then
       AC_TRY_COMPILE([
+#define _REENTRANT 1
 #include <crypt.h>
 ],[
 struct crypt_data buffer;
@@ -2619,6 +2621,7 @@ php_cv_crypt_r_style=struct_crypt_data)
 
     if test "$php_cv_crypt_r_style" = "none"; then
       AC_TRY_COMPILE([
+#define _REENTRANT 1
 #define _GNU_SOURCE
 #include <crypt.h>
 ],[

ext/standard/crypt.c

@@ -148,7 +148,7 @@ PHP_FUNCTION(crypt)
 		salt[2] = '\0';
 #endif
 	}
-#ifdef HAVE_CRYPT_R
+#if defined(HAVE_CRYPT_R) && defined(_REENTRANT)
 	{
 #if defined(CRYPT_R_STRUCT_CRYPT_DATA)
 		struct crypt_data buffer;