diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1561ca270..9fab172a5 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -293,7 +293,7 @@ if(CYGWIN)
   # We build SDL on cygwin without the UNIX emulation layer
   target_include_directories(sdl-build-options INTERFACE "/usr/include/mingw")
   set(CMAKE_REQUIRED_FLAGS "${CMAKE_REQUIRED_FLAGS} -mno-cygwin")
-  check_c_source_compiles("int main(int argc, char **argv) {}"
+  check_c_source_compiles("int main(int argc, char **argv) { return 0; }"
     HAVE_GCC_NO_CYGWIN)
   set(CMAKE_REQUIRED_FLAGS ${ORIG_CMAKE_REQUIRED_FLAGS})
   if(HAVE_GCC_NO_CYGWIN)
@@ -545,7 +545,7 @@ if(USE_GCC OR USE_CLANG)
         #if !defined(__GNUC__) || __GNUC__ < 3
         #error Dependency tracking requires GCC 3.0 or newer
         #endif
-        int main(int argc, char **argv) { }" HAVE_DEPENDENCY_TRACKING)
+        int main(int argc, char **argv) { return 0; }" HAVE_DEPENDENCY_TRACKING)
   endif()
 
   if(SDL_GCC_ATOMICS)
@@ -556,17 +556,19 @@ if(USE_GCC OR USE_CLANG)
         __sync_lock_test_and_set(&x, y);
         __sync_fetch_and_add(&a, 1);
         __sync_bool_compare_and_swap(&a, 5, 10);
-        __sync_bool_compare_and_swap(&x, y, z); }" HAVE_GCC_ATOMICS)
+        __sync_bool_compare_and_swap(&x, y, z);
+        return 0; }" HAVE_GCC_ATOMICS)
     if(NOT HAVE_GCC_ATOMICS)
       check_c_source_compiles("int main(int argc, char **argv) {
           int a;
           __sync_lock_test_and_set(&a, 1);
-          __sync_lock_release(&a); }" HAVE_GCC_SYNC_LOCK_TEST_AND_SET)
+          __sync_lock_release(&a);
+          return 0; }" HAVE_GCC_SYNC_LOCK_TEST_AND_SET)
     endif()
   endif()
 
   set(CMAKE_REQUIRED_FLAGS "-mpreferred-stack-boundary=2")
-  check_c_source_compiles("int x = 0; int main(int argc, char **argv) {}"
+  check_c_source_compiles("int x = 0; int main(int argc, char **argv) { return 0; }"
     HAVE_GCC_PREFERRED_STACK_BOUNDARY)
   set(CMAKE_REQUIRED_FLAGS ${ORIG_CMAKE_REQUIRED_FLAGS})
 
@@ -575,7 +577,7 @@ if(USE_GCC OR USE_CLANG)
       #if !defined(__GNUC__) || __GNUC__ < 4
       #error SDL only uses visibility attributes in GCC 4 or newer
       #endif
-      int main(int argc, char **argv) {}" HAVE_GCC_FVISIBILITY)
+      int main(int argc, char **argv) { return 0; }" HAVE_GCC_FVISIBILITY)
   if(HAVE_GCC_FVISIBILITY)
     list(APPEND EXTRA_CFLAGS "-fvisibility=hidden")
   endif()
@@ -631,7 +633,7 @@ if(SDL_ASSEMBLY)
           #ifndef __MMX__
           #error Assembler CPP flag not enabled
           #endif
-          int main(int argc, char **argv) { }" HAVE_MMX)
+          int main(int argc, char **argv) { return 0; }" HAVE_MMX)
       if(HAVE_MMX)
         list(APPEND EXTRA_CFLAGS "-mmmx")
       endif()
@@ -648,6 +650,7 @@ if(SDL_ASSEMBLY)
           int main(int argc, char **argv) {
             void *p = 0;
             _m_prefetch(p);
+            return 0;
           }" HAVE_3DNOW)
       if(HAVE_3DNOW)
         list(APPEND EXTRA_CFLAGS "-m3dnow")
@@ -671,7 +674,7 @@ if(SDL_ASSEMBLY)
           #ifndef __SSE__
           #error Assembler CPP flag not enabled
           #endif
-          int main(int argc, char **argv) { }" HAVE_SSE)
+          int main(int argc, char **argv) { return 0; }" HAVE_SSE)
       if(HAVE_SSE)
         list(APPEND EXTRA_CFLAGS "-msse")
       endif()
@@ -694,7 +697,7 @@ if(SDL_ASSEMBLY)
           #ifndef __SSE2__
           #error Assembler CPP flag not enabled
           #endif
-          int main(int argc, char **argv) { }" HAVE_SSE2)
+          int main(int argc, char **argv) { return 0; }" HAVE_SSE2)
       if(HAVE_SSE2)
         list(APPEND EXTRA_CFLAGS "-msse2")
       endif()
@@ -717,7 +720,7 @@ if(SDL_ASSEMBLY)
           #ifndef __SSE3__
           #error Assembler CPP flag not enabled
           #endif
-          int main(int argc, char **argv) { }" HAVE_SSE3)
+          int main(int argc, char **argv) { return 0; }" HAVE_SSE3)
       if(HAVE_SSE3)
         list(APPEND EXTRA_CFLAGS "-msse3")
       endif()
@@ -746,12 +749,12 @@ if(SDL_ASSEMBLY)
           vector unsigned int vzero() {
               return vec_splat_u32(0);
           }
-          int main(int argc, char **argv) { }" HAVE_ALTIVEC_H_HDR)
+          int main(int argc, char **argv) { return 0; }" HAVE_ALTIVEC_H_HDR)
       check_c_source_compiles("
           vector unsigned int vzero() {
               return vec_splat_u32(0);
           }
-          int main(int argc, char **argv) { }" HAVE_ALTIVEC)
+          int main(int argc, char **argv) { return 0; }" HAVE_ALTIVEC)
       set(CMAKE_REQUIRED_FLAGS ${ORIG_CMAKE_REQUIRED_FLAGS})
       if(HAVE_ALTIVEC OR HAVE_ALTIVEC_H_HDR)
         set(HAVE_ALTIVEC TRUE) # if only HAVE_ALTIVEC_H_HDR is set
@@ -878,7 +881,7 @@ if(SDL_LIBC)
     # TODO: refine the mprotect check
     check_c_source_compiles("#include <sys/types.h>
                              #include <sys/mman.h>
-                             int main() { }" HAVE_MPROTECT)
+                             int main() { return 0; }" HAVE_MPROTECT)
     foreach(_FN
             strtod malloc calloc realloc free getenv setenv putenv unsetenv
             qsort abs bcopy memset memcpy memmove memcmp strlen strlcpy strlcat
@@ -1156,9 +1159,7 @@ if(ANDROID)
       #if defined(__ARM_ARCH) && __ARM_ARCH < 7
       #error Vulkan doesn't work on this configuration
       #endif
-      int main(void) {
-          return 0;
-      }
+      int main(int argc, char **argv) { return 0; }
       " VULKAN_PASSED_ANDROID_CHECKS)
       if(VULKAN_PASSED_ANDROID_CHECKS)
         set(SDL_VIDEO_VULKAN 1)
@@ -1294,7 +1295,7 @@ elseif(UNIX AND NOT APPLE AND NOT ANDROID AND NOT RISCOS AND NOT HAIKU)
         #ifndef EVIOCGNAME
         #error EVIOCGNAME() ioctl not available
         #endif
-        int main(int argc, char** argv) {}" HAVE_INPUT_EVENTS)
+        int main(int argc, char** argv) { return 0; }" HAVE_INPUT_EVENTS)
 
     if(LINUX)
       check_c_source_compiles("
@@ -1306,6 +1307,7 @@ elseif(UNIX AND NOT APPLE AND NOT ANDROID AND NOT RISCOS AND NOT HAIKU)
               struct kbentry kbe;
               kbe.kb_table = KG_CTRL;
               ioctl(0, KDGKBENT, &kbe);
+              return 0;
           }" HAVE_INPUT_KD)
     elseif(FREEBSD)
       check_c_source_compiles("
@@ -1316,6 +1318,7 @@ elseif(UNIX AND NOT APPLE AND NOT ANDROID AND NOT RISCOS AND NOT HAIKU)
           {
               accentmap_t accTable;
               ioctl(0, KDENABIO, 1);
+              return 0;
           }" HAVE_INPUT_KBIO)
     endif()
 
@@ -1515,7 +1518,7 @@ elseif(WINDOWS)
 
   check_c_source_compiles("
     #include <windows.h>
-    int main(int argc, char **argv) { }" HAVE_WIN32_CC)
+    int main(int argc, char **argv) { return 0; }" HAVE_WIN32_CC)
 
   file(GLOB CORE_SOURCES ${SDL2_SOURCE_DIR}/src/core/windows/*.c)
   set(SOURCE_FILES ${SOURCE_FILES} ${CORE_SOURCES})
@@ -1580,22 +1583,22 @@ elseif(WINDOWS)
     check_c_source_compiles("
       #include <windows.h>
       #include <xinput.h>
-      int main(int argc, char **argv) { }" HAVE_XINPUT_H)
+      int main(int argc, char **argv) { return 0; }" HAVE_XINPUT_H)
     check_c_source_compiles("
       #include <windows.h>
       #include <xinput.h>
       XINPUT_GAMEPAD_EX x1;
-      int main(int argc, char **argv) { }" HAVE_XINPUT_GAMEPAD_EX)
+      int main(int argc, char **argv) { return 0; }" HAVE_XINPUT_GAMEPAD_EX)
     check_c_source_compiles("
       #include <windows.h>
       #include <xinput.h>
       XINPUT_STATE_EX s1;
-      int main(int argc, char **argv) { }" HAVE_XINPUT_STATE_EX)
+      int main(int argc, char **argv) { return 0; }" HAVE_XINPUT_STATE_EX)
     check_c_source_compiles("
       #define COBJMACROS
       #include <windows.gaming.input.h>
       __x_ABI_CWindows_CGaming_CInput_CIGamepadStatics2 *s2;
-      int main(int argc, char **argv) { }" HAVE_WINDOWS_GAMING_INPUT_H)
+      int main(int argc, char **argv) { return 0; }" HAVE_WINDOWS_GAMING_INPUT_H)
   endif()
 
   # headers needed elsewhere
@@ -1897,13 +1900,13 @@ elseif(APPLE)
           #if TARGET_CPU_X86
           #error GameController framework doesn't work on this configuration
           #endif
-          int main() {}" HAVE_FRAMEWORK_GAMECONTROLLER)
+          int main() { return 0; }" HAVE_FRAMEWORK_GAMECONTROLLER)
       check_objc_source_compiles("
           #include <AvailabilityMacros.h>
           #include <TargetConditionals.h>
           #import <Foundation/Foundation.h>
           #import <CoreHaptics/CoreHaptics.h>
-          int main() {}" HAVE_FRAMEWORK_COREHAPTICS)
+          int main() { return 0; }" HAVE_FRAMEWORK_COREHAPTICS)
       if(HAVE_FRAMEWORK_GAMECONTROLLER AND HAVE_FRAMEWORK_COREHAPTICS)
         # Only enable MFI if we also have CoreHaptics to ensure rumble works
         set(SDL_JOYSTICK_MFI 1)
@@ -2020,7 +2023,7 @@ elseif(APPLE)
         #if (!TARGET_CPU_X86_64 && !TARGET_CPU_ARM64)
         #error Metal doesn't work on this configuration
         #endif
-        int main(void) {}" HAVE_FRAMEWORK_METAL)
+        int main(int argc, char **argv) { return 0; }" HAVE_FRAMEWORK_METAL)
       if(HAVE_FRAMEWORK_METAL)
         set(SDL_FRAMEWORK_METAL 1)
         set(SDL_FRAMEWORK_QUARTZCORE 1)
diff --git a/cmake/sdlchecks.cmake b/cmake/sdlchecks.cmake
index 697274c95..7385761ea 100644
--- a/cmake/sdlchecks.cmake
+++ b/cmake/sdlchecks.cmake
@@ -48,6 +48,7 @@ macro(CheckDLOPEN)
        int main(int argc, char **argv) {
          void *handle = dlopen(\"\", RTLD_NOW);
          const char *loaderror = (char *) dlerror();
+         return 0;
        }" HAVE_DLOPEN)
     set(CMAKE_REQUIRED_LIBRARIES)
   endif()
@@ -57,8 +58,7 @@ macro(CheckO_CLOEXEC)
   check_c_source_compiles("
     #include <fcntl.h>
     int flag = O_CLOEXEC;
-    int main(void) {
-   }" HAVE_O_CLOEXEC)
+    int main(int argc, char **argv) { return 0; }" HAVE_O_CLOEXEC)
 endmacro()
 
 # Requires:
@@ -68,12 +68,12 @@ macro(CheckOSS)
     set(OSS_HEADER_FILE "sys/soundcard.h")
     check_c_source_compiles("
         #include <sys/soundcard.h>
-        int main() { int arg = SNDCTL_DSP_SETFRAGMENT; }" OSS_FOUND)
+        int main(int argc, char **argv) { int arg = SNDCTL_DSP_SETFRAGMENT; return 0; }" OSS_FOUND)
     if(NOT OSS_FOUND)
       set(OSS_HEADER_FILE "soundcard.h")
       check_c_source_compiles("
           #include <soundcard.h>
-          int main() { int arg = SNDCTL_DSP_SETFRAGMENT; }" OSS_FOUND)
+          int main(int argc, char **argv) { int arg = SNDCTL_DSP_SETFRAGMENT; return 0; }" OSS_FOUND)
     endif()
 
     if(OSS_FOUND)
@@ -481,7 +481,8 @@ macro(CheckX11)
             XGenericEventCookie *cookie = &event.xcookie;
             XNextEvent(display, &event);
             XGetEventData(display, cookie);
-            XFreeEventData(display, cookie); }" HAVE_XGENERICEVENT)
+            XFreeEventData(display, cookie);
+            return 0; }" HAVE_XGENERICEVENT)
       if(HAVE_XGENERICEVENT)
         set(SDL_VIDEO_DRIVER_X11_SUPPORTS_GENERIC_EVENTS 1)
       endif()
@@ -533,7 +534,7 @@ macro(CheckX11)
             {
               return (Status)0;
             }
-            int main(int argc, char **argv) {}" HAVE_XINPUT2_MULTITOUCH)
+            int main(int argc, char **argv) { return 0; }" HAVE_XINPUT2_MULTITOUCH)
         if(HAVE_XINPUT2_MULTITOUCH)
           set(SDL_VIDEO_DRIVER_X11_XINPUT2_SUPPORTS_MULTITOUCH 1)
         endif()
@@ -547,7 +548,7 @@ macro(CheckX11)
             #include <X11/extensions/XInput2.h>
             #include <X11/extensions/Xfixes.h>
             BarrierEventID b;
-            int main(void) { }" HAVE_XFIXES_H)
+            int main(int argc, char **argv) { return 0; }" HAVE_XFIXES_H)
       endif()
       if(SDL_X11_XFIXES AND HAVE_XFIXES_H AND HAVE_XINPUT2_H)
         if(HAVE_X11_SHARED AND XFIXES_LIB)
@@ -777,12 +778,12 @@ macro(CheckVivante)
   if(SDL_VIVANTE)
     check_c_source_compiles("
         #include <gc_vdk.h>
-        int main(int argc, char** argv) {}" HAVE_VIVANTE_VDK)
+        int main(int argc, char** argv) { return 0; }" HAVE_VIVANTE_VDK)
     check_c_source_compiles("
         #define LINUX
         #define EGL_API_FB
         #include <EGL/eglvivante.h>
-        int main(int argc, char** argv) {}" HAVE_VIVANTE_EGL_FB)
+        int main(int argc, char** argv) { return 0; }" HAVE_VIVANTE_EGL_FB)
     if(HAVE_VIVANTE_VDK OR HAVE_VIVANTE_EGL_FB)
       set(HAVE_VIVANTE TRUE)
       set(HAVE_SDL_VIDEO TRUE)
@@ -807,7 +808,7 @@ macro(CheckGLX)
   if(SDL_OPENGL)
     check_c_source_compiles("
         #include <GL/glx.h>
-        int main(int argc, char** argv) {}" HAVE_OPENGL_GLX)
+        int main(int argc, char** argv) { return 0; }" HAVE_OPENGL_GLX)
     if(HAVE_OPENGL_GLX)
       set(SDL_VIDEO_OPENGL_GLX 1)
     endif()
@@ -826,7 +827,7 @@ macro(CheckEGL)
         #define EGL_NO_X11
         #include <EGL/egl.h>
         #include <EGL/eglext.h>
-        int main (int argc, char** argv) {}" HAVE_OPENGL_EGL)
+        int main (int argc, char** argv) { return 0; }" HAVE_OPENGL_EGL)
     if(HAVE_OPENGL_EGL)
       set(SDL_VIDEO_OPENGL_EGL 1)
     endif()
@@ -840,7 +841,7 @@ macro(CheckOpenGL)
     check_c_source_compiles("
         #include <GL/gl.h>
         #include <GL/glext.h>
-        int main(int argc, char** argv) {}" HAVE_OPENGL)
+        int main(int argc, char** argv) { return 0; }" HAVE_OPENGL)
     if(HAVE_OPENGL)
       set(SDL_VIDEO_OPENGL 1)
       set(SDL_VIDEO_RENDER_OGL 1)
@@ -855,7 +856,7 @@ macro(CheckOpenGLES)
     check_c_source_compiles("
         #include <GLES/gl.h>
         #include <GLES/glext.h>
-        int main (int argc, char** argv) {}" HAVE_OPENGLES_V1)
+        int main (int argc, char** argv) { return 0; }" HAVE_OPENGLES_V1)
     if(HAVE_OPENGLES_V1)
         set(HAVE_OPENGLES TRUE)
         set(SDL_VIDEO_OPENGL_ES 1)
@@ -864,7 +865,7 @@ macro(CheckOpenGLES)
     check_c_source_compiles("
         #include <GLES2/gl2.h>
         #include <GLES2/gl2ext.h>
-        int main (int argc, char** argv) {}" HAVE_OPENGLES_V2)
+        int main (int argc, char** argv) { return 0; }" HAVE_OPENGLES_V2)
     if(HAVE_OPENGLES_V2)
         set(HAVE_OPENGLES TRUE)
         set(SDL_VIDEO_OPENGL_ES2 1)