diff --git a/Zend/Zend.m4 b/Zend/Zend.m4
index bbfc3985a7b61..ca6768d2d6c54 100644
--- a/Zend/Zend.m4
+++ b/Zend/Zend.m4
@@ -214,6 +214,7 @@ AX_CHECK_COMPILE_FLAG([-Wimplicit-fallthrough=1], CFLAGS="$CFLAGS -Wimplicit-fal
 AX_CHECK_COMPILE_FLAG([-Wduplicated-cond], CFLAGS="-Wduplicated-cond $CFLAGS", , [-Werror])
 AX_CHECK_COMPILE_FLAG([-Wlogical-op], CFLAGS="-Wlogical-op $CFLAGS", , [-Werror])
 AX_CHECK_COMPILE_FLAG([-Wformat-truncation], CFLAGS="-Wformat-truncation $CFLAGS", , [-Werror])
+AX_CHECK_COMPILE_FLAG([-Wstrict-prototypes], CFLAGS="-Wstrict-prototypes $CFLAGS", , [-Werror])
 AX_CHECK_COMPILE_FLAG([-fno-common], CFLAGS="-fno-common $CFLAGS", , [-Werror])
 
 test -n "$DEBUG_CFLAGS" && CFLAGS="$CFLAGS $DEBUG_CFLAGS"
diff --git a/azure/macos/job.yml b/azure/macos/job.yml
index ed2e8d9d223e1..59ca396de7714 100644
--- a/azure/macos/job.yml
+++ b/azure/macos/job.yml
@@ -65,7 +65,6 @@ jobs:
             --with-mhash \
             --with-sodium \
             --enable-dba \
-            --enable-werror \
             --with-config-file-path=/etc \
             --with-config-file-scan-dir=/etc/php.d
       displayName: 'Configure Build'
diff --git a/ext/gd/config.m4 b/ext/gd/config.m4
index 28390770376e2..03c61032aa2d0 100644
--- a/ext/gd/config.m4
+++ b/ext/gd/config.m4
@@ -138,7 +138,8 @@ dnl
 if test "$PHP_GD" != "no"; then
 
   if test "$PHP_EXTERNAL_GD" = "no"; then
-    GD_CFLAGS=""
+    dnl Disable strict prototypes as GD takes advantages of variadic function signatures for function pointers.
+    GD_CFLAGS="-Wno-strict-prototypes"
     extra_sources="libgd/gd.c libgd/gd_gd.c libgd/gd_gd2.c libgd/gd_io.c libgd/gd_io_dp.c \
                   libgd/gd_io_file.c libgd/gd_ss.c libgd/gd_io_ss.c libgd/gd_webp.c \
                   libgd/gd_png.c libgd/gd_jpeg.c libgd/gdxpm.c libgd/gdfontt.c libgd/gdfonts.c \
diff --git a/ext/intl/collator/collator_is_numeric.c b/ext/intl/collator/collator_is_numeric.c
index 3cda24291b990..823fb4088d8fd 100644
--- a/ext/intl/collator/collator_is_numeric.c
+++ b/ext/intl/collator/collator_is_numeric.c
@@ -110,16 +110,13 @@ static double collator_u_strtod(const UChar *nptr, UChar **endptr) /* {{{ */
  *
  * Ignores `locale' stuff.
  */
-static zend_long collator_u_strtol(nptr, endptr, base)
-	const UChar *nptr;
-	UChar **endptr;
-	register int base;
+static zend_long collator_u_strtol(const UChar *nptr, UChar **endptr, int base)
 {
-	register const UChar *s = nptr;
-	register zend_ulong acc;
-	register UChar c;
-	register zend_ulong cutoff;
-	register int neg = 0, any, cutlim;
+	const UChar *s = nptr;
+	zend_ulong acc;
+	UChar c;
+	zend_ulong cutoff;
+	int neg = 0, any, cutlim;
 
 	if (s == NULL) {
 		errno = ERANGE;
diff --git a/ext/pcntl/pcntl.c b/ext/pcntl/pcntl.c
index 1e8690ae75144..e51074deace93 100644
--- a/ext/pcntl/pcntl.c
+++ b/ext/pcntl/pcntl.c
@@ -89,7 +89,8 @@ static void pcntl_siginfo_to_zval(int, siginfo_t*, zval*);
 #else
 static void pcntl_signal_handler(int);
 #endif
-static void pcntl_signal_dispatch();
+static void pcntl_signal_dispatch(void);
+static void pcntl_signal_dispatch_tick_function(int dummy_int, void *dummy_pointer);
 static void pcntl_interrupt_function(zend_execute_data *execute_data);
 
 void php_register_signal_constants(INIT_FUNC_ARGS)
@@ -424,7 +425,7 @@ static PHP_GINIT_FUNCTION(pcntl)
 
 PHP_RINIT_FUNCTION(pcntl)
 {
-	php_add_tick_function(pcntl_signal_dispatch, NULL);
+	php_add_tick_function(pcntl_signal_dispatch_tick_function, NULL);
 	zend_hash_init(&PCNTL_G(php_signal_table), 16, NULL, ZVAL_PTR_DTOR, 0);
 	PCNTL_G(head) = PCNTL_G(tail) = PCNTL_G(spares) = NULL;
 	PCNTL_G(async_signals) = 0;
@@ -1385,6 +1386,11 @@ void pcntl_signal_dispatch()
 	sigprocmask(SIG_SETMASK, &old_mask, NULL);
 }
 
+static void pcntl_signal_dispatch_tick_function(int dummy_int, ZEND_ATTRIBUTE_UNUSED void *dummy_pointer)
+{
+	return pcntl_signal_dispatch();
+}
+
 /* {{{ Enable/disable asynchronous signal handling and return the old setting. */
 PHP_FUNCTION(pcntl_async_signals)
 {
diff --git a/ext/pspell/config.m4 b/ext/pspell/config.m4
index a0212165f6e8f..db49b4fd86bb9 100644
--- a/ext/pspell/config.m4
+++ b/ext/pspell/config.m4
@@ -4,7 +4,8 @@ PHP_ARG_WITH([pspell],
     [Include PSPELL support. GNU Aspell version 0.50.0 or higher required])])
 
 if test "$PHP_PSPELL" != "no"; then
-	PHP_NEW_EXTENSION(pspell, pspell.c, $ext_shared)
+	dnl Add -Wno-strict-prototypes as depends on user libs
+	PHP_NEW_EXTENSION(pspell, pspell.c, $ext_shared, , "-Wno-strict-prototypes")
 	if test "$PHP_PSPELL" != "yes"; then
 	    PSPELL_SEARCH_DIRS=$PHP_PSPELL
 	else
diff --git a/ext/readline/config.m4 b/ext/readline/config.m4
index ed205764f2b35..209f92b6e0a76 100644
--- a/ext/readline/config.m4
+++ b/ext/readline/config.m4
@@ -137,6 +137,7 @@ elif test "$PHP_LIBEDIT" != "no"; then
 fi
 
 if test "$PHP_READLINE" != "no" || test "$PHP_LIBEDIT" != "no"; then
-  PHP_NEW_EXTENSION(readline, readline.c readline_cli.c, $ext_shared, cli)
+  dnl Add -Wno-strict-prototypes as depends on user libs
+  PHP_NEW_EXTENSION(readline, readline.c readline_cli.c, $ext_shared, cli, "-Wno-strict-prototypes")
   PHP_SUBST(READLINE_SHARED_LIBADD)
 fi
diff --git a/ext/readline/readline_cli.c b/ext/readline/readline_cli.c
index d6116711276d4..7a0fe78595e5b 100644
--- a/ext/readline/readline_cli.c
+++ b/ext/readline/readline_cli.c
@@ -743,7 +743,7 @@ this extension sharedto offer compatibility.
 #define GET_SHELL_CB(cb) \
 	do { \
 		(cb) = NULL; \
-		cli_shell_callbacks_t *(*get_callbacks)(); \
+		cli_shell_callbacks_t *(*get_callbacks)(void); \
 		get_callbacks = dlsym(RTLD_DEFAULT, "php_cli_get_shell_callbacks"); \
 		if (get_callbacks) { \
 			(cb) = get_callbacks(); \
diff --git a/ext/standard/scanf.c b/ext/standard/scanf.c
index f58b4195cc599..78ecc1642cf92 100644
--- a/ext/standard/scanf.c
+++ b/ext/standard/scanf.c
@@ -106,6 +106,8 @@ typedef struct CharSet {
 	} *ranges;
 } CharSet;
 
+typedef zend_long (*int_string_formater)(const char*, char**, int);
+
 /*
  * Declarations for functions used only in this file.
  */
@@ -583,7 +585,7 @@ PHPAPI int php_sscanf_internal( char *string, char *format,
 	int  base = 0;
 	int  underflow = 0;
 	size_t width;
-	zend_long (*fn)() = NULL;
+	int_string_formater fn = NULL;
 	char *ch, sch;
 	int  flags;
 	char buf[64];	/* Temporary buffer to hold scanned number
@@ -740,29 +742,29 @@ PHPAPI int php_sscanf_internal( char *string, char *format,
 			case 'D':
 				op = 'i';
 				base = 10;
-				fn = (zend_long (*)())ZEND_STRTOL_PTR;
+				fn = (int_string_formater)ZEND_STRTOL_PTR;
 				break;
 			case 'i':
 				op = 'i';
 				base = 0;
-				fn = (zend_long (*)())ZEND_STRTOL_PTR;
+				fn = (int_string_formater)ZEND_STRTOL_PTR;
 				break;
 			case 'o':
 				op = 'i';
 				base = 8;
-				fn = (zend_long (*)())ZEND_STRTOL_PTR;
+				fn = (int_string_formater)ZEND_STRTOL_PTR;
 				break;
 			case 'x':
 			case 'X':
 				op = 'i';
 				base = 16;
-				fn = (zend_long (*)())ZEND_STRTOL_PTR;
+				fn = (int_string_formater)ZEND_STRTOL_PTR;
 				break;
 			case 'u':
 				op = 'i';
 				base = 10;
 				flags |= SCAN_UNSIGNED;
-				fn = (zend_long (*)())ZEND_STRTOUL_PTR;
+				fn = (int_string_formater)ZEND_STRTOUL_PTR;
 				break;
 
 			case 'f':
diff --git a/sapi/fpm/fpm/events/kqueue.c b/sapi/fpm/fpm/events/kqueue.c
index 746f2fa1e1b04..5c7b388e78ea9 100644
--- a/sapi/fpm/fpm/events/kqueue.c
+++ b/sapi/fpm/fpm/events/kqueue.c
@@ -28,7 +28,7 @@
 #include <errno.h>
 
 static int fpm_event_kqueue_init(int max);
-static int fpm_event_kqueue_clean();
+static int fpm_event_kqueue_clean(void);
 static int fpm_event_kqueue_wait(struct fpm_event_queue_s *queue, unsigned long int timeout);
 static int fpm_event_kqueue_add(struct fpm_event_s *ev);
 static int fpm_event_kqueue_remove(struct fpm_event_s *ev);