diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
index 4705c35..b97eb2e 100644
--- a/examples/CMakeLists.txt
+++ b/examples/CMakeLists.txt
@@ -4,6 +4,7 @@ target_link_libraries(tested-code xtest-assert)
 function(xtest_define_example NAME)
     set(TARGET_NAME "example-${NAME}")
     add_executable(${TARGET_NAME} ${NAME}.c ${ARGN})
+    target_compile_options(${TARGET_NAME} PRIVATE -Wall -Wextra -pedantic)
     if (NAME STREQUAL "all")
         target_compile_definitions(${TARGET_NAME} PRIVATE XTEST_ALL_EXAMPLES)
     endif ()
diff --git a/examples/all.c b/examples/all.c
index 174f4bf..3f409ac 100644
--- a/examples/all.c
+++ b/examples/all.c
@@ -1,15 +1,5 @@
 #include "xtest.h"
-
-
-void example_assertions();
-void example_expect_assertions();
-void example_fail();
-void example_float();
-void example_groups();
-void example_parameterized();
-void example_skip();
-
-
+#include "examples.h"
 
 XTEST_MAIN {
     xtest_run_group(example_assertions);
@@ -18,5 +8,6 @@ XTEST_MAIN {
     xtest_run_group(example_float);
     xtest_run_group(example_groups);
     xtest_run_group(example_parameterized);
+    xtest_run_group(example_prng);
     xtest_run_group(example_skip);
 }
diff --git a/examples/assertions.c b/examples/assertions.c
index 4c2b512..5832ba0 100644
--- a/examples/assertions.c
+++ b/examples/assertions.c
@@ -1,8 +1,8 @@
-#include <stddef.h>
 #include "xtest.h"
 #include "source.h"
+#include "examples.h"
 
-void test_assert() {
+static void test_assert() {
     int i1 = 1;
     int i2 = 1;
     int i3 = 2;
@@ -32,7 +32,7 @@ void test_assert() {
     xtest_assert(ret_1());
 }
 
-void test_assert_is() {
+static void test_assert_is() {
     int i1 = 1;
     int i2 = 1;
     int i3 = 2;
@@ -66,7 +66,7 @@ void test_assert_is() {
     xtest_assert_is_not(b1, b3);
 }
 
-void test_assert_str_is() {
+static void test_assert_str_is() {
     const char *s1 = "ret_1";
     const char *s2 = "ret_1";
     const char *s3 = "bar";
@@ -75,7 +75,7 @@ void test_assert_str_is() {
     xtest_assert_str_is_not(s1, s3);
 }
 
-void test_assert_mem_is() {
+static void test_assert_mem_is() {
     char m1[100];
     char m2[100];
     for (int i = 0; i < 100; ++i) {
@@ -91,7 +91,7 @@ void test_assert_mem_is() {
     xtest_assert_mem_is_not(m1, m2, 100);
 }
 
-void example_assertions() {
+void example_assertions(void) {
     xtest_run(test_assert);
     xtest_run(test_assert_is);
     xtest_run(test_assert_str_is);
diff --git a/examples/examples.h b/examples/examples.h
new file mode 100644
index 0000000..79e87ae
--- /dev/null
+++ b/examples/examples.h
@@ -0,0 +1,11 @@
+#ifndef XTEST_EXAMPLES_H
+#define XTEST_EXAMPLES_H
+void example_assertions(void);
+void example_expect_assertions(void);
+void example_fail(void);
+void example_float(void);
+void example_groups(void);
+void example_parameterized(void);
+void example_prng(void);
+void example_skip(void);
+#endif //XTEST_EXAMPLES_H
diff --git a/examples/expect_assertions.c b/examples/expect_assertions.c
index 3821540..a8c6e85 100644
--- a/examples/expect_assertions.c
+++ b/examples/expect_assertions.c
@@ -1,29 +1,30 @@
 #include "xtest.h"
 #include "source.h"
+#include "examples.h"
 
-void test_simple() {
+static void test_simple() {
     xtest_expect_assertion_failure();
     div(10, 0);
 }
 
-void test_no_failure() {
-    div(10,1);
+static void test_no_failure() {
+    div(10, 1);
 }
 
-void test_no_failure_2() {
-    div(10,2);
+static void test_no_failure_2() {
+    div(10, 2);
 }
 
-void test_will_fail() {
+static void test_will_fail() {
     xtest_expect_assertion_failure();
-    div(10,1);
+    div(10, 1);
 }
 
-void test_will_fail_2() {
-    div(10,0);
+static void test_will_fail_2() {
+    div(10, 0);
 }
 
-void test_other_failure() {
+static void test_other_failure() {
     xtest_expect_assertion_failure();
     xtest_assert(0);
     div(10, 0);
diff --git a/examples/fail.c b/examples/fail.c
index 6ba48ee..3e6ec7c 100644
--- a/examples/fail.c
+++ b/examples/fail.c
@@ -1,136 +1,136 @@
-#include <stddef.h>
 #include "xtest.h"
+#include "examples.h"
 
-void fail_assert() {
+static void fail_assert() {
     xtest_assert(0);
 }
 
-void fail_assert_is_char() {
-    xtest_assert_is((char)'a', (char)'b');
+static void fail_assert_is_char() {
+    xtest_assert_is((char) 'a', (char) 'b');
 }
 
-void fail_assert_is_not_char() {
-    xtest_assert_is_not((char)'a', (char)'a');
+static void fail_assert_is_not_char() {
+    xtest_assert_is_not((char) 'a', (char) 'a');
 }
 
-void fail_assert_is_signed_char() {
-    xtest_assert_is((signed char)'a', (signed char)'b');
+static void fail_assert_is_signed_char() {
+    xtest_assert_is((signed char) 'a', (signed char) 'b');
 }
 
-void fail_assert_is_not_signed_char() {
-    xtest_assert_is_not((signed char)'a', (signed char)'a');
+static void fail_assert_is_not_signed_char() {
+    xtest_assert_is_not((signed char) 'a', (signed char) 'a');
 }
 
-void fail_assert_is_unsigned_char() {
-    xtest_assert_is((unsigned char)'a', (unsigned char)'b');
+static void fail_assert_is_unsigned_char() {
+    xtest_assert_is((unsigned char) 'a', (unsigned char) 'b');
 }
 
-void fail_assert_is_not_unsigned_char() {
-    xtest_assert_is_not((unsigned char)'a', (unsigned char)'a');
+static void fail_assert_is_not_unsigned_char() {
+    xtest_assert_is_not((unsigned char) 'a', (unsigned char) 'a');
 }
 
-void fail_assert_is_short() {
+static void fail_assert_is_short() {
     xtest_assert_is((short) 1, (short) 2);
 }
 
-void fail_assert_is_not_short() {
+static void fail_assert_is_not_short() {
     xtest_assert_is_not((short) 1, (short) 1);
 }
 
-void fail_assert_is_ushort() {
+static void fail_assert_is_ushort() {
     xtest_assert_is((unsigned short) 1, (unsigned short) 2);
 }
 
-void fail_assert_is_not_ushort() {
+static void fail_assert_is_not_ushort() {
     xtest_assert_is_not((unsigned short) 1, (unsigned short) 1);
 }
 
-void fail_assert_is_int() {
+static void fail_assert_is_int() {
     xtest_assert_is((int) 1, (int) 2);
 }
 
-void fail_assert_is_not_int() {
+static void fail_assert_is_not_int() {
     xtest_assert_is_not((int) 1, (int) 1);
 }
 
-void fail_assert_is_uint() {
+static void fail_assert_is_uint() {
     xtest_assert_is((unsigned int) 1, (unsigned int) 2);
 }
 
-void fail_assert_is_not_uint() {
+static void fail_assert_is_not_uint() {
     xtest_assert_is_not((unsigned int) 1, (unsigned int) 1);
 }
 
-void fail_assert_is_long() {
+static void fail_assert_is_long() {
     xtest_assert_is((short) 1, (short) 2);
 }
 
-void fail_assert_is_not_long() {
+static void fail_assert_is_not_long() {
     xtest_assert_is_not((long) 1, (long) 1);
 }
 
-void fail_assert_is_ulong() {
+static void fail_assert_is_ulong() {
     xtest_assert_is((unsigned long) 1, (unsigned long) 2);
 }
 
-void fail_assert_is_not_ulong() {
+static void fail_assert_is_not_ulong() {
     xtest_assert_is_not((unsigned long) 1, (unsigned long) 1);
 }
 
-void fail_assert_is_longlong() {
+static void fail_assert_is_longlong() {
     xtest_assert_is((long long) 1, (long long) 2);
 }
 
-void fail_assert_is_not_longlong() {
+static void fail_assert_is_not_longlong() {
     xtest_assert_is_not((long long) 1, (long long) 1);
 }
 
-void fail_assert_is_ulonglong() {
+static void fail_assert_is_ulonglong() {
     xtest_assert_is((unsigned long long) 1, (unsigned long long) 2);
 }
 
-void fail_assert_is_not_ulonglong() {
+static void fail_assert_is_not_ulonglong() {
     xtest_assert_is_not((unsigned long long) 1, (unsigned long long) 1);
 }
 
-void fail_assert_is_ptr() {
+static void fail_assert_is_ptr() {
     int i = 1;
     int j = 1;
-    xtest_assert_is((void*) &i, (void*) &j);
+    xtest_assert_is((void *) &i, (void *) &j);
 }
 
-void fail_assert_is_not_ptr() {
+static void fail_assert_is_not_ptr() {
     int i = 1;
-    xtest_assert_is_not((void*) &i, (void*) &i);
+    xtest_assert_is_not((void *) &i, (void *) &i);
 }
 
-void fail_assert_str_is() {
+static void fail_assert_str_is() {
     xtest_assert_str_is("foo", "bar");
 }
 
-void fail_assert_str_is_not() {
+static void fail_assert_str_is_not() {
     xtest_assert_str_is_not("foo", "foo");
 }
 
-void fail_assert_mem_is() {
+static void fail_assert_mem_is() {
     xtest_assert_mem_is("aaaaaaaaaaaaa", "aaaaaaaaaaaab", 13);
 }
 
-void fail_assert_mem_is_not() {
+static void fail_assert_mem_is_not() {
     xtest_assert_mem_is_not("aaaaaaaaaaaaa", "aaaaaaaaaaaab", 12);
 }
 
 
-void fail_assert_float_is() {
+static void fail_assert_float_is() {
     xtest_assert_float_is(1.2356, 1.2346, 3);
 }
 
 
-void fail_assert_float_is_not() {
+static void fail_assert_float_is_not() {
     xtest_assert_float_is_not(1.2356, 1.2346, 2);
 }
 
-void fail_assert_is() {
+static void fail_assert_is(void) {
     xtest_run(fail_assert_is_char);
     xtest_run(fail_assert_is_not_char);
     xtest_run(fail_assert_is_signed_char);
@@ -157,22 +157,22 @@ void fail_assert_is() {
     xtest_run(fail_assert_is_not_ptr);
 }
 
-void fail_assert_str() {
+static void fail_assert_str(void) {
     xtest_run(fail_assert_str_is);
     xtest_run(fail_assert_str_is_not);
 }
 
-void fail_assert_mem() {
+static void fail_assert_mem(void) {
     xtest_run(fail_assert_mem_is);
     xtest_run(fail_assert_mem_is_not);
 }
 
-void fail_assert_float() {
+static void fail_assert_float(void) {
     xtest_run(fail_assert_float_is);
     xtest_run(fail_assert_float_is_not);
 }
 
-void example_fail() {
+void example_fail(void) {
     xtest_run(fail_assert);
     xtest_run_group(fail_assert_is);
     xtest_run_group(fail_assert_str);
diff --git a/examples/float.c b/examples/float.c
index f23fde1..ac231d3 100644
--- a/examples/float.c
+++ b/examples/float.c
@@ -1,5 +1,5 @@
-#include <stddef.h>
 #include "xtest.h"
+#include "examples.h"
 
 void test_float() {
     xtest_assert_float_is(1.0, 1.0, 0);
@@ -34,7 +34,7 @@ void test_float() {
     xtest_assert_float_is_not(0.001, 0.00100000000001, 16);
 }
 
-void example_float() {
+void example_float(void) {
     xtest_run(test_float);
 }
 
diff --git a/examples/groups.c b/examples/groups.c
index 45af64e..e8c5407 100644
--- a/examples/groups.c
+++ b/examples/groups.c
@@ -1,18 +1,26 @@
-#include <stddef.h>
 #include "xtest.h"
+#include "examples.h"
 
-void test_1() {}
-void test_2() {}
-void test_3() {}
-void test_4() {}
-void test_5() {}
-void test_6() {}
-void test_7() {}
-void test_8() {}
-void test_9() {}
+static void test_1() {}
+
+static void test_2() {}
+
+static void test_3() {}
+
+static void test_4() {}
+
+static void test_5() {}
+
+static void test_6() {}
+
+static void test_7() {}
+
+static void test_8() {}
+
+static void test_9() {}
 
 
-void groups_manual() {
+static void groups_manual(void) {
     xtest_group(A);
     xtest_group(foo);
     xtest_run(test_1);
@@ -42,55 +50,55 @@ void groups_manual() {
     xtest_end_group();
 }
 
-void bar() {
+static void bar(void) {
     xtest_run(test_2);
     xtest_run(test_3);
 }
 
-void foo() {
+static void foo(void) {
     xtest_run(test_1);
     xtest_run_group(bar);
 }
 
-void A() {
+static void A(void) {
     xtest_run_group(foo);
     xtest_run(test_4);
 }
 
-void B() {
+static void B(void) {
     xtest_run(test_5);
     xtest_run(test_6);
 }
 
-void Z() {
+static void Z(void) {
     xtest_run(test_7);
 }
 
-void Y() {
+static void Y(void) {
     xtest_run_group(Z);
 }
 
-void X() {
+static void X(void) {
     xtest_run_group(Y);
 }
 
-void C() {
+static void C(void) {
     xtest_run_group(X);
 }
 
-void D() {
+static void D(void) {
     xtest_run(test_8);
     xtest_run(test_9);
 }
 
-void groups_convenient() {
+static void groups_convenient(void) {
     xtest_run_group(A);
     xtest_run_group(B);
     xtest_run_group(C);
     xtest_run_group(D);
 }
 
-void example_groups() {
+void example_groups(void) {
     groups_manual();
     groups_convenient();
 }
diff --git a/examples/parameterized.c b/examples/parameterized.c
index 6f7e17b..d6fb220 100644
--- a/examples/parameterized.c
+++ b/examples/parameterized.c
@@ -1,6 +1,6 @@
-#include <stddef.h>
 #include "xtest.h"
 #include "source.h"
+#include "examples.h"
 
 void test_add(XTEST_UNUSED void *fixture, void **params) {
     int a = xtest_get_param(int, 0, params);
@@ -20,7 +20,6 @@ void test_str_equals(XTEST_UNUSED void *fixture, void **params) {
 }
 
 
-
 xtest_param add_params[] = {
     {
         .name = "A",
@@ -73,7 +72,7 @@ xtest_param str_params[] = {
     }
 };
 
-void example_parameterized() {
+void example_parameterized(void) {
     xtest_run_parameterized(test_add, add_params);
     xtest_run_parameterized(test_str_equals, str_params);
 }
diff --git a/examples/prng.c b/examples/prng.c
index 9a7fb4c..a8732ce 100644
--- a/examples/prng.c
+++ b/examples/prng.c
@@ -1,5 +1,6 @@
 #include "xtest.h"
 #include "source.h"
+#include "examples.h"
 
 
 void rand_int() {
@@ -9,9 +10,19 @@ void rand_int() {
     xtest_assert_is(add(a, b), res);
 }
 
+void rand_double() {
+    double a = xtest_rand_double_range(0, 10);
+    double b = xtest_rand_double_range(0, 10);
+    double diff = a - b;
+    xtest_assert(diff < 10.0);
+}
+
+void example_prng(void) {
+    xtest_run(rand_int);
+    xtest_run(rand_double);
+}
+
 
 #ifndef XTEST_ALL_EXAMPLES
-XTEST_MAIN {
-    xtest_run(rand_int);
-}
+XTEST_RUN_MAIN(example_prng)
 #endif
diff --git a/examples/skip.c b/examples/skip.c
index 2f6849d..4834d33 100644
--- a/examples/skip.c
+++ b/examples/skip.c
@@ -1,5 +1,6 @@
 #include "xtest.h"
 #include "source.h"
+#include "examples.h"
 
 void no_skip_1() {}
 
@@ -37,7 +38,7 @@ void skip_6() {
     xtest_skip(NULL);
 }
 
-void example_skip() {
+void example_skip(void) {
     xtest_run(no_skip_1);
     xtest_run(skip_1);
     xtest_run(no_skip_2);
diff --git a/examples/source.c b/examples/source.c
index 36801d0..35c7214 100644
--- a/examples/source.c
+++ b/examples/source.c
@@ -2,13 +2,13 @@
 #include "source.h"
 #include "assert.h"
 
-int ret_1() {
+int ret_1(void) {
     return 1;
 }
 
 double div(double a, double b) {
     assert(b != 0.0);
-    return a/b;
+    return a / b;
 }
 
 
diff --git a/examples/source.h b/examples/source.h
index 2c23264..c16b3a9 100644
--- a/examples/source.h
+++ b/examples/source.h
@@ -1,13 +1,13 @@
 #ifndef XTEST_SOURCE_H
 #define XTEST_SOURCE_H
 
-int ret_1();
+int ret_1(void);
 
 double div(double a, double b);
 
 
 int add(int a, int b);
 
-int str_equals(const char * s1, const char * s2);
+int str_equals(const char *s1, const char *s2);
 
 #endif //XTEST_SOURCE_H
diff --git a/include/xtest-assert/assert.h b/include/xtest-assert/assert.h
index f694dad..668e971 100644
--- a/include/xtest-assert/assert.h
+++ b/include/xtest-assert/assert.h
@@ -1,5 +1,7 @@
 #if defined(__GNUC__) || defined(__clang__) || defined(XTEST_USE_INCLUDE_NEXT)
+
 #include_next <assert.h>
+
 #else
 #include <assert.h>
 #endif
@@ -9,11 +11,11 @@
 
 #if defined(XTEST) && !defined(XTEST_XTEST_H)
 
-void xtest_internal_assert(const char* file, int line, const char* func, const char* expr);
+void xtest_internal_assert(const char *file, int line, const char *func, const char *expr);
 
 #undef assert
 
 #define assert(__e) ((__e) ? (void)0 : xtest_internal_assert(__FILE__, __LINE__, \
-						       __func__, #__e))
+                               __func__, #__e))
 
 #endif //defined(XTEST) && !defined(XTEST_XTEST_H)
diff --git a/include/xtest/xtest.h b/include/xtest/xtest.h
index c3952a2..916fb72 100644
--- a/include/xtest/xtest.h
+++ b/include/xtest/xtest.h
@@ -15,9 +15,9 @@
 #include <string.h>
 #include <stdint.h>
 
-typedef void (*xtest_test_fn)(void * fixture, void ** params);
-typedef void (*xtest_setup_fn)(void ** fixture);
-typedef void (*xtest_teardown_fn)(void * fixture);
+typedef void (*xtest_test_fn)(void *fixture, void **params);
+typedef void (*xtest_setup_fn)(void **fixture);
+typedef void (*xtest_teardown_fn)(void *fixture);
 
 typedef struct xtest_param_s xtest_param;
 
@@ -48,37 +48,39 @@ enum xtest_type {
     xtest_type_other,
 };
 
-void xtest_init(int argc, char**argv);
+void xtest_init(int argc, char **argv);
 
 void xtest_fail_assert(const char *expression, const char *file, int line, void *expected,
                        void *actual, _Bool invert, enum xtest_type type);
 void
-xtest_assert_float(double expected, double actual, int precision, _Bool invert, const char *expression, const char *file,
+xtest_assert_float(double expected, double actual, int precision, _Bool invert, const char *expression,
+                   const char *file,
                    int line);
 
-void xtest_assert_mem(const char *expected, const char *actual, size_t length, _Bool invert, const char *expression, const char *file,
+void xtest_assert_mem(const char *expected, const char *actual, size_t length, _Bool invert, const char *expression,
+                      const char *file,
                       int line);
 
 void xtest_internal_run(xtest_test_fn fn, const char *name, xtest_param *params, xtest_setup_fn setup,
                         xtest_teardown_fn teardown);
 
 void xtest_internal_start_group(const char *name);
-void xtest_internal_end_group();
+void xtest_internal_end_group(void);
 
 void xtest_skip(const char *reason);
-void xtest_expect_assertion_failure();
-int xtest_complete();
+void xtest_expect_assertion_failure(void);
+int xtest_complete(void);
 
 #ifdef XTEST_PRNG
-void xtest_rand_fill(char* buf, size_t len);
-double xtest_rand_double();
+void xtest_rand_fill(char *buf, size_t len);
+double xtest_rand_double(void);
 double xtest_rand_double_range(double min, double max);
-int xtest_rand_int();
+int xtest_rand_int(void);
 int xtest_rand_int_range(int min, int max);
-uint8_t xtest_rand_8();
-uint16_t xtest_rand_16();
-uint32_t xtest_rand_32();
-uint64_t xtest_rand_64();
+uint8_t xtest_rand_8(void);
+uint16_t xtest_rand_16(void);
+uint32_t xtest_rand_32(void);
+uint64_t xtest_rand_64(void);
 #endif
 
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 1390711..58188d3 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,18 +1,18 @@
 
 set(XTEST_LINK_LIBRARIES "")
 
-if(XTEST_ENABLE_PRNG)
+if (XTEST_ENABLE_PRNG)
     add_library(pcg ${XTEST_SOURCE_DIR}/extern/pcg/pcg_basic.c)
     set(XTEST_LINK_LIBRARIES ${XTEST_LINK_LIBRARIES} pcg)
     set(XTEST_ADDITIONAL_DEFINES XTEST_PRNG)
     find_library(MATH_LIBRARY m)
-    if(MATH_LIBRARY)
+    if (MATH_LIBRARY)
         set(XTEST_LINK_LIBRARIES ${XTEST_LINK_LIBRARIES} ${MATH_LIBRARY})
-    endif()
-endif()
+    endif ()
+endif ()
 
 add_library(xtest xtest.c)
-target_compile_options(xtest PRIVATE -Wall -Wextra -pedantic)
+target_compile_options(xtest PRIVATE -Wall -Wextra -pedantic -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition -Wold-style-declaration)
 target_include_directories(xtest PRIVATE ${XTEST_SOURCE_DIR}/extern/pcg)
 target_link_libraries(xtest PRIVATE ${XTEST_LINK_LIBRARIES})
 target_compile_definitions(xtest PUBLIC XTEST ${XTEST_ADDITIONAL_DEFINES})
diff --git a/src/xtest.c b/src/xtest.c
index eb4a114..bb748d8 100644
--- a/src/xtest.c
+++ b/src/xtest.c
@@ -76,6 +76,9 @@ int skipped_tests = 0;
 _Bool list_tests = 0;
 
 
+void xtest_internal_assert(const char *file, int line, const char *func, const char *expr);
+
+
 #define USAGE_BASE "[-?|--help] [-l|--list] [-m|--match filter] [-f|--output-format format]"
 #define USAGE_PRNG "[-s|--seed prng-seed]"
 
@@ -206,7 +209,7 @@ void xtest_init(int argc, char **argv) {
 }
 
 
-int xtest_complete() {
+int xtest_complete(void) {
     if (!list_tests) {
         if (output_format == format_default) {
             printf("============\nTotal: %d, Failed: %d, Skipped: %d\n", num_tests, failed_tests, skipped_tests);
@@ -218,7 +221,7 @@ int xtest_complete() {
     }
 }
 
-void subunit_message(const char *name, const char *message, const char *details) {
+static void subunit_message(const char *name, const char *message, const char *details) {
     printf("%s: %s", message, name);
     if (details == NULL) {
         printf("\n");
@@ -467,7 +470,7 @@ xtest_assert_float(double expected, double actual, int precision, _Bool invert,
     longjmp(xtest_jmp, 1);
 }
 
-size_t find_diff_offset(const char *a, const char *b, size_t length) {
+static size_t find_diff_offset(const char *a, const char *b, size_t length) {
     size_t offset = 0;
     while (offset < length && *(a + offset) == *(b + offset)) offset++;
     return offset;
@@ -510,13 +513,13 @@ void xtest_internal_start_group(const char *name) {
     xtest_indent += XTEST_INDENT;
 }
 
-void xtest_internal_end_group() {
+void xtest_internal_end_group(void) {
     assert(group_nesting_pos > 0);
     group_nesting_pos -= 1;
     xtest_indent -= XTEST_INDENT;
 }
 
-void xtest_expect_assertion_failure() {
+void xtest_expect_assertion_failure(void) {
     expecting_assertion = 1;
 }
 
@@ -537,7 +540,7 @@ union seed_encode_box {
     uint8_t bytes[PRNG_SEED_LENGTH * 6 / 8 + 1];
 };
 
-void encode_seed(prng_seed seed, uint64_t state, uint64_t seq) {
+static void encode_seed(prng_seed seed, uint64_t state, uint64_t seq) {
     union seed_encode_box box;
     memset(&box, 0, sizeof(box));
     box.state = state;
@@ -571,7 +574,7 @@ void encode_seed(prng_seed seed, uint64_t state, uint64_t seq) {
     seed[PRNG_SEED_LENGTH] = '\0';
 }
 
-void decode_seed(const prng_seed seed, uint64_t *state, uint64_t *seq) {
+static void decode_seed(const prng_seed seed, uint64_t *state, uint64_t *seq) {
     union seed_encode_box box;
     memset(&box, 0, sizeof(box));
     uint8_t cur;
@@ -638,7 +641,7 @@ void xtest_rand_fill(char *buf, size_t len) {
     }
 }
 
-double xtest_rand_double() {
+double xtest_rand_double(void) {
     return ldexp((double) (xtest_rand_64() & 0xFFFFFFFFFFFFF), -52);
 }
 
@@ -647,7 +650,7 @@ double xtest_rand_double_range(double min, double max) {
     return (max - min) * xtest_rand_double() + min;
 }
 
-int xtest_rand_int() {
+int xtest_rand_int(void) {
     uint32_t uval = pcg32_random_r(&rng);
     int32_t *ival;
     ival = (int32_t *) &uval;
@@ -662,20 +665,20 @@ int xtest_rand_int_range(int min, int max) {
     return (int) *ival + min;
 }
 
-uint8_t xtest_rand_8() {
+uint8_t xtest_rand_8(void) {
     return (uint8_t) pcg32_random_r(&rng);
 }
 
-uint16_t xtest_rand_16() {
+uint16_t xtest_rand_16(void) {
     return (uint16_t) pcg32_random_r(&rng);
 }
 
-uint32_t xtest_rand_32() {
+uint32_t xtest_rand_32(void) {
     return pcg32_random_r(&rng);
 
 }
 
-uint64_t xtest_rand_64() {
+uint64_t xtest_rand_64(void) {
     uint32_t l = pcg32_random_r(&rng);
     uint32_t h = pcg32_random_r(&rng);
     return ((uint64_t) h) << 32 | l;