diff --git a/Makefile b/Makefile
index 473192c..5f33e25 100644
--- a/Makefile
+++ b/Makefile
@@ -6,13 +6,13 @@ TARGET = vip
 PREFIX ?= /usr/local
 BINDIR = $(PREFIX)/bin
 
-CFLAGS = -O3 -march=native -mtune=native -pipe -s -flto -std=c99 -pedantic -Wall
+CFLAGS = -Os -march=native -mtune=native -pipe -s -flto -std=c99 -pedantic -Wall -D_DEFAULT_SOURCE
 
 SRC != find src -name *.c
 INCLUDE = include
 
 $(TARGET): $(SRC) config.h
-	$(CC) $(SRC) config.h -o $@ $(CFLAGS) -I$(INCLUDE) -I.
+	$(CC) $(SRC) -o $@ $(CFLAGS) -I$(INCLUDE) -I.
 
 dist:
 	mkdir -p $(TARGET)-$(VERSION)
diff --git a/include/editor.h b/include/editor.h
index b68215c..60e861d 100644
--- a/include/editor.h
+++ b/include/editor.h
@@ -1,16 +1,16 @@
 #ifndef EDITOR_H_
 #define EDITOR_H_
 
-void refresh_screen();
+void refresh_screen(void);
 void move_cursor(int key);
-void scroll();
+void scroll(void);
 void insert_char(int c);
-void insert_new_line();
-void shift_new_line();
-void del_char();
-void init_editor();
+void insert_new_line(void);
+void shift_new_line(void);
+void del_char(void);
+void init_editor(void);
 void open_editor(char *filename);
 char *prompt_editor(char *prompt, void (*callback)(char *, int));
-void find_editor();
+void find_editor(void);
 
 #endif
diff --git a/include/io.h b/include/io.h
index 6899136..15d0c31 100644
--- a/include/io.h
+++ b/include/io.h
@@ -1,9 +1,9 @@
 #ifndef IO_H_
 #define IO_H_
 
-int read_key();
-void save_file();
-void process_key();
+int read_key(void);
+void save_file(void);
+void process_key(void);
 void draw_rows(struct abuf *ab);
 
 #endif
diff --git a/include/syntax.h b/include/syntax.h
index 9e42d04..db6026f 100644
--- a/include/syntax.h
+++ b/include/syntax.h
@@ -21,6 +21,6 @@ typedef struct language {
 int is_separator(int c);
 void update_highlight(row *row);
 char *syntax_to_color(int hl, size_t *len);
-void select_syntax_highlight();
+void select_syntax_highlight(void);
 
 #endif
diff --git a/include/term.h b/include/term.h
index 9affe20..c4ea7d7 100644
--- a/include/term.h
+++ b/include/term.h
@@ -4,8 +4,8 @@
 #define CTRL_KEY(k) ((k) & 0x1f)
 
 void die(const char *s);
-void reset_term();
-void setup_term();
+void reset_term(void);
+void setup_term(void);
 int get_cursor_position(int *rows, int *cols);
 int get_window_size(int *rows, int *cols);
 
diff --git a/src/editor.c b/src/editor.c
index 2350b51..dab4672 100644
--- a/src/editor.c
+++ b/src/editor.c
@@ -12,7 +12,7 @@
 
 extern editor vip;
 
-void refresh_screen()
+void refresh_screen(void)
 {
 	scroll();
 
@@ -68,7 +68,7 @@ void move_cursor(int key)
 	}
 }
 
-void scroll()
+void scroll(void)
 {
 	vip.rx = 0;
 	if (vip.cy < vip.rows) {
@@ -97,7 +97,7 @@ void insert_char(int c)
 	vip.cx++;
 }
 
-void insert_new_line()
+void insert_new_line(void)
 {
 	if (vip.cx == 0) {
 		insert_row(vip.cy, "", 0);
@@ -116,14 +116,14 @@ void insert_new_line()
 /*
  * 'o' in vim
  */
-void shift_new_line()
+void shift_new_line(void)
 {
 	insert_row(vip.cy + 1, "", 0);
 	vip.cy++;
 	vip.cx = 0;
 }
 
-void del_char()
+void del_char(void)
 {
 	if (vip.cy == vip.rows) return;
 	if (vip.cx == 0 && vip.cy == 0) return;
@@ -140,7 +140,7 @@ void del_char()
 	}
 }
 
-void init_editor()
+void init_editor(void)
 {
 	vip.cx = 0;
 	vip.cy = 0;
@@ -280,7 +280,7 @@ void find_callback(char *query, int key)
 	}
 }
 
-void find_editor()
+void find_editor(void)
 {
 	int tmp_cx = vip.cx;
 	int tmp_cy = vip.cy;
diff --git a/src/io.c b/src/io.c
index c9b337d..ee65050 100644
--- a/src/io.c
+++ b/src/io.c
@@ -10,7 +10,7 @@
 #include "vip.h"
 #include "bar.h"
 
-int read_key()
+int read_key(void)
 {
 	int nread;
 	char c;
@@ -65,7 +65,7 @@ int read_key()
 	}
 }
 
-void save_file()
+void save_file(void)
 {
 	if (vip.filename == NULL) {
 		vip.filename = prompt_editor("Save as: %s", NULL);
@@ -94,7 +94,7 @@ void save_file()
 	set_status_bar_message("Error saving: %s", strerror(errno));
 }
 
-void process_key()
+void process_key(void)
 {
 	int c = read_key();
 	switch (c) {
diff --git a/src/syntax.c b/src/syntax.c
index 02cb594..642ea21 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -185,7 +185,7 @@ char *syntax_to_color(int hl, size_t *len)
 	}
 }
 
-void select_syntax_highlight()
+void select_syntax_highlight(void)
 {
 	vip.syntax = NULL;
 	if (vip.filename == NULL) return;
diff --git a/src/term.c b/src/term.c
index 94f7869..48f8e30 100644
--- a/src/term.c
+++ b/src/term.c
@@ -15,7 +15,7 @@ void die(const char *s)
 	exit(1);
 }
 
-void reset_term()
+void reset_term(void)
 {
 	if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &vip.termios) == -1) {
 		die("tcsetattr");
@@ -26,7 +26,7 @@ void reset_term()
 /*
  * Setup terminal
  */
-void setup_term()
+void setup_term(void)
 {
 	write(STDOUT_FILENO, "\x1b[?1049h\x1b[2J", 12);
 	if (tcgetattr(STDIN_FILENO, &vip.termios) == -1) {