diff --git a/library/ecp.c b/library/ecp.c
index 15da4a2fea..25af6318cc 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -3641,7 +3641,7 @@ cleanup:
 #if defined(MBEDTLS_TEST_HOOKS)
 
 MBEDTLS_STATIC_TESTABLE
-mbedtls_ecp_variant mbedtls_ecp_get_variant()
+mbedtls_ecp_variant mbedtls_ecp_get_variant(void)
 {
     return MBEDTLS_ECP_VARIANT_WITH_MPI_STRUCT;
 }
diff --git a/programs/fuzz/common.c b/programs/fuzz/common.c
index 75021bb2f0..98aa4037b3 100644
--- a/programs/fuzz/common.c
+++ b/programs/fuzz/common.c
@@ -13,7 +13,7 @@ mbedtls_time_t dummy_constant_time(mbedtls_time_t *time)
 }
 #endif
 
-void dummy_init()
+void dummy_init(void)
 {
 #if defined(MBEDTLS_PLATFORM_TIME_ALT)
     mbedtls_platform_set_time(dummy_constant_time);
diff --git a/programs/fuzz/common.h b/programs/fuzz/common.h
index bc817bd769..094383c7a4 100644
--- a/programs/fuzz/common.h
+++ b/programs/fuzz/common.h
@@ -15,7 +15,7 @@ typedef struct fuzzBufferOffset {
 #if defined(MBEDTLS_HAVE_TIME)
 mbedtls_time_t dummy_constant_time(mbedtls_time_t *time);
 #endif
-void dummy_init();
+void dummy_init(void);
 
 int dummy_send(void *ctx, const unsigned char *buf, size_t len);
 int fuzz_recv(void *ctx, unsigned char *buf, size_t len);
diff --git a/programs/ssl/ssl_context_info.c b/programs/ssl/ssl_context_info.c
index a5f0650322..855b0911fd 100644
--- a/programs/ssl/ssl_context_info.c
+++ b/programs/ssl/ssl_context_info.c
@@ -125,12 +125,12 @@ const char buf_ln_err[] = "Buffer does not have enough data to complete the pars
 /*
  * Basic printing functions
  */
-void print_version()
+void print_version(void)
 {
     printf("%s v%d.%d\n", PROG_NAME, VER_MAJOR, VER_MINOR);
 }
 
-void print_usage()
+void print_usage(void)
 {
     print_version();
     printf("\nThis program is used to deserialize an Mbed TLS SSL session from the base64 code provided\n"
@@ -179,7 +179,7 @@ void printf_err(const char *str, ...)
 /*
  * Exit from the program in case of error
  */
-void error_exit()
+void error_exit(void)
 {
     if (NULL != b64_file) {
         fclose(b64_file);
diff --git a/programs/test/udp_proxy.c b/programs/test/udp_proxy.c
index ac527f2573..685e336e67 100644
--- a/programs/test/udp_proxy.c
+++ b/programs/test/udp_proxy.c
@@ -644,7 +644,7 @@ void delay_packet(packet *delay)
     memcpy(&prev[prev_len++], delay, sizeof(packet));
 }
 
-int send_delayed()
+int send_delayed(void)
 {
     uint8_t offset;
     int ret;
diff --git a/scripts/output_env.sh b/scripts/output_env.sh
index 1d9e0faebe..535613298e 100755
--- a/scripts/output_env.sh
+++ b/scripts/output_env.sh
@@ -105,9 +105,37 @@ echo
 print_version "gcc" "--version" "" "head -n 1"
 echo
 
+if [ -n "${GCC_EARLIEST+set}" ]; then
+    print_version "${GCC_EARLIEST}" "--version" "" "head -n 1"
+else
+    echo " GCC_EARLIEST : Not configured."
+fi
+echo
+
+if [ -n "${GCC_LATEST+set}" ]; then
+    print_version "${GCC_LATEST}" "--version" "" "head -n 1"
+else
+    echo " GCC_LATEST : Not configured."
+fi
+echo
+
 print_version "clang" "--version" "" "head -n 2"
 echo
 
+if [ -n "${CLANG_EARLIEST+set}" ]; then
+    print_version "${CLANG_EARLIEST}" "--version" "" "head -n 2"
+else
+    echo " CLANG_EARLIEST : Not configured."
+fi
+echo
+
+if [ -n "${CLANG_LATEST+set}" ]; then
+    print_version "${CLANG_LATEST}" "--version" "" "head -n 2"
+else
+    echo " CLANG_LATEST : Not configured."
+fi
+echo
+
 print_version "ldd" "--version" "" "head -n 1"
 echo
 
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index c47b767aea..97c01f3034 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -176,7 +176,10 @@ pre_initialize_variables () {
     : ${ARMC6_BIN_DIR:=/usr/bin}
     : ${ARM_NONE_EABI_GCC_PREFIX:=arm-none-eabi-}
     : ${ARM_LINUX_GNUEABI_GCC_PREFIX:=arm-linux-gnueabi-}
-
+    : ${CLANG_LATEST:="clang-latest"}
+    : ${CLANG_EARLIEST:="clang-earliest"}
+    : ${GCC_LATEST:="gcc-latest"}
+    : ${GCC_EARLIEST:="gcc-earliest"}
     # if MAKEFLAGS is not set add the -j option to speed up invocations of make
     if [ -z "${MAKEFLAGS+set}" ]; then
         export MAKEFLAGS="-j$(all_sh_nproc)"
@@ -191,9 +194,7 @@ pre_initialize_variables () {
 
     # Gather the list of available components. These are the functions
     # defined in this script whose name starts with "component_".
-    # Parse the script with sed. This way we get the functions in the order
-    # they are defined.
-    ALL_COMPONENTS=$(sed -n 's/^ *component_\([0-9A-Z_a-z]*\) *().*/\1/p' <"$0")
+    ALL_COMPONENTS=$(compgen -A function component_ | sed 's/component_//')
 
     # Exclude components that are not supported on this platform.
     SUPPORTED_COMPONENTS=
@@ -275,6 +276,10 @@ General options:
 Tool path options:
      --armc5-bin-dir=<ARMC5_bin_dir_path>       ARM Compiler 5 bin directory.
      --armc6-bin-dir=<ARMC6_bin_dir_path>       ARM Compiler 6 bin directory.
+     --clang-earliest=<Clang_earliest_path>     Earliest version of clang available
+     --clang-latest=<Clang_latest_path>         Latest version of clang available
+     --gcc-earliest=<GCC_earliest_path>         Earliest version of GCC available
+     --gcc-latest=<GCC_latest_path>             Latest version of GCC available
      --gnutls-cli=<GnuTLS_cli_path>             GnuTLS client executable to use for most tests.
      --gnutls-serv=<GnuTLS_serv_path>           GnuTLS server executable to use for most tests.
      --gnutls-legacy-cli=<GnuTLS_cli_path>      GnuTLS client executable to use for legacy tests.
@@ -441,9 +446,13 @@ pre_parse_command_line () {
             --armcc) no_armcc=;;
             --armc5-bin-dir) shift; ;; # assignment to ARMC5_BIN_DIR done in pre_parse_command_line_for_dirs
             --armc6-bin-dir) shift; ;; # assignment to ARMC6_BIN_DIR done in pre_parse_command_line_for_dirs
+            --clang-earliest) shift; CLANG_EARLIEST="$1";;
+            --clang-latest) shift; CLANG_LATEST="$1";;
             --error-test) error_test=$((error_test + 1));;
             --except) all_except=1;;
             --force|-f) FORCE=1;;
+            --gcc-earliest) shift; GCC_EARLIEST="$1";;
+            --gcc-latest) shift; GCC_LATEST="$1";;
             --gnutls-cli) shift; GNUTLS_CLI="$1";;
             --gnutls-legacy-cli) shift; GNUTLS_LEGACY_CLI="$1";;
             --gnutls-legacy-serv) shift; GNUTLS_LEGACY_SERV="$1";;
@@ -4023,6 +4032,7 @@ component_test_cmake_shared () {
 
 test_build_opt () {
     info=$1 cc=$2; shift 2
+    $cc --version
     for opt in "$@"; do
           msg "build/test: $cc $opt, $info" # ~ 30s
           make CC="$cc" CFLAGS="$opt -std=c99 -pedantic -Wall -Wextra -Werror"
@@ -4035,14 +4045,45 @@ test_build_opt () {
     done
 }
 
-component_test_clang_opt () {
+# For FreeBSD we invoke the function by name so this condition is added
+# to disable the existing test_clang_opt function for linux.
+if [[ $(uname) != "Linux" ]]; then
+    component_test_clang_opt () {
+        scripts/config.py full
+        test_build_opt 'full config' clang -O0 -Os -O2
+    }
+fi
+
+component_test_clang_latest_opt () {
     scripts/config.py full
-    test_build_opt 'full config' clang -O0 -Os -O2
+    test_build_opt 'full config' "$CLANG_LATEST" -O0 -Os -O2
+}
+support_test_clang_latest_opt () {
+    type "$CLANG_LATEST" >/dev/null 2>/dev/null
 }
 
-component_test_gcc_opt () {
+component_test_clang_earliest_opt () {
     scripts/config.py full
-    test_build_opt 'full config' gcc -O0 -Os -O2
+    test_build_opt 'full config' "$CLANG_EARLIEST" -O0
+}
+support_test_clang_earliest_opt () {
+    type "$CLANG_EARLIEST" >/dev/null 2>/dev/null
+}
+
+component_test_gcc_latest_opt () {
+    scripts/config.py full
+    test_build_opt 'full config' "$GCC_LATEST" -O0 -Os -O2
+}
+support_test_gcc_latest_opt () {
+    type "$GCC_LATEST" >/dev/null 2>/dev/null
+}
+
+component_test_gcc_earliest_opt () {
+    scripts/config.py full
+    test_build_opt 'full config' "$GCC_EARLIEST" -O0
+}
+support_test_gcc_earliest_opt () {
+    type "$GCC_EARLIEST" >/dev/null 2>/dev/null
 }
 
 component_build_mbedtls_config_file () {
diff --git a/tests/scripts/generate_test_code.py b/tests/scripts/generate_test_code.py
index ff7f9b9976..76806de95f 100755
--- a/tests/scripts/generate_test_code.py
+++ b/tests/scripts/generate_test_code.py
@@ -667,6 +667,11 @@ def parse_function_code(funcs_f, dependencies, suite_dependencies):
     code = code.replace(name, 'test_' + name, 1)
     name = 'test_' + name
 
+    # If a test function has no arguments then add 'void' argument to
+    # avoid "-Wstrict-prototypes" warnings from clang
+    if len(args) == 0:
+        code = code.replace('()', '(void)', 1)
+
     for line in funcs_f:
         if re.search(END_CASE_REGEX, line):
             break
diff --git a/tests/scripts/test_generate_test_code.py b/tests/scripts/test_generate_test_code.py
index fe748aeb46..b32d18423b 100755
--- a/tests/scripts/test_generate_test_code.py
+++ b/tests/scripts/test_generate_test_code.py
@@ -647,7 +647,7 @@ void func()
         self.assertEqual(arg, [])
         expected = '''#line 1 "test_suite_ut.function"
 
-void test_func()
+void test_func(void)
 {
     ba ba black sheep
     have you any wool
@@ -690,7 +690,7 @@ exit:
 
         expected = '''#line 1 "test_suite_ut.function"
 
-void test_func()
+void test_func(void)
 {
     ba ba black sheep
     have you any wool
@@ -750,7 +750,7 @@ exit:
 void
 
 
-test_func()
+test_func(void)
 {
     ba ba black sheep
     have you any wool
@@ -803,7 +803,7 @@ exit:
 
 
 
-void test_func()
+void test_func(void)
 {
     ba ba black sheep
     have you any wool
@@ -1139,7 +1139,7 @@ void func2()
 #if defined(MBEDTLS_ENTROPY_NV_SEED)
 #if defined(MBEDTLS_FS_IO)
 #line 13 "test_suite_ut.function"
-void test_func1()
+void test_func1(void)
 {
 exit:
     ;
@@ -1156,7 +1156,7 @@ void test_func1_wrapper( void ** params )
 #if defined(MBEDTLS_ENTROPY_NV_SEED)
 #if defined(MBEDTLS_FS_IO)
 #line 19 "test_suite_ut.function"
-void test_func2()
+void test_func2(void)
 {
 exit:
     ;