diff --git a/.github/workflows/config.yml b/.github/workflows/config.yml
index 9b9fac88..863ef081 100644
--- a/.github/workflows/config.yml
+++ b/.github/workflows/config.yml
@@ -23,6 +23,9 @@ jobs:
           - DOCKER_IMAGE: debian:stretch
           - DOCKER_IMAGE: osrf/ubuntu_armhf:trusty
           - DOCKER_IMAGE: osrf/ubuntu_armhf:xenial
+          - DOCKER_IMAGE: debian:sid
+          - DOCKER_IMAGE: debian:sid
+            USE_EXPERIMENTAL: TRUE
       fail-fast: false
 
     runs-on: ubuntu-latest
@@ -42,10 +45,11 @@ jobs:
           export TRAVIS_BRANCH=${GITHUB_REF#refs/heads/}
           export TRAVIS_OS_NAME=linux
           export DOCKER_IMAGE=${{matrix.DOCKER_IMAGE}}
-          if [[ "$DOCKER_IMAGE" == *"arm"* ]]; then sudo apt-get install -y -qq qemu-user-static git; fi
+          export USE_EXPERIMENTAL=${{matrix.USE_EXPERIMENTAL}}
+          if [[ "$DOCKER_IMAGE" == *"arm"* ]]; then sudo apt update -y -qq && sudo apt-get install -y -qq qemu-user-static git; fi
           if [[ "$DOCKER_IMAGE" == *"arm64v8"* ]]; then export QEMU_VOLUME="-v /usr/bin/qemu-aarch64-static:/usr/bin/qemu-aarch64-static"; export PLATFORM_OPTION="--platform linux/aarch64"; fi #
           echo "Testing branch $TRAVIS_BRANCH of $REPOSITORY_NAME"
-          docker run $PLATFORM_OPTION --rm $QEMU_VOLUME -v $CI_SOURCE_PATH:$CI_SOURCE_PATH -e "DOCKER_IMAGE=$DOCKER_IMAGE" -e "COLLISION_LIB=$COLLISION_LIB" -e "CI_SOURCE_PATH=$CI_SOURCE_PATH" -e "HOME=$HOME" -t $DOCKER_IMAGE sh -c "cd $CI_SOURCE_PATH; ./.travis.sh"
+          docker run $PLATFORM_OPTION --rm $QEMU_VOLUME -v $CI_SOURCE_PATH:$CI_SOURCE_PATH -e "DOCKER_IMAGE=$DOCKER_IMAGE" -e "COLLISION_LIB=$COLLISION_LIB" -e "USE_EXPERIMENTAL=$USE_EXPERIMENTAL" -e "CI_SOURCE_PATH=$CI_SOURCE_PATH" -e "HOME=$HOME" -t $DOCKER_IMAGE sh -c "cd $CI_SOURCE_PATH; ./.travis.sh"
 
   linux-arm:
     strategy:
diff --git a/.travis.sh b/.travis.sh
index 14a68340..90402169 100755
--- a/.travis.sh
+++ b/.travis.sh
@@ -22,7 +22,7 @@ function travis_time_end {
 
 travis_time_start setup.apt-get_update
 # Use archive repository for Debian Stretch
-if [[ "$DOCKER_IMAGE" == *"stretch" ]]; then
+if [[ "$DOCKER_IMAGE" == *"stretch" || "$DOCKER_IMAGE" == *"buster" ]]; then
     sed -i 's/[[:alpha:]]*.debian.org/archive.debian.org/' /etc/apt/sources.list
     sed -i '/stretch-updates/ s/^#*/#/' /etc/apt/sources.list
 fi
@@ -36,6 +36,13 @@ echo 'debconf debconf/frontend select Noninteractive' | sudo debconf-set-selecti
 #
 sudo apt-get install -qq -y git make gcc g++ libjpeg-dev libxext-dev libx11-dev libgl1-mesa-dev libglu1-mesa-dev libpq-dev libpng-dev xfonts-100dpi xfonts-75dpi pkg-config libbullet-dev  # msttcorefonts could not install on 14.04 travis
 # sudo apt-get install -qq -y texlive-latex-base ptex-bin latex2html nkf poppler-utils || echo "ok" # 16.04 does ont have ptex bin
+
+# test with latest GCC's
+if [[ "$USE_EXPERIMENTAL" == "true" ]]; then
+    echo 'deb http://deb.debian.org/debian experimental main' | sudo tee /etc/apt/sources.list.d/experimental.list
+    apt update -qq -y
+    apt-get -qq  -y -t=experimental install gcc g++
+fi
 travis_time_end
 
 if [[ "$COLLISION_LIB" != "" ]]; then
diff --git a/irteus/Makefile b/irteus/Makefile
index 51fed4ae..ab6d8798 100644
--- a/irteus/Makefile
+++ b/irteus/Makefile
@@ -159,7 +159,7 @@ all: defun.h $(LIBNR) $(LIBIRTEUS) $(LIBIRTEUSG) $(LIBIRTEUSX) $(LIBIRTEUSIMG) $
 
 .PHONY: defun.h
 defun.h:
-	echo '#include "eus.h"\n#undef defun\npointer TEST();\nvoid test(void) {register context *ctx; pointer mod; defun(ctx,"TEST",mod,TEST,NULL);}' > test.c
+	echo '#include "eus.h"\n#undef defun\npointer TEST();\nvoid test(void) {register context *ctx; pointer mod; defun((context *)ctx,(char *)"TEST",(pointer)mod,(pointer(*)(context*,int,pointer*))TEST,(char *)NULL);}' > test.c
 	echo "// redefine defun for update defun() API () https://github.com/euslisp/EusLisp/pull/116" > defun.h
 	echo "#undef defun" >> defun.h
 	$(CC) $(CFLAGS) $(WFLAGS) -c test.c $(OBJOPT) test.o || echo "#define defun(a, b, c, d, e) defun(a, b, c, d) // for EusLisp < 9.24" >> defun.h
diff --git a/irteus/eusbullet.c b/irteus/eusbullet.c
index ad12be03..ab92861b 100644
--- a/irteus/eusbullet.c
+++ b/irteus/eusbullet.c
@@ -45,9 +45,9 @@
 
 #include "eus.h"
 
-extern pointer ___eusbullet();
+extern pointer ___eusbullet(context*,int,pointer*);
 static void register_eusbullet()
-{ add_module_initializer("___eusbullet", ___eusbullet);}
+{ add_module_initializer("___eusbullet", (pointer (*)(context*,int,pointer*))___eusbullet);}
 
 extern eusinteger_t C_BT_MakeSphereModel(eusfloat_t r);
 extern eusinteger_t C_BT_MakeBoxModel(eusfloat_t xsize, eusfloat_t ysize, eusfloat_t zsize);
diff --git a/irteus/euspng.c b/irteus/euspng.c
index 2f69e547..17f4c7b4 100644
--- a/irteus/euspng.c
+++ b/irteus/euspng.c
@@ -46,9 +46,9 @@
 #include <png.h>
 #include "eus.h"
 
-extern pointer ___euspng();
+extern pointer ___euspng(context*,int,pointer*);
 static void register_euspng()
-{ add_module_initializer("___euspng", ___euspng);}
+{ add_module_initializer("___euspng", (pointer (*)(context*,int,pointer*))___euspng);}
 
 pointer PNG_READ_IMAGE(register context *ctx, int n, register pointer *argv)
 {
diff --git a/irteus/euspqp.c b/irteus/euspqp.c
index 4d925073..aa5fd233 100644
--- a/irteus/euspqp.c
+++ b/irteus/euspqp.c
@@ -45,9 +45,9 @@
 
 #include "eus.h"
 
-extern pointer ___euspqp();
+extern pointer ___euspqp(context*,int,pointer*);
 static void register_euspqp()
-{ add_module_initializer("___euspqp", ___euspqp);}
+{ add_module_initializer("___euspqp", (pointer (*)(context*,int,pointer*))___euspqp);}
 
 extern eusinteger_t PQP_MakeModel();
 extern void PQP_DeleteModel(eusinteger_t m);
diff --git a/irteus/irtc.c b/irteus/irtc.c
index 1f56065d..80faf80e 100644
--- a/irteus/irtc.c
+++ b/irteus/irtc.c
@@ -44,9 +44,9 @@
 #include "eus.h"
 #include "nr.h"
 #include <math.h>
-extern pointer ___irtc();
+extern pointer ___irtc(context*,int,pointer*);
 static void register_irtc()
-{ add_module_initializer("___irtc", ___irtc);}
+{ add_module_initializer("___irtc", (pointer (*)(context*,int,pointer*))___irtc);}
 
 #define colsize(p) (intval(p->c.ary.dim[1]))
 #define rowsize(p) (intval(p->c.ary.dim[0]))
@@ -1029,11 +1029,10 @@ register pointer *argv;
 }
 
 #include "defun.h" // redefine defun for update defun() API
-pointer ___irtc(ctx,n,argv, env)
+pointer ___irtc(ctx,n,argv)
 register context *ctx;
 int n;
 pointer argv[];
-pointer env;
 {
   pointer mod=argv[0];
   defun(ctx,"ROTM3*",mod,MATTIMES3,NULL);
diff --git a/irteus/irtgeoc.c b/irteus/irtgeoc.c
index 5203b017..d5324b63 100644
--- a/irteus/irtgeoc.c
+++ b/irteus/irtgeoc.c
@@ -2,9 +2,9 @@
 #include "eus.h"
 #include <math.h>
 
-extern pointer ___irtgeoc();
+extern pointer ___irtgeoc(context*,int,pointer*);
 static void register_irtgeoc()
-{ add_module_initializer("___irtgeoc", ___irtgeoc);}
+{ add_module_initializer("___irtgeoc", (pointer (*)(context*,int,pointer*))___irtgeoc);}
 
 //
 //
@@ -355,8 +355,8 @@ pointer C_ISNAN (ctx,n,argv)
 }
 
 #include "defun.h" // redefine defun for update defun() API
-pointer ___irtgeoc(ctx,n, argv, env)
-     register context *ctx;int n;pointer *argv;pointer env;
+pointer ___irtgeoc(ctx,n, argv)
+     register context *ctx;int n;pointer *argv;
 {
   defun(ctx,"C-COORDS-TRANSFORM-VECTOR",argv[0],C_COORDS_TRNSFORM_VECTOR,NULL);
   defun(ctx,"C-MATRIX-ROW",argv[0],C_MATRIX_ROW,NULL);
diff --git a/irteus/irtglc.c b/irteus/irtglc.c
index 218b2057..1e01cc24 100644
--- a/irteus/irtglc.c
+++ b/irteus/irtglc.c
@@ -46,9 +46,9 @@
 
 #include "eus.h"
 
-extern pointer ___irtglc();
+extern pointer ___irtglc(context*,int,pointer*);
 static void register_irtglc()
-{ add_module_initializer("___irtglc", ___irtglc);}
+{ add_module_initializer("___irtglc", (pointer (*)(context*,int,pointer*))___irtglc);}
 
 #define colsize(p) (intval(p->c.ary.dim[1]))
 #define rowsize(p) (intval(p->c.ary.dim[0]))
@@ -89,11 +89,10 @@ pointer CTRANSPOSE_IMAGE_ROWS(ctx,n,argv)
     return((pointer)dst);}}
 
 #include "defun.h" // redefine defun for update defun() API
-pointer ___irtglc(ctx,n,argv,env)
+pointer ___irtglc(ctx,n,argv)
      register context *ctx;
      int n;
      pointer argv[];
-     pointer env;
 {
   pointer mod=argv[0];
   defun(ctx,"CTRANSPOSE-IMAGE-ROWS",mod,CTRANSPOSE_IMAGE_ROWS,NULL);