diff --git a/TSRM/threads.m4 b/TSRM/threads.m4
index dc5719bbec056..c42b328dd6651 100644
--- a/TSRM/threads.m4
+++ b/TSRM/threads.m4
@@ -73,7 +73,7 @@ void *thread_routine(void *data) {
     return data;
 }
 
-int main() {
+int main(void) {
     pthread_t thd;
     pthread_mutexattr_t mattr;
     int data = 1;
diff --git a/Zend/Zend.m4 b/Zend/Zend.m4
index 06b19c85c712b..e7a6603ddbf07 100644
--- a/Zend/Zend.m4
+++ b/Zend/Zend.m4
@@ -220,7 +220,7 @@ typedef union _mm_align_test {
 #define ZEND_MM_ALIGNMENT (sizeof(mm_align_test))
 #endif
 
-int main()
+int main(void)
 {
   size_t i = ZEND_MM_ALIGNMENT;
   int zeros = 0;
diff --git a/build/libtool.m4 b/build/libtool.m4
index 8ee7b453010f1..5b518d50e4ef5 100644
--- a/build/libtool.m4
+++ b/build/libtool.m4
@@ -277,7 +277,7 @@ dnl This sometimes fails to find confdefs.h, for some reason.
 dnl [#]line __oline__ "[$]0"
 [#]line __oline__ "configure"
 #include "confdefs.h"
-int main() {
+int main(void) {
 ; return 0; }
 EOF
 if AC_TRY_EVAL(ac_link) && test -s conftest${ac_exeext}; then
@@ -978,8 +978,8 @@ else
 #  endif
 #endif
 
-void fnord() { int i=42;}
-int main ()
+void fnord(void) { int i=42;}
+int main (void)
 {
   void *self = dlopen (0, LT_DLGLOBAL|LT_DLLAZY_OR_NOW);
   int status = $lt_dlunknown;
@@ -2750,7 +2750,7 @@ _LT_AC_TAGVAR(objext, $1)=$objext
 lt_simple_compile_test_code="int some_variable = 0;"
 
 # Code to be used in simple link tests
-lt_simple_link_test_code='int main(){return(0);}'
+lt_simple_link_test_code='int main(void){return(0);}'
 
 _LT_AC_SYS_COMPILER
 
@@ -4640,7 +4640,7 @@ void nm_test_func(){}
 #ifdef __cplusplus
 }
 #endif
-int main(){nm_test_var='a';nm_test_func();return(0);}
+int main(void){nm_test_var='a';nm_test_func();return(0);}
 EOF
 
   if AC_TRY_EVAL(ac_compile); then
diff --git a/build/ltmain.sh b/build/ltmain.sh
index 2f1c8c9dc80f0..ff1685c8a89f9 100755
--- a/build/ltmain.sh
+++ b/build/ltmain.sh
@@ -3598,7 +3598,7 @@ EOF
 	  # whether they linked in statically or dynamically with ldd.
 	  $rm conftest.c
 	  cat > conftest.c <<EOF
-	  int main() { return 0; }
+	  int main(void) { return 0; }
 EOF
 	  $rm conftest
 	  if $LTCC $LTCFLAGS -o conftest conftest.c $deplibs; then
diff --git a/build/php.m4 b/build/php.m4
index 6ebc54b1b466d..2bc0733a978a6 100644
--- a/build/php.m4
+++ b/build/php.m4
@@ -1034,7 +1034,7 @@ AC_DEFUN([_PHP_CHECK_SIZEOF], [
 #endif
 $3
 
-int main()
+int main(void)
 {
 	FILE *fp = fopen("conftestval", "w");
 	if (!fp) return(1);
@@ -1102,7 +1102,7 @@ AC_CACHE_CHECK(for type of reentrant time-related functions, ac_cv_time_r_type,[
 AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <time.h>
 
-int main() {
+int main(void) {
 char buf[27];
 struct tm t;
 time_t old = 0;
@@ -1118,7 +1118,7 @@ return (1);
 ],[
   AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <time.h>
-int main() {
+int main(void) {
   struct tm t, *s;
   time_t old = 0;
   char buf[27], *p;
@@ -1159,7 +1159,7 @@ AC_DEFUN([PHP_DOES_PWRITE_WORK],[
 #include <errno.h>
 #include <stdlib.h>
 $1
-    int main() {
+    int main(void) {
     int fd = open("conftest_in", O_WRONLY|O_CREAT, 0600);
 
     if (fd < 0) return 1;
@@ -1193,7 +1193,7 @@ AC_DEFUN([PHP_DOES_PREAD_WORK],[
 #include <errno.h>
 #include <stdlib.h>
 $1
-    int main() {
+    int main(void) {
     char buf[3];
     int fd = open("conftest_in", O_RDONLY);
     if (fd < 0) return 1;
@@ -1261,27 +1261,27 @@ dnl PHP_MISSING_TIME_R_DECL
 dnl
 AC_DEFUN([PHP_MISSING_TIME_R_DECL],[
   AC_MSG_CHECKING([for missing declarations of reentrant functions])
-  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <time.h>]], [[struct tm *(*func)() = localtime_r]])],[
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <time.h>]], [[struct tm *(*func)(void) = localtime_r]])],[
     :
   ],[
     AC_DEFINE(MISSING_LOCALTIME_R_DECL,1,[Whether localtime_r is declared])
   ])
-  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <time.h>]], [[struct tm *(*func)() = gmtime_r]])],[
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <time.h>]], [[struct tm *(*func)(void) = gmtime_r]])],[
     :
   ],[
     AC_DEFINE(MISSING_GMTIME_R_DECL,1,[Whether gmtime_r is declared])
   ])
-  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <time.h>]], [[char *(*func)() = asctime_r]])],[
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <time.h>]], [[char *(*func)(void) = asctime_r]])],[
     :
   ],[
     AC_DEFINE(MISSING_ASCTIME_R_DECL,1,[Whether asctime_r is declared])
   ])
-  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <time.h>]], [[char *(*func)() = ctime_r]])],[
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <time.h>]], [[char *(*func)(void) = ctime_r]])],[
     :
   ],[
     AC_DEFINE(MISSING_CTIME_R_DECL,1,[Whether ctime_r is declared])
   ])
-  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <string.h>]], [[char *(*func)() = strtok_r]])],[
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <string.h>]], [[char *(*func)(void) = strtok_r]])],[
     :
   ],[
     AC_DEFINE(MISSING_STRTOK_R_DECL,1,[Whether strtok_r is declared])
@@ -1315,7 +1315,7 @@ dnl See if we have broken header files like SunOS has.
 dnl
 AC_DEFUN([PHP_MISSING_FCLOSE_DECL],[
   AC_MSG_CHECKING([for fclose declaration])
-  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stdio.h>]], [[int (*func)() = fclose]])],[
+  AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stdio.h>]], [[int (*func)(void) = fclose]])],[
     AC_DEFINE(MISSING_FCLOSE_DECL,0,[ ])
     AC_MSG_RESULT([ok])
   ],[
@@ -1405,7 +1405,7 @@ struct s
   int i;
   char c[1];
 };
-int main()
+int main(void)
 {
   struct s *s = malloc(sizeof(struct s) + 3);
   s->i = 3;
@@ -1463,7 +1463,7 @@ int seeker(void *cookie, off64_t *position, int whence)
 
 cookie_io_functions_t funcs = {reader, writer, seeker, closer};
 
-int main() {
+int main(void) {
   struct cookiedata g = { 0 };
   FILE *fp = fopencookie(&g, "r", funcs);
 
@@ -1590,7 +1590,7 @@ AC_DEFUN([PHP_CHECK_FUNC_LIB],[
   if test "$found" = "yes"; then
     ac_libs=$LIBS
     LIBS="$LIBS -l$2"
-    AC_RUN_IFELSE([AC_LANG_SOURCE([[int main() { return (0); }]])],[found=yes],[found=no],[
+    AC_RUN_IFELSE([AC_LANG_PROGRAM()],[found=yes],[found=no],[
       dnl Cross compilation.
       found=yes
     ])
@@ -1643,8 +1643,8 @@ AC_DEFUN([PHP_TEST_BUILD], [
   LIBS="$4 $LIBS"
   AC_LINK_IFELSE([AC_LANG_SOURCE([[
     $5
-    char $1();
-    int main() {
+    char $1(void);
+    int main(void) {
       $1();
       return 0;
     }
@@ -2296,7 +2296,7 @@ AC_DEFUN([PHP_TEST_WRITE_STDOUT],[
 
 #define TEXT "This is the test message -- "
 
-int main()
+int main(void)
 {
   int n;
 
diff --git a/configure.ac b/configure.ac
index 701e6d5b966a2..de0eac8498ec8 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1120,7 +1120,7 @@ case $host_alias in
     save_LDFLAGS=$LDFLAGS
     LDFLAGS="$LDFLAGS -Wl,-zcommon-page-size=2097152 -Wl,-zmax-page-size=2097152"
     AC_RUN_IFELSE(
-        [AC_LANG_SOURCE([[int main() {return 0;}]])],
+        [AC_LANG_PROGRAM()],
         [ac_cv_common_page_size=yes],
         [ac_cv_common_page_size=no],
         [ac_cv_common_page_size=no])
@@ -1134,7 +1134,7 @@ case $host_alias in
         save_LDFLAGS=$LDFLAGS
         LDFLAGS="$LDFLAGS -Wl,-zmax-page-size=2097152"
         AC_RUN_IFELSE(
-            [AC_LANG_SOURCE([[int main() {return 0;}]])],
+            [AC_LANG_PROGRAM()],
             [ac_cv_max_page_size=yes],
             [ac_cv_max_page_size=no],
             [ac_cv_max_page_size=no])
diff --git a/ext/gd/config.m4 b/ext/gd/config.m4
index 9bdd6bb11c04d..a8b1c76d2d131 100644
--- a/ext/gd/config.m4
+++ b/ext/gd/config.m4
@@ -239,7 +239,7 @@ dnl Various checks for GD features
 
     PHP_TEST_BUILD(foobar, [], [
       AC_MSG_ERROR([GD build test failed. Please check the config.log for details.])
-    ], [ $GD_SHARED_LIBADD ], [char foobar () {}])
+    ], [ $GD_SHARED_LIBADD ], [char foobar (void) {}])
 
   else
     extra_sources="gd_compat.c"
diff --git a/ext/iconv/config.m4 b/ext/iconv/config.m4
index ac57c81e7d472..5d408de8331d9 100644
--- a/ext/iconv/config.m4
+++ b/ext/iconv/config.m4
@@ -30,7 +30,7 @@ if test "$PHP_ICONV" != "no"; then
       AC_MSG_CHECKING([if using GNU libiconv])
       AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #include <iconv.h>
-int main() {
+int main(void) {
   printf("%d", _libiconv_version);
   return 0;
 }
@@ -90,7 +90,7 @@ int main() {
 #include <iconv.h>
 #include <errno.h>
 
-int main() {
+int main(void) {
   iconv_t cd;
   cd = iconv_open( "*blahblah*", "*blahblahblah*" );
   if (cd == (iconv_t)(-1)) {
@@ -117,7 +117,7 @@ int main() {
 #include <iconv.h>
 #include <stdlib.h>
 
-int main() {
+int main(void) {
   iconv_t cd = iconv_open( "UTF-8//IGNORE", "UTF-8" );
   if(cd == (iconv_t)-1) {
     return 1;
diff --git a/ext/opcache/config.m4 b/ext/opcache/config.m4
index d35efbc689ed9..6bf07ad35e2e0 100644
--- a/ext/opcache/config.m4
+++ b/ext/opcache/config.m4
@@ -121,7 +121,7 @@ if test "$PHP_OPCACHE" != "no"; then
 #include <unistd.h>
 #include <string.h>
 
-int main() {
+int main(void) {
   pid_t pid;
   int status;
   int ipc_id;
@@ -200,7 +200,7 @@ int main() {
 # define MAP_FAILED ((void*)-1)
 #endif
 
-int main() {
+int main(void) {
   pid_t pid;
   int status;
   char *shm;
@@ -262,7 +262,7 @@ int main() {
 # define MAP_FAILED ((void*)-1)
 #endif
 
-int main() {
+int main(void) {
   pid_t pid;
   int status;
   int fd;
diff --git a/ext/standard/config.m4 b/ext/standard/config.m4
index 8e77e75134c9e..1f25edb9ee058 100644
--- a/ext/standard/config.m4
+++ b/ext/standard/config.m4
@@ -81,7 +81,7 @@ if test "$PHP_EXTERNAL_LIBCRYPT" != "no"; then
 #include <stdlib.h>
 #include <string.h>
 
-int main() {
+int main(void) {
 #if HAVE_CRYPT
 	char *encrypted = crypt("rasmuslerdorf","rl");
 	return !encrypted || strcmp(encrypted,"rl.3StKT.4T8M");
@@ -111,7 +111,7 @@ int main() {
 #include <stdlib.h>
 #include <string.h>
 
-int main() {
+int main(void) {
 #if HAVE_CRYPT
 	char *encrypted = crypt("rasmuslerdorf","_J9..rasm");
 	return !encrypted || strcmp(encrypted,"_J9..rasmBYk8r9AiWNc");
@@ -141,7 +141,7 @@ int main() {
 #include <stdlib.h>
 #include <string.h>
 
-int main() {
+int main(void) {
 #if HAVE_CRYPT
 	char salt[15], answer[40];
 	char *encrypted;
@@ -181,7 +181,7 @@ int main() {
 #include <stdlib.h>
 #include <string.h>
 
-int main() {
+int main(void) {
 #if HAVE_CRYPT
 	char salt[30], answer[70];
 	char *encrypted;
@@ -218,7 +218,7 @@ int main() {
 #include <stdlib.h>
 #include <string.h>
 
-int main() {
+int main(void) {
 #if HAVE_CRYPT
 	char salt[21], answer[21+86];
 	char *encrypted;
@@ -254,7 +254,7 @@ int main() {
 #include <stdlib.h>
 #include <string.h>
 
-int main() {
+int main(void) {
 #if HAVE_CRYPT
 	char salt[21], answer[21+43];
 	char *encrypted;
diff --git a/sapi/fpm/config.m4 b/sapi/fpm/config.m4
index aa2a85d2ca632..e3d52084c8204 100644
--- a/sapi/fpm/config.m4
+++ b/sapi/fpm/config.m4
@@ -90,7 +90,7 @@ AC_DEFUN([AC_FPM_CLOCK],
       #include <mach/clock.h>
       #include <mach/mach_error.h>
 
-      int main()
+      int main(void)
       {
         kern_return_t ret; clock_serv_t aClock; mach_timespec_t aTime;
         ret = host_get_clock_service(mach_host_self(), REALTIME_CLOCK, &aClock);
@@ -158,7 +158,7 @@ AC_DEFUN([AC_FPM_TRACE],
       #define PTRACE_PEEKDATA PT_READ_D
       #endif
 
-      int main()
+      int main(void)
       {
         long v1 = (unsigned int) -1; /* copy will fail if sizeof(long) == 8 and we've got "int ptrace()" */
         long v2;
@@ -263,7 +263,7 @@ AC_DEFUN([AC_FPM_TRACE],
       #include <sys/stat.h>
       #include <fcntl.h>
       #include <stdio.h>
-      int main()
+      int main(void)
       {
         long v1 = (unsigned int) -1, v2 = 0;
         char buf[128];
@@ -604,7 +604,7 @@ if test "$PHP_FPM" != "no"; then
     AC_CHECK_HEADERS([sys/acl.h])
 
     AC_COMPILE_IFELSE([AC_LANG_SOURCE([[#include <sys/acl.h>
-      int main()
+      int main(void)
       {
         acl_t acl;
         acl_entry_t user, group;
@@ -623,7 +623,7 @@ if test "$PHP_FPM" != "no"; then
           AC_MSG_RESULT([yes])
         ],[
           AC_RUN_IFELSE([AC_LANG_SOURCE([[#include <sys/acl.h>
-            int main()
+            int main(void)
             {
               acl_t acl;
               acl_entry_t user, group;