diff --git a/ChangeLog b/ChangeLog
index 3182cd159..9f6099ef1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,9 @@
 	* backend/bh.c backend/coolscan.c: Minor conversion fixes (from
 	  Andrea Suatoni <a.suatoni@telefonica.net>).
 	* backend/test.c: Use "Color pattern" consistantly.
+	* acinclude.m4 aclocal.m4 configure configure.in 
+	  include/sane/config.h.in: Declare prototypes for all functions that
+	  may miss on some platforms.
 
 2003-01-24  Gerhard Jaeger <gerhard@gjaeger.de>
 	* doc/plustek/Plustek-USB-TODO.txt
diff --git a/acinclude.m4 b/acinclude.m4
index a4ba695ab..fd077863d 100644
--- a/acinclude.m4
+++ b/acinclude.m4
@@ -12,6 +12,7 @@ dnl   JAPHAR_GREP_CFLAGS(flag, cmd_if_missing, cmd_if_present)
 dnl   SANE_LINKER_RPATH
 dnl   SANE_CHECK_U_TYPES
 dnl   SANE_CHECK_GPHOTO2
+dnl   SANE_PROTOTYPES
 dnl   AC_PROG_LIBTOOL
 dnl
 
@@ -342,6 +343,72 @@ AC_DEFUN([SANE_CHECK_GPHOTO2],
 ])	fi
 ])
 
+#
+# Generate prototypes for functions not available on the system
+AC_DEFUN([SANE_PROTOTYPES],
+[
+AH_BOTTOM([
+
+/* Prototype for getenv */
+#ifndef HAVE_GETENV
+char * getenv(const char *name);
+#endif
+
+/* Prototype for inet_ntop */
+#ifndef HAVE_INET_NTOP
+#include <sys/types.h>
+const char * inet_ntop (int af, const void *src, char *dst, size_t cnt);
+#endif
+
+/* Prototype for inet_pton */
+#ifndef HAVE_INET_PTON
+int inet_pton (int af, const char *src, void *dst);
+#endif
+
+/* Prototype for isfdtype */
+#ifndef HAVE_ISFDTYPE
+int isfdtype(int fd, int fdtype);
+#endif
+
+/* Prototype for sigprocmask */
+#ifndef HAVE_SIGPROCMASK
+int sigprocmask (int how, int *new, int *old);
+#endif
+
+/* Prototype for snprintf */
+#ifndef HAVE_SNPRINTF
+#include <sys/types.h>
+int snprintf (char *str,size_t count,const char *fmt,...);
+#endif
+
+/* Prototype for strdup */
+#ifndef HAVE_STRDUP
+char *strdup (const char * s);
+#endif
+
+/* Prototype for strndup */
+#ifndef HAVE_STRNDUP
+#include <sys/types.h>
+char *strndup(const char * s, size_t n);
+#endif
+
+/* Prototype for strsep */
+#ifndef HAVE_STRSEP
+char *strsep(char **stringp, const char *delim);
+#endif
+
+/* Prototype for usleep */
+#ifndef HAVE_USLEEP
+unsigned int usleep (unsigned int useconds);
+#endif
+
+/* Prototype for vsyslog */
+#ifndef HAVE_VSYSLOG
+#include <stdarg.h>
+void vsyslog(int priority, const char *format, va_list args);
+#endif
+])
+])
 
 # libtool.m4 - Configure libtool for the host system. -*-Shell-script-*-
 ## Copyright 1996, 1997, 1998, 1999, 2000, 2001
diff --git a/aclocal.m4 b/aclocal.m4
index c152d3cce..5e5ea7c5c 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -24,6 +24,7 @@ dnl   JAPHAR_GREP_CFLAGS(flag, cmd_if_missing, cmd_if_present)
 dnl   SANE_LINKER_RPATH
 dnl   SANE_CHECK_U_TYPES
 dnl   SANE_CHECK_GPHOTO2
+dnl   SANE_PROTOTYPES
 dnl   AC_PROG_LIBTOOL
 dnl
 
@@ -354,6 +355,72 @@ AC_DEFUN([SANE_CHECK_GPHOTO2],
 ])	fi
 ])
 
+#
+# Generate prototypes for functions not available on the system
+AC_DEFUN([SANE_PROTOTYPES],
+[
+AH_BOTTOM([
+
+/* Prototype for getenv */
+#ifndef HAVE_GETENV
+char * getenv(const char *name);
+#endif
+
+/* Prototype for inet_ntop */
+#ifndef HAVE_INET_NTOP
+#include <sys/types.h>
+const char * inet_ntop (int af, const void *src, char *dst, size_t cnt);
+#endif
+
+/* Prototype for inet_pton */
+#ifndef HAVE_INET_PTON
+int inet_pton (int af, const char *src, void *dst);
+#endif
+
+/* Prototype for isfdtype */
+#ifndef HAVE_ISFDTYPE
+int isfdtype(int fd, int fdtype);
+#endif
+
+/* Prototype for sigprocmask */
+#ifndef HAVE_SIGPROCMASK
+int sigprocmask (int how, int *new, int *old);
+#endif
+
+/* Prototype for snprintf */
+#ifndef HAVE_SNPRINTF
+#include <sys/types.h>
+int snprintf (char *str,size_t count,const char *fmt,...);
+#endif
+
+/* Prototype for strdup */
+#ifndef HAVE_STRDUP
+char *strdup (const char * s);
+#endif
+
+/* Prototype for strndup */
+#ifndef HAVE_STRNDUP
+#include <sys/types.h>
+char *strndup(const char * s, size_t n);
+#endif
+
+/* Prototype for strsep */
+#ifndef HAVE_STRSEP
+char *strsep(char **stringp, const char *delim);
+#endif
+
+/* Prototype for usleep */
+#ifndef HAVE_USLEEP
+unsigned int usleep (unsigned int useconds);
+#endif
+
+/* Prototype for vsyslog */
+#ifndef HAVE_VSYSLOG
+#include <stdarg.h>
+void vsyslog(int priority, const char *format, va_list args);
+#endif
+])
+])
 
 # libtool.m4 - Configure libtool for the host system. -*-Shell-script-*-
 
diff --git a/configure b/configure
index 3b1ff2c61..e46434762 100755
--- a/configure
+++ b/configure
@@ -8194,6 +8194,10 @@ fi
 done
 
 
+
+
+
+
 if test "$ac_cv_header_os2_h" = "yes" ; then
 
 cat >>confdefs.h <<\_ACEOF
@@ -9469,7 +9473,7 @@ test "x$enable_libtool_lock" != xno && enable_libtool_lock=yes
 case $host in
 *-*-irix6*)
   # Find out which ABI we are using.
-  echo '#line 9472 "configure"' > conftest.$ac_ext
+  echo '#line 9476 "configure"' > conftest.$ac_ext
   if { (eval echo "$as_me:$LINENO: \"$ac_compile\"") >&5
   (eval $ac_compile) 2>&5
   ac_status=$?
@@ -9998,7 +10002,7 @@ chmod -w .
 save_CFLAGS="$CFLAGS"
 CFLAGS="$CFLAGS -o out/conftest2.$ac_objext"
 compiler_c_o=no
-if { (eval echo configure:10001: \"$ac_compile\") 1>&5; (eval $ac_compile) 2>out/conftest.err; } && test -s out/conftest2.$ac_objext; then
+if { (eval echo configure:10005: \"$ac_compile\") 1>&5; (eval $ac_compile) 2>out/conftest.err; } && test -s out/conftest2.$ac_objext; then
   # The compiler can only warn and ignore the option if not recognized
   # So say no if there are warnings
   if test -s out/conftest.err; then
@@ -11830,7 +11834,7 @@ else
     lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<EOF
-#line 11833 "configure"
+#line 11837 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11928,7 +11932,7 @@ else
     lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<EOF
-#line 11931 "configure"
+#line 11935 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
diff --git a/configure.in b/configure.in
index ea055f89e..ad820e417 100644
--- a/configure.in
+++ b/configure.in
@@ -183,6 +183,7 @@ AC_CHECK_FUNCS(atexit inet_addr inet_aton inet_ntoa ioperm mkdir \
     cfmakeraw tcsendbreak strcasecmp strncasecmp _portaccess)
 AC_REPLACE_FUNCS(getenv inet_ntop inet_pton isfdtype sigprocmask snprintf \
     strdup strndup strsep usleep vsyslog)
+SANE_PROTOTYPES
 if test "$ac_cv_header_os2_h" = "yes" ; then
   AC_DEFINE(strncasecmp, strnicmp, [Define for OS/2 only])
   AC_DEFINE(strcasecmp, stricmp, [Define for OS/2 only])
diff --git a/include/sane/config.h.in b/include/sane/config.h.in
index c761e71b5..91fd25815 100644
--- a/include/sane/config.h.in
+++ b/include/sane/config.h.in
@@ -406,3 +406,65 @@
 
 /* Define to `unsigned long' if <sys/types.h> does not define. */
 #undef u_long
+
+
+
+/* Prototype for getenv */
+#ifndef HAVE_GETENV
+char * getenv(const char *name);
+#endif
+
+/* Prototype for inet_ntop */
+#ifndef HAVE_INET_NTOP
+#include <sys/types.h>
+const char * inet_ntop (int af, const void *src, char *dst, size_t cnt);
+#endif
+
+/* Prototype for inet_pton */
+#ifndef HAVE_INET_PTON
+int inet_pton (int af, const char *src, void *dst);
+#endif
+
+/* Prototype for isfdtype */
+#ifndef HAVE_ISFDTYPE
+int isfdtype(int fd, int fdtype);
+#endif
+
+/* Prototype for sigprocmask */
+#ifndef HAVE_SIGPROCMASK
+int sigprocmask (int how, int *new, int *old);
+#endif
+
+/* Prototype for snprintf */
+#ifndef HAVE_SNPRINTF
+#include <sys/types.h>
+int snprintf (char *str,size_t count,const char *fmt,...);
+#endif
+
+/* Prototype for strdup */
+#ifndef HAVE_STRDUP
+char *strdup (const char * s);
+#endif
+
+/* Prototype for strndup */
+#ifndef HAVE_STRNDUP
+#include <sys/types.h>
+char *strndup(const char * s, size_t n);
+#endif
+
+/* Prototype for strsep */
+#ifndef HAVE_STRSEP
+char *strsep(char **stringp, const char *delim);
+#endif
+
+/* Prototype for usleep */
+#ifndef HAVE_USLEEP
+unsigned int usleep (unsigned int useconds);
+#endif
+
+/* Prototype for vsyslog */
+#ifndef HAVE_VSYSLOG
+#include <stdarg.h>
+void vsyslog(int priority, const char *format, va_list args);
+#endif
+