diff -urd crosstool-ng.orig/configure crosstool-ng.new/configure
--- crosstool-ng.orig/configure	2015-11-20 14:03:36.000000000 +0100
+++ crosstool-ng.new/configure	2017-05-27 10:12:40.383087059 +0200
@@ -635,6 +635,7 @@
 lzma
 xz
 kconfig_options
+GPERF_LEN_TYPE
 automake
 LIBTOOLIZE
 LIBTOOL
@@ -5331,6 +5332,27 @@
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_path_automake" >&5
 $as_echo "$ac_cv_path_automake" >&6; }
 automake=$ac_cv_path_automake
+ 
+ 
+#----------------------------------------
+# Gperf 3.1 started generating functions with size_t rather than unsigned int
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for the type used in gperf declarations" >&5
+$as_echo_n "checking for the type used in gperf declarations... " >&6; }
+echo "#include <string.h>" > conftest.gperf.c
+echo "const char * in_word_set(const char *, GPERF_LEN_TYPE);" >> conftest.gperf.c
+echo foo,bar | ${GPERF} -L ANSI-C >> conftest.gperf.c
+if ${CC} -c -o /dev/null conftest.gperf.c -DGPERF_LEN_TYPE='size_t' >/dev/null 2>&1; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: size_t" >&5
+$as_echo "size_t" >&6; }
+             GPERF_LEN_TYPE='size_t'
+elif ${CC} -c -o /dev/null conftest.gperf.c -DGPERF_LEN_TYPE='unsigned int' >/dev/null 2>&1; then :
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: unsigned int" >&5
+$as_echo "unsigned int" >&6; }
+             GPERF_LEN_TYPE='unsigned int'
+else
+  as_fn_error $? "unable to determine gperf len type" "$LINENO" 5
+fi
+rm -f conftest.gperf.c
 
 
 #--------------------------------------------------------------------
diff -urd crosstool-ng.orig/configure.ac crosstool-ng.new/configure.ac
--- crosstool-ng.orig/configure.ac	2015-11-18 06:29:15.000000000 +0100
+++ crosstool-ng.new/configure.ac	2017-05-27 10:00:57.411342197 +0200
@@ -290,6 +290,22 @@
          AC_MSG_ERROR([could not find GNU automake >= 1.10])])])
 AC_SUBST([automake], [$ac_cv_path_automake])
 
+#----------------------------------------
+# Gperf 3.1 started generating functions with size_t rather than unsigned int
+AC_MSG_CHECKING([for the type used in gperf declarations])
+echo "#include <string.h>" > conftest.gperf.c
+echo "const char * in_word_set(const char *, GPERF_LEN_TYPE);" >> conftest.gperf.c
+echo foo,bar | ${GPERF} -L ANSI-C >> conftest.gperf.c
+AS_IF([${CC} -c -o /dev/null conftest.gperf.c -DGPERF_LEN_TYPE='size_t' >/dev/null 2>&1],
+            [AC_MSG_RESULT([size_t])
+             GPERF_LEN_TYPE='size_t'],
+        [${CC} -c -o /dev/null conftest.gperf.c -DGPERF_LEN_TYPE='unsigned int' >/dev/null 2>&1],
+            [AC_MSG_RESULT([unsigned int])
+             GPERF_LEN_TYPE='unsigned int'],
+        [AC_MSG_ERROR([unable to determine gperf len type])])
+rm -f conftest.gperf.c
+AC_SUBST([GPERF_LEN_TYPE])
+
 #--------------------------------------------------------------------
 # Boring again... But still a bit of work to do...
 #--------------------------------------------------------------------
diff -urd crosstool-ng.orig/kconfig/Makefile crosstool-ng.new/kconfig/Makefile
--- crosstool-ng.orig/kconfig/Makefile	2015-11-18 06:29:15.000000000 +0100
+++ crosstool-ng.new/kconfig/Makefile	2017-05-27 10:00:57.411342197 +0200
@@ -6,7 +6,8 @@
 	@true   # Just be silent, you fscking son of a fscking beach...
 
 # Build flags
-CFLAGS = -DCONFIG_=\"CT_\" -DPACKAGE="\"crosstool-NG $(VERSION)\""
+CFLAGS = -DCONFIG_=\"CT_\" -DPACKAGE="\"crosstool-NG $(VERSION)\"" \
+	 -DGPERF_LEN_TYPE="$(gperf_len_type)"
 LDFLAGS = $(INTL_LIBS)
 
 # Compiler flags to use gettext
diff -urd crosstool-ng.orig/kconfig/zconf.gperf crosstool-ng.new/kconfig/zconf.gperf
--- crosstool-ng.orig/kconfig/zconf.gperf	2015-11-18 06:29:15.000000000 +0100
+++ crosstool-ng.new/kconfig/zconf.gperf	2017-05-27 10:00:57.411342197 +0200
@@ -9,7 +9,7 @@
 
 struct kconf_id;
 
-static const struct kconf_id *kconf_id_lookup(register const char *str, register unsigned int len);
+static const struct kconf_id *kconf_id_lookup(register const char *str, register GPERF_LEN_TYPE len);
 
 %%
 mainmenu,	T_MAINMENU,	TF_COMMAND
diff -urd crosstool-ng.orig/Makefile.in crosstool-ng.new/Makefile.in
--- crosstool-ng.orig/Makefile.in	2015-11-19 23:43:15.000000000 +0100
+++ crosstool-ng.new/Makefile.in	2017-05-27 10:00:57.411342197 +0200
@@ -69,6 +69,7 @@
 export readelf         := @READELF@
 export patch           := @PATCH@
 export gperf           := @GPERF@
+export gperf_len_type  := @GPERF_LEN_TYPE@
 export CC              := @CC@
 export CPP             := @CPP@
 export CPPFLAGS        := @CPPFLAGS@