diff --git a/.travis.yml b/.travis.yml
index 87c996fb..8098035c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -35,7 +35,7 @@ install:
 script:
   - docker run -v $PWD:/usr/src/i3/ -w /usr/src/i3 ${BASENAME} ./travis/check-safe-wrappers.sh
   - docker run -v $PWD:/usr/src/i3/ -w /usr/src/i3 ${BASENAME} ./travis/check-formatting.sh
-  - docker run -v $PWD:/usr/src/i3/ -w /usr/src/i3 -e CC ${BASENAME} /bin/sh -c 'autoreconf -fi && mkdir -p build && cd build && (../configure || (cat config.log; false)) && make -j CFLAGS="-Wformat -Wformat-security -Wextra -Wno-unused-parameter -Werror"'
+  - docker run -v $PWD:/usr/src/i3/ -w /usr/src/i3 -e CC ${BASENAME} /bin/sh -c 'autoreconf -fi && mkdir -p build && cd build && (../configure || (cat config.log; false)) && make -j CFLAGS="-Wformat -Wformat-security -Wextra -Wno-unused-parameter -Wstrict-prototypes -Wmissing-prototypes -Werror"'
   - docker run -v $PWD:/usr/src/i3/ -w /usr/src/i3 ${BASENAME} ./travis/check-spelling.pl
   - docker run -v $PWD:/usr/src/i3/ -w /usr/src/i3 -e CC ${BASENAME} ./travis/run-tests.sh
   - ./travis/skip-pkg.sh || docker run -v $PWD:/usr/src/i3/ -w /usr/src/i3 ${BASENAME} ./travis/debian-build.sh deb/debian-amd64/DIST
diff --git a/i3-config-wizard/main.c b/i3-config-wizard/main.c
index 0c8c705a..4b556657 100644
--- a/i3-config-wizard/main.c
+++ b/i3-config-wizard/main.c
@@ -104,7 +104,7 @@ static struct xkb_keymap *xkb_keymap;
 static uint8_t xkb_base_event;
 static uint8_t xkb_base_error;
 
-static void finish();
+static void finish(void);
 
 #include "GENERATED_config_enums.h"
 
@@ -216,7 +216,7 @@ static const char *get_string(const char *identifier) {
 
 static void clear_stack(void) {
     for (int c = 0; c < 10; c++) {
-        if (stack[c].type == STACK_STR && stack[c].val.str != NULL)
+        if (stack[c].type == STACK_STR)
             free(stack[c].val.str);
         stack[c].identifier = NULL;
         stack[c].val.str = NULL;
@@ -482,7 +482,7 @@ static void txt(int col, int row, char *text, color_t fg, color_t bg) {
  * Handles expose events, that is, draws the window contents.
  *
  */
-static int handle_expose() {
+static int handle_expose(void) {
     const color_t black = draw_util_hex_to_color("#000000");
     const color_t white = draw_util_hex_to_color("#FFFFFF");
     const color_t green = draw_util_hex_to_color("#00FF00");
@@ -641,7 +641,7 @@ static void handle_button_press(xcb_button_press_event_t *event) {
  * Creates the config file and tells i3 to reload.
  *
  */
-static void finish() {
+static void finish(void) {
     printf("creating \"%s\"...\n", config_path);
 
     struct xkb_context *xkb_context;
diff --git a/i3-input/main.c b/i3-input/main.c
index efb7b20c..d1a2efd7 100644
--- a/i3-input/main.c
+++ b/i3-input/main.c
@@ -156,7 +156,7 @@ static int handle_key_release(void *ignored, xcb_connection_t *conn, xcb_key_rel
     return 1;
 }
 
-static void finish_input() {
+static void finish_input(void) {
     char *command = (char *)concat_strings(glyphs_utf8, input_position);
 
     /* count the occurrences of %s in the string */
diff --git a/i3-nagbar/main.c b/i3-nagbar/main.c
index fd7acd6e..4ce74939 100644
--- a/i3-nagbar/main.c
+++ b/i3-nagbar/main.c
@@ -103,10 +103,10 @@ void debuglog(char *fmt, ...) {
 }
 
 /*
- * Starts the given application by passing it through a shell. We use double fork
- * to avoid zombie processes. As the started application’s parent exits (immediately),
- * the application is reparented to init (process-id 1), which correctly handles
- * childs, so we don’t have to do it :-).
+ * Starts the given application by passing it through a shell. We use double
+ * fork to avoid zombie processes. As the started application’s parent exits
+ * (immediately), the application is reparented to init (process-id 1), which
+ * correctly handles children, so we don’t have to do it :-).
  *
  * The shell is determined by looking for the SHELL environment variable. If it
  * does not exist, /bin/sh is used.
diff --git a/i3bar/include/xcb.h b/i3bar/include/xcb.h
index 7783e877..760ebcdb 100644
--- a/i3bar/include/xcb.h
+++ b/i3bar/include/xcb.h
@@ -60,7 +60,7 @@ int separator_symbol_width;
  * depend on 'config'.
  *
  */
-char *init_xcb_early();
+char *init_xcb_early(void);
 
 /**
  * Initialization which depends on 'config' being usable. Called after the
diff --git a/i3bar/src/child.c b/i3bar/src/child.c
index 1cd7d512..bb5ceaff 100644
--- a/i3bar/src/child.c
+++ b/i3bar/src/child.c
@@ -133,7 +133,7 @@ finish:
  * Stop and free() the stdin- and SIGCHLD-watchers
  *
  */
-void cleanup(void) {
+static void cleanup(void) {
     if (stdin_io != NULL) {
         ev_io_stop(main_loop, stdin_io);
         FREE(stdin_io);
@@ -400,7 +400,7 @@ static bool read_json_input(unsigned char *input, int length) {
  * in statusline
  *
  */
-void stdin_io_cb(struct ev_loop *loop, ev_io *watcher, int revents) {
+static void stdin_io_cb(struct ev_loop *loop, ev_io *watcher, int revents) {
     int rec;
     unsigned char *buffer = get_buffer(watcher, &rec);
     if (buffer == NULL)
@@ -420,7 +420,7 @@ void stdin_io_cb(struct ev_loop *loop, ev_io *watcher, int revents) {
  * whether this is JSON or plain text
  *
  */
-void stdin_io_first_line_cb(struct ev_loop *loop, ev_io *watcher, int revents) {
+static void stdin_io_first_line_cb(struct ev_loop *loop, ev_io *watcher, int revents) {
     int rec;
     unsigned char *buffer = get_buffer(watcher, &rec);
     if (buffer == NULL)
@@ -457,7 +457,7 @@ void stdin_io_first_line_cb(struct ev_loop *loop, ev_io *watcher, int revents) {
  * anymore
  *
  */
-void child_sig_cb(struct ev_loop *loop, ev_child *watcher, int revents) {
+static void child_sig_cb(struct ev_loop *loop, ev_child *watcher, int revents) {
     int exit_status = WEXITSTATUS(watcher->rstatus);
 
     ELOG("Child (pid: %d) unexpectedly exited with status %d\n",
@@ -477,7 +477,7 @@ void child_sig_cb(struct ev_loop *loop, ev_child *watcher, int revents) {
     draw_bars(false);
 }
 
-void child_write_output(void) {
+static void child_write_output(void) {
     if (child.click_events) {
         const unsigned char *output;
         size_t size;
@@ -580,7 +580,7 @@ void start_child(char *command) {
     atexit(kill_child_at_exit);
 }
 
-void child_click_events_initialize(void) {
+static void child_click_events_initialize(void) {
     if (!child.click_events_init) {
         yajl_gen_array_open(gen);
         child_write_output();
@@ -588,7 +588,7 @@ void child_click_events_initialize(void) {
     }
 }
 
-void child_click_events_key(const char *key) {
+static void child_click_events_key(const char *key) {
     yajl_gen_string(gen, (const unsigned char *)key, strlen(key));
 }
 
diff --git a/i3bar/src/ipc.c b/i3bar/src/ipc.c
index 9a7fb21e..df5a12cf 100644
--- a/i3bar/src/ipc.c
+++ b/i3bar/src/ipc.c
@@ -34,7 +34,7 @@ typedef void (*handler_t)(char *);
  * Since i3 does not give us much feedback on commands, we do not much
  *
  */
-void got_command_reply(char *reply) {
+static void got_command_reply(char *reply) {
     /* TODO: Error handling for command replies */
 }
 
@@ -42,7 +42,7 @@ void got_command_reply(char *reply) {
  * Called, when we get a reply with workspaces data
  *
  */
-void got_workspace_reply(char *reply) {
+static void got_workspace_reply(char *reply) {
     DLOG("Got workspace data!\n");
     parse_workspaces_json(reply);
     draw_bars(false);
@@ -53,7 +53,7 @@ void got_workspace_reply(char *reply) {
  * Since i3 does not give us much feedback on commands, we do not much
  *
  */
-void got_subscribe_reply(char *reply) {
+static void got_subscribe_reply(char *reply) {
     DLOG("Got subscribe reply: %s\n", reply);
     /* TODO: Error handling for subscribe commands */
 }
@@ -62,7 +62,7 @@ void got_subscribe_reply(char *reply) {
  * Called, when we get a reply with outputs data
  *
  */
-void got_output_reply(char *reply) {
+static void got_output_reply(char *reply) {
     DLOG("Clearing old output configuration...\n");
     free_outputs();
 
@@ -87,7 +87,7 @@ void got_output_reply(char *reply) {
  * Called when we get the configuration for our bar instance
  *
  */
-void got_bar_config(char *reply) {
+static void got_bar_config(char *reply) {
     DLOG("Received bar config \"%s\"\n", reply);
     /* We initiate the main function by requesting infos about the outputs and
      * workspaces. Everything else (creating the bars, showing the right workspace-
@@ -132,7 +132,7 @@ handler_t reply_handlers[] = {
  * Called, when a workspace event arrives (i.e. the user changed the workspace)
  *
  */
-void got_workspace_event(char *event) {
+static void got_workspace_event(char *event) {
     DLOG("Got workspace event!\n");
     i3_send_msg(I3_IPC_MESSAGE_TYPE_GET_WORKSPACES, NULL);
 }
@@ -141,7 +141,7 @@ void got_workspace_event(char *event) {
  * Called, when an output event arrives (i.e. the screen configuration changed)
  *
  */
-void got_output_event(char *event) {
+static void got_output_event(char *event) {
     DLOG("Got output event!\n");
     i3_send_msg(I3_IPC_MESSAGE_TYPE_GET_OUTPUTS, NULL);
     if (!config.disable_ws) {
@@ -153,7 +153,7 @@ void got_output_event(char *event) {
  * Called, when a mode event arrives (i3 changed binding mode).
  *
  */
-void got_mode_event(char *event) {
+static void got_mode_event(char *event) {
     DLOG("Got mode event!\n");
     parse_mode_json(event);
     draw_bars(false);
@@ -163,7 +163,7 @@ void got_mode_event(char *event) {
  * Called, when a barconfig_update event arrives (i.e. i3 changed the bar hidden_state or mode)
  *
  */
-void got_bar_config_update(char *event) {
+static void got_bar_config_update(char *event) {
     /* check whether this affect this bar instance by checking the bar_id */
     char *expected_id;
     sasprintf(&expected_id, "\"id\":\"%s\"", config.bar_id);
@@ -213,7 +213,7 @@ handler_t event_handlers[] = {
  * Called, when we get a message from i3
  *
  */
-void got_data(struct ev_loop *loop, ev_io *watcher, int events) {
+static void got_data(struct ev_loop *loop, ev_io *watcher, int events) {
     DLOG("Got data!\n");
     int fd = watcher->fd;
 
diff --git a/i3bar/src/main.c b/i3bar/src/main.c
index f90bb312..a818dd97 100644
--- a/i3bar/src/main.c
+++ b/i3bar/src/main.c
@@ -44,7 +44,7 @@ void debuglog(char *fmt, ...) {
  * Glob path, i.e. expand ~
  *
  */
-char *expand_path(char *path) {
+static char *expand_path(char *path) {
     static glob_t globbuf;
     if (glob(path, GLOB_NOCHECK | GLOB_TILDE, NULL, &globbuf) < 0) {
         ELOG("glob() failed\n");
@@ -55,7 +55,7 @@ char *expand_path(char *path) {
     return result;
 }
 
-void print_usage(char *elf_name) {
+static void print_usage(char *elf_name) {
     printf("Usage: %s -b bar_id [-s sock_path] [-h] [-v]\n", elf_name);
     printf("\n");
     printf("-b, --bar_id  <bar_id>\tBar ID for which to get the configuration\n");
@@ -76,7 +76,7 @@ void print_usage(char *elf_name) {
  * in main() with that
  *
  */
-void sig_cb(struct ev_loop *loop, ev_signal *watcher, int revents) {
+static void sig_cb(struct ev_loop *loop, ev_signal *watcher, int revents) {
     switch (watcher->signum) {
         case SIGTERM:
             DLOG("Got a SIGTERM, stopping\n");
diff --git a/i3bar/src/xcb.c b/i3bar/src/xcb.c
index f4509c26..66003425 100644
--- a/i3bar/src/xcb.c
+++ b/i3bar/src/xcb.c
@@ -146,13 +146,13 @@ int _xcb_request_failed(xcb_void_cookie_t cookie, char *err_msg, int line) {
     return 0;
 }
 
-uint32_t get_sep_offset(struct status_block *block) {
+static uint32_t get_sep_offset(struct status_block *block) {
     if (!block->no_separator && block->sep_block_width > 0)
         return block->sep_block_width / 2 + block->sep_block_width % 2;
     return 0;
 }
 
-int get_tray_width(struct tc_head *trayclients) {
+static int get_tray_width(struct tc_head *trayclients) {
     trayclient *trayclient;
     int tray_width = 0;
     TAILQ_FOREACH_REVERSE(trayclient, trayclients, tc_head, tailq) {
@@ -193,7 +193,7 @@ static void draw_separator(i3_output *output, uint32_t x, struct status_block *b
     }
 }
 
-uint32_t predict_statusline_length(bool use_short_text) {
+static uint32_t predict_statusline_length(bool use_short_text) {
     uint32_t width = 0;
     struct status_block *block;
 
@@ -245,7 +245,7 @@ uint32_t predict_statusline_length(bool use_short_text) {
 /*
  * Redraws the statusline to the output's statusline_buffer
  */
-void draw_statusline(i3_output *output, uint32_t clip_left, bool use_focus_colors, bool use_short_text) {
+static void draw_statusline(i3_output *output, uint32_t clip_left, bool use_focus_colors, bool use_short_text) {
     struct status_block *block;
 
     color_t bar_color = (use_focus_colors ? colors.focus_bar_bg : colors.bar_bg);
@@ -330,7 +330,7 @@ void draw_statusline(i3_output *output, uint32_t clip_left, bool use_focus_color
  * Hides all bars (unmaps them)
  *
  */
-void hide_bars(void) {
+static void hide_bars(void) {
     if ((config.hide_on_modifier == M_DOCK) || (config.hidden_state == S_SHOW && config.hide_on_modifier == M_HIDE)) {
         return;
     }
@@ -349,7 +349,7 @@ void hide_bars(void) {
  * Unhides all bars (maps them)
  *
  */
-void unhide_bars(void) {
+static void unhide_bars(void) {
     if (config.hide_on_modifier != M_HIDE) {
         return;
     }
@@ -457,7 +457,7 @@ static bool execute_custom_command(xcb_keycode_t input_code, bool event_is_relea
  * wheel was used and change the workspace appropriately
  *
  */
-void handle_button(xcb_button_press_event_t *event) {
+static void handle_button(xcb_button_press_event_t *event) {
     /* Determine, which bar was clicked */
     i3_output *walk;
     xcb_window_t bar = event->event;
@@ -1080,7 +1080,7 @@ static void handle_resize_request(xcb_resize_request_event_t *event) {
  * events from X11, handle them, then flush our outgoing queue.
  *
  */
-void xcb_prep_cb(struct ev_loop *loop, ev_prepare *watcher, int revents) {
+static void xcb_prep_cb(struct ev_loop *loop, ev_prepare *watcher, int revents) {
     xcb_generic_event_t *event;
 
     if (xcb_connection_has_error(xcb_connection)) {
@@ -1177,7 +1177,7 @@ void xcb_prep_cb(struct ev_loop *loop, ev_prepare *watcher, int revents) {
  * are triggered
  *
  */
-void xcb_io_cb(struct ev_loop *loop, ev_io *watcher, int revents) {
+static void xcb_io_cb(struct ev_loop *loop, ev_io *watcher, int revents) {
 }
 
 /*
@@ -1185,7 +1185,7 @@ void xcb_io_cb(struct ev_loop *loop, ev_io *watcher, int revents) {
  * depend on 'config'.
  *
  */
-char *init_xcb_early() {
+char *init_xcb_early(void) {
     /* FIXME: xcb_connect leaks memory */
     xcb_connection = xcb_connect(NULL, &screen);
     if (xcb_connection_has_error(xcb_connection)) {
@@ -1248,7 +1248,7 @@ char *init_xcb_early() {
  * in xcb.
  *
  */
-void register_xkb_keyevents() {
+static void register_xkb_keyevents(void) {
     const xcb_query_extension_reply_t *extreply;
     extreply = xcb_get_extension_data(conn, &xcb_xkb_id);
     if (!extreply->present) {
@@ -1272,7 +1272,7 @@ void register_xkb_keyevents() {
  * Deregister from xkb keyevents.
  *
  */
-void deregister_xkb_keyevents() {
+static void deregister_xkb_keyevents(void) {
     xcb_xkb_select_events(conn,
                           XCB_XKB_ID_USE_CORE_KBD,
                           0,
@@ -1338,7 +1338,7 @@ static void send_tray_clientmessage(void) {
  * atom. Afterwards, tray clients will send ClientMessages to our window.
  *
  */
-void init_tray(void) {
+static void init_tray(void) {
     DLOG("Initializing system tray functionality\n");
     /* request the tray manager atom for the X11 display we are running on */
     char atomname[strlen("_NET_SYSTEM_TRAY_S") + 11];
@@ -1567,7 +1567,7 @@ void destroy_window(i3_output *output) {
 
 /* Strut partial tells i3 where to reserve space for i3bar. This is determined
  * by the `position` bar config directive. */
-xcb_void_cookie_t config_strut_partial(i3_output *output) {
+static xcb_void_cookie_t config_strut_partial(i3_output *output) {
     /* A local struct to save the strut_partial property */
     struct {
         uint32_t left;
diff --git a/include/commands.h b/include/commands.h
index b4b3da38..0137460f 100644
--- a/include/commands.h
+++ b/include/commands.h
@@ -314,13 +314,13 @@ void cmd_rename_workspace(I3_CMD, const char *old_name, const char *new_name);
  */
 void cmd_bar(I3_CMD, const char *bar_type, const char *bar_value, const char *bar_id);
 
-/*
+/**
  * Implementation of 'shmlog <size>|toggle|on|off'
  *
  */
 void cmd_shmlog(I3_CMD, const char *argument);
 
-/*
+/**
  * Implementation of 'debuglog toggle|on|off'
  *
  */
diff --git a/include/commands_parser.h b/include/commands_parser.h
index 88b3f6d0..b65ae93f 100644
--- a/include/commands_parser.h
+++ b/include/commands_parser.h
@@ -13,7 +13,7 @@
 
 #include <yajl/yajl_gen.h>
 
-/*
+/**
  * Holds an intermediate represenation of the result of a call to any command.
  * When calling parse_command("floating enable, border none"), the parser will
  * internally use this struct when calling cmd_floating and cmd_border.
diff --git a/include/con.h b/include/con.h
index 672d80ac..2c991b0c 100644
--- a/include/con.h
+++ b/include/con.h
@@ -20,7 +20,8 @@
  */
 Con *con_new_skeleton(Con *parent, i3Window *window);
 
-/* A wrapper for con_new_skeleton, to retain the old con_new behaviour
+/**
+ * A wrapper for con_new_skeleton, to retain the old con_new behaviour
  *
  */
 Con *con_new(Con *parent, i3Window *window);
@@ -220,7 +221,7 @@ void con_mark_toggle(Con *con, const char *mark, mark_mode_t mode);
  */
 void con_mark(Con *con, const char *mark, mark_mode_t mode);
 
-/*
+/**
  * Removes marks from containers.
  * If con is NULL, all containers are considered.
  * If name is NULL, this removes all existing marks.
@@ -402,7 +403,7 @@ Con *con_descend_focused(Con *con);
  */
 Con *con_descend_tiling_focused(Con *con);
 
-/*
+/**
  * Returns the leftmost, rightmost, etc. container in sub-tree. For example, if
  * direction is D_LEFT, then we return the rightmost container and if direction
  * is D_RIGHT, we return the leftmost container.  This is because if we are
diff --git a/include/config_parser.h b/include/config_parser.h
index ace4041d..009538f2 100644
--- a/include/config_parser.h
+++ b/include/config_parser.h
@@ -16,7 +16,7 @@
 SLIST_HEAD(variables_head, Variable);
 extern pid_t config_error_nagbar_pid;
 
-/*
+/**
  * An intermediate reprsentation of the result of a parse_config call.
  * Currently unused, but the JSON output will be useful in the future when we
  * implement a config parsing IPC command.
diff --git a/include/configuration.h b/include/configuration.h
index 3eccca4c..d99d9fff 100644
--- a/include/configuration.h
+++ b/include/configuration.h
@@ -427,7 +427,7 @@ void ungrab_all_keys(xcb_connection_t *conn);
  * Sends the current bar configuration as an event to all barconfig_update listeners.
  *
  */
-void update_barconfig();
+void update_barconfig(void);
 
 /**
  * Kills the configerror i3-nagbar process, if any.
diff --git a/include/libi3.h b/include/libi3.h
index d27437ba..790baba9 100644
--- a/include/libi3.h
+++ b/include/libi3.h
@@ -343,7 +343,7 @@ uint32_t get_colorpixel(const char *hex) __attribute__((const));
 
 #if defined(__APPLE__)
 
-/*
+/**
  * Taken from FreeBSD
  * Returns a pointer to a new string which is a duplicate of the
  * string, but only copies at most n characters.
@@ -472,7 +472,7 @@ xcb_visualtype_t *get_visualtype(xcb_screen_t *screen);
  * release version), based on the git version number.
  *
  */
-bool is_debug_build() __attribute__((const));
+bool is_debug_build(void) __attribute__((const));
 
 /**
  * Returns the name of a temporary file with the specified prefix.
diff --git a/include/match.h b/include/match.h
index 4ff8c485..043c3a8f 100644
--- a/include/match.h
+++ b/include/match.h
@@ -15,7 +15,7 @@
 
 #include <config.h>
 
-/*
+/**
  * Initializes the Match data structure. This function is necessary because the
  * members representing boolean values (like dock) need to be initialized with
  * -1 instead of 0.
diff --git a/include/randr.h b/include/randr.h
index 39182c54..ec533a28 100644
--- a/include/randr.h
+++ b/include/randr.h
@@ -137,7 +137,7 @@ Output *get_output_next(direction_t direction, Output *current, output_close_far
  */
 Output *get_output_next_wrap(direction_t direction, Output *current);
 
-/*
+/**
  * Creates an output covering the root window.
  *
  */
diff --git a/include/render.h b/include/render.h
index 750b7d31..2b2c8dad 100644
--- a/include/render.h
+++ b/include/render.h
@@ -12,7 +12,10 @@
 
 #include <config.h>
 
-/* This is used to keep a state to pass around when rendering a con in render_con(). */
+/**
+ * This is used to keep a state to pass around when rendering a con in render_con().
+ *
+ */
 typedef struct render_params {
     /* A copy of the coordinates of the container which is being rendered. */
     int x;
@@ -39,7 +42,8 @@ typedef struct render_params {
  */
 void render_con(Con *con, bool render_fullscreen);
 
-/*
+/**
  * Returns the height for the decorations
+ *
  */
 int render_deco_height(void);
diff --git a/include/shmlog.h b/include/shmlog.h
index b90211ef..dc8081f1 100644
--- a/include/shmlog.h
+++ b/include/shmlog.h
@@ -20,7 +20,7 @@
 /* Default shmlog size if not set by user. */
 extern const int default_shmlog_size;
 
-/*
+/**
  * Header of the shmlog file. Used by i3/src/log.c and i3/i3-dump-log/main.c.
  *
  */
diff --git a/include/startup.h b/include/startup.h
index 5da221e1..feece575 100644
--- a/include/startup.h
+++ b/include/startup.h
@@ -21,7 +21,7 @@
  * Starts the given application by passing it through a shell. We use double
  * fork to avoid zombie processes. As the started application’s parent exits
  * (immediately), the application is reparented to init (process-id 1), which
- * correctly handles childs, so we don’t have to do it :-).
+ * correctly handles children, so we don’t have to do it :-).
  *
  * The shell used to start applications is the system's bourne shell (i.e.,
  * /bin/sh).
diff --git a/include/util.h b/include/util.h
index 90ddc4a4..d08ac69d 100644
--- a/include/util.h
+++ b/include/util.h
@@ -125,7 +125,7 @@ void i3_restart(bool forget_layout);
 
 #if defined(__OpenBSD__) || defined(__APPLE__)
 
-/*
+/**
  * Taken from FreeBSD
  * Find the first occurrence of the byte string s in byte string l.
  *
diff --git a/libi3/dpi.c b/libi3/dpi.c
index a2c40319..d15e35be 100644
--- a/libi3/dpi.c
+++ b/libi3/dpi.c
@@ -49,14 +49,12 @@ void init_dpi(void) {
         dpi = 0;
         goto init_dpi_end;
     }
-    dpi = (long)round(in_dpi);
+    dpi = lround(in_dpi);
 
     DLOG("Found Xft.dpi = %ld.\n", dpi);
 
 init_dpi_end:
-    if (resource != NULL) {
-        free(resource);
-    }
+    free(resource);
 
     if (database != NULL) {
         xcb_xrm_database_free(database);
diff --git a/libi3/draw_util.c b/libi3/draw_util.c
index 6a2e93dc..f88360dc 100644
--- a/libi3/draw_util.c
+++ b/libi3/draw_util.c
@@ -121,7 +121,7 @@ static void draw_util_set_source_color(surface_t *surface, color_t color) {
     cairo_set_source_rgba(surface->cr, color.red, color.green, color.blue, color.alpha);
 }
 
-/**
+/*
  * Draw the given text using libi3.
  * This function also marks the surface dirty which is needed if other means of
  * drawing are used. This will be the case when using XCB to draw text.
@@ -140,7 +140,7 @@ void draw_util_text(i3String *text, surface_t *surface, color_t fg_color, color_
     cairo_surface_mark_dirty(surface->surface);
 }
 
-/**
+/*
  * Draws a filled rectangle.
  * This function is a convenience wrapper and takes care of flushing the
  * surface as well as restoring the cairo state.
@@ -167,7 +167,7 @@ void draw_util_rectangle(surface_t *surface, color_t color, double x, double y,
     cairo_restore(surface->cr);
 }
 
-/**
+/*
  * Clears a surface with the given color.
  *
  */
@@ -191,7 +191,7 @@ void draw_util_clear_surface(surface_t *surface, color_t color) {
     cairo_restore(surface->cr);
 }
 
-/**
+/*
  * Copies a surface onto another surface.
  *
  */
diff --git a/libi3/font.c b/libi3/font.c
index 3dca8124..7be84ee0 100644
--- a/libi3/font.c
+++ b/libi3/font.c
@@ -224,9 +224,7 @@ i3Font load_font(const char *pattern, const bool fallback) {
                      error->error_code);
         }
     }
-    if (error != NULL) {
-        free(error);
-    }
+    free(error);
 
     font.pattern = sstrdup(pattern);
     LOG("Using X font %s\n", pattern);
@@ -275,8 +273,7 @@ void free_font(void) {
         case FONT_TYPE_XCB: {
             /* Close the font and free the info */
             xcb_close_font(conn, savedFont->specific.xcb.id);
-            if (savedFont->specific.xcb.info)
-                free(savedFont->specific.xcb.info);
+            free(savedFont->specific.xcb.info);
             break;
         }
         case FONT_TYPE_PANGO:
diff --git a/libi3/is_debug_build.c b/libi3/is_debug_build.c
index 4e583622..52187bda 100644
--- a/libi3/is_debug_build.c
+++ b/libi3/is_debug_build.c
@@ -15,7 +15,7 @@
  * release version), based on the git version number.
  *
  */
-bool is_debug_build() {
+bool is_debug_build(void) {
     /* i3_version contains either something like this:
      *     "4.0.2 (2011-11-11, branch "release")".
      * or: "4.0.2-123-gCOFFEEBABE (2011-11-11, branch "next")".
diff --git a/libi3/string.c b/libi3/string.c
index a078b33e..9efa3690 100644
--- a/libi3/string.c
+++ b/libi3/string.c
@@ -99,7 +99,7 @@ i3String *i3string_from_ucs2(const xcb_char2b_t *from_ucs2, size_t num_glyphs) {
     return str;
 }
 
-/**
+/*
  * Copies the given i3string.
  * Note that this will not free the source string.
  */
diff --git a/src/bindings.c b/src/bindings.c
index ad5fe4f3..6704c816 100644
--- a/src/bindings.c
+++ b/src/bindings.c
@@ -859,8 +859,6 @@ static int fill_rmlvo_from_root(struct xkb_rule_names *xkb_names) {
     xcb_intern_atom_reply_t *atom_reply;
     size_t content_max_words = 256;
 
-    xcb_window_t root = root_screen->root;
-
     atom_reply = xcb_intern_atom_reply(
         conn, xcb_intern_atom(conn, 0, strlen("_XKB_RULES_NAMES"), "_XKB_RULES_NAMES"), NULL);
     if (atom_reply == NULL)
diff --git a/src/commands.c b/src/commands.c
index 70f3bf18..eecd59fc 100644
--- a/src/commands.c
+++ b/src/commands.c
@@ -330,7 +330,7 @@ void cmd_move_con_to_workspace(I3_CMD, const char *which) {
     ysuccess(true);
 }
 
-/**
+/*
  * Implementation of 'move [window|container] [to] workspace back_and_forth'.
  *
  */
@@ -2034,7 +2034,7 @@ void cmd_rename_workspace(I3_CMD, const char *old_name, const char *new_name) {
  * Implementation of 'bar mode dock|hide|invisible|toggle [<bar_id>]'
  *
  */
-bool cmd_bar_mode(const char *bar_mode, const char *bar_id) {
+static bool cmd_bar_mode(const char *bar_mode, const char *bar_id) {
     int mode = M_DOCK;
     bool toggle = false;
     if (strcmp(bar_mode, "dock") == 0)
@@ -2079,7 +2079,7 @@ bool cmd_bar_mode(const char *bar_mode, const char *bar_id) {
  * Implementation of 'bar hidden_state hide|show|toggle [<bar_id>]'
  *
  */
-bool cmd_bar_hidden_state(const char *bar_hidden_state, const char *bar_id) {
+static bool cmd_bar_hidden_state(const char *bar_hidden_state, const char *bar_id) {
     int hidden_state = S_SHOW;
     bool toggle = false;
     if (strcmp(bar_hidden_state, "hide") == 0)
diff --git a/src/commands_parser.c b/src/commands_parser.c
index 98f06659..4299c008 100644
--- a/src/commands_parser.c
+++ b/src/commands_parser.c
@@ -157,7 +157,7 @@ static long get_long(const char *identifier) {
 // TODO move to a common util
 static void clear_stack(void) {
     for (int c = 0; c < 10; c++) {
-        if (stack[c].type == STACK_STR && stack[c].val.str != NULL)
+        if (stack[c].type == STACK_STR)
             free(stack[c].val.str);
         stack[c].identifier = NULL;
         stack[c].val.str = NULL;
diff --git a/src/con.c b/src/con.c
index d50c29be..c9ff44a2 100644
--- a/src/con.c
+++ b/src/con.c
@@ -312,7 +312,7 @@ bool con_has_managed_window(Con *con) {
     return (con != NULL && con->window != NULL && con->window->id != XCB_WINDOW_NONE && con_get_workspace(con) != NULL);
 }
 
-/**
+/*
  * Returns true if this node has regular or floating children.
  *
  */
@@ -526,7 +526,7 @@ Con *con_get_fullscreen_covering_ws(Con *ws) {
     return fs;
 }
 
-/**
+/*
  * Returns true if the container is internal, such as __i3_scratch
  *
  */
@@ -896,7 +896,7 @@ int con_num_children(Con *con) {
     return children;
 }
 
-/**
+/*
  * Returns the number of visible non-floating children of this container.
  * For example, if the container contains a hsplit which has two children,
  * this will return 2 instead of 1.
diff --git a/src/config.c b/src/config.c
index 5be1fd52..9631b216 100644
--- a/src/config.c
+++ b/src/config.c
@@ -18,7 +18,7 @@ Config config;
 struct modes_head modes;
 struct barconfig_head barconfigs = TAILQ_HEAD_INITIALIZER(barconfigs);
 
-/**
+/*
  * Ungrabs all keys, to be called before re-grabbing the keys because of a
  * mapping_notify event or a configuration file reload
  *
@@ -32,7 +32,7 @@ void ungrab_all_keys(xcb_connection_t *conn) {
  * Sends the current bar configuration as an event to all barconfig_update listeners.
  *
  */
-void update_barconfig() {
+void update_barconfig(void) {
     Barconfig *current;
     TAILQ_FOREACH(current, &barconfigs, configs) {
         ipc_send_barconfig_update_event(current);
diff --git a/src/config_parser.c b/src/config_parser.c
index 2d3f3bb9..9f972fed 100644
--- a/src/config_parser.c
+++ b/src/config_parser.c
@@ -171,7 +171,7 @@ static long get_long(const char *identifier) {
 
 static void clear_stack(void) {
     for (int c = 0; c < 10; c++) {
-        if (stack[c].type == STACK_STR && stack[c].val.str != NULL)
+        if (stack[c].type == STACK_STR)
             free(stack[c].val.str);
         stack[c].identifier = NULL;
         stack[c].val.str = NULL;
diff --git a/src/floating.c b/src/floating.c
index be514ce2..a99d0970 100644
--- a/src/floating.c
+++ b/src/floating.c
@@ -59,7 +59,7 @@ static void floating_set_hint_atom(Con *con, bool floating) {
     xcb_flush(conn);
 }
 
-/**
+/*
  * Called when a floating window is created or resized.
  * This function resizes the window if its size is higher or lower than the
  * configured maximum/minimum size, respectively.
@@ -899,13 +899,17 @@ bool floating_reposition(Con *con, Rect newrect) {
 
     con->rect = newrect;
 
-    floating_maybe_reassign_ws(con);
+    bool reassigned = floating_maybe_reassign_ws(con);
 
     /* If this is a scratchpad window, don't auto center it from now on. */
     if (con->scratchpad_state == SCRATCHPAD_FRESH)
         con->scratchpad_state = SCRATCHPAD_CHANGED;
 
-    tree_render();
+    /* Workspace change will already result in a tree_render. */
+    if (!reassigned) {
+        render_con(con, false);
+        x_push_node(con);
+    }
     return true;
 }
 
diff --git a/src/handlers.c b/src/handlers.c
index c76f1935..238cf26f 100644
--- a/src/handlers.c
+++ b/src/handlers.c
@@ -949,8 +949,8 @@ static void handle_client_message(xcb_client_message_event_t *event) {
     }
 }
 
-bool handle_window_type(void *data, xcb_connection_t *conn, uint8_t state, xcb_window_t window,
-                        xcb_atom_t atom, xcb_get_property_reply_t *reply) {
+static bool handle_window_type(void *data, xcb_connection_t *conn, uint8_t state, xcb_window_t window,
+                               xcb_atom_t atom, xcb_get_property_reply_t *reply) {
     Con *con;
     if ((con = con_by_window_id(window)) == NULL || con->window == NULL)
         return false;
diff --git a/src/ipc.c b/src/ipc.c
index 3022d5b3..d0fb965c 100644
--- a/src/ipc.c
+++ b/src/ipc.c
@@ -1580,7 +1580,7 @@ void ipc_send_workspace_event(const char *change, Con *current, Con *old) {
     y(free);
 }
 
-/**
+/*
  * For the window events we send, along the usual "change" field,
  * also the window container, in "container".
  */
@@ -1610,7 +1610,7 @@ void ipc_send_window_event(const char *property, Con *con) {
     setlocale(LC_NUMERIC, "");
 }
 
-/**
+/*
  * For the barconfig update events, we send the serialized barconfig.
  */
 void ipc_send_barconfig_update_event(Barconfig *barconfig) {
diff --git a/src/load_layout.c b/src/load_layout.c
index 32da9c47..5a340d2c 100644
--- a/src/load_layout.c
+++ b/src/load_layout.c
@@ -153,8 +153,7 @@ static int json_end_map(void *ctx) {
                 free(marks[i]);
             }
 
-            free(marks);
-            marks = NULL;
+            FREE(marks);
             num_marks = 0;
         }
 
diff --git a/src/main.c b/src/main.c
index eeeb3419..7eb47c82 100644
--- a/src/main.c
+++ b/src/main.c
@@ -32,7 +32,7 @@
  * RLIM_INFINITY for i3 debugging versions. */
 struct rlimit original_rlimit_core;
 
-/** The number of file descriptors passed via socket activation. */
+/* The number of file descriptors passed via socket activation. */
 int listen_fds;
 
 /* We keep the xcb_prepare watcher around to be able to enable and disable it
diff --git a/src/manage.c b/src/manage.c
index 4031ade6..c4706b0d 100644
--- a/src/manage.c
+++ b/src/manage.c
@@ -246,17 +246,13 @@ void manage_window(xcb_window_t window, xcb_get_window_attributes_cookie_t cooki
 
     DLOG("Initial geometry: (%d, %d, %d, %d)\n", geom->x, geom->y, geom->width, geom->height);
 
-    Con *nc = NULL;
-    Match *match = NULL;
-    Assignment *assignment;
-
-    /* TODO: two matches for one container */
-
     /* See if any container swallows this new window */
-    nc = con_for_window(search_at, cwindow, &match);
+    Match *match = NULL;
+    Con *nc = con_for_window(search_at, cwindow, &match);
     const bool match_from_restart_mode = (match && match->restart_mode);
     if (nc == NULL) {
         Con *wm_desktop_ws = NULL;
+        Assignment *assignment;
 
         /* If not, check if it is assigned to a specific workspace */
         if ((assignment = assignment_for(cwindow, A_TO_WORKSPACE)) ||
diff --git a/src/randr.c b/src/randr.c
index 54d61ddd..6bb8d9e6 100644
--- a/src/randr.c
+++ b/src/randr.c
@@ -550,7 +550,7 @@ static void output_change_mode(xcb_connection_t *conn, Output *output) {
     }
 
     /* If default_orientation is NO_ORIENTATION, we change the orientation of
-     * the workspaces and their childs depending on output resolution. This is
+     * the workspaces and their children depending on output resolution. This is
      * only done for workspaces with maximum one child. */
     if (config.default_orientation == NO_ORIENTATION) {
         TAILQ_FOREACH(workspace, &(content->nodes_head), nodes) {
diff --git a/src/sighandler.c b/src/sighandler.c
index 12ed0ef9..e49c30ba 100644
--- a/src/sighandler.c
+++ b/src/sighandler.c
@@ -62,14 +62,13 @@ static int sighandler_backtrace(void) {
 
     char *filename = NULL;
     int suffix = 0;
-    struct stat bt;
     /* Find a unique filename for the backtrace (since the PID of i3 stays the
      * same), so that we don’t overwrite earlier backtraces. */
     do {
         FREE(filename);
         sasprintf(&filename, "%s/i3-backtrace.%d.%d.txt", tmpdir, pid_parent, suffix);
         suffix++;
-    } while (stat(filename, &bt) == 0);
+    } while (path_exists(filename));
 
     pid_t pid_gdb = fork();
     if (pid_gdb < 0) {
@@ -130,7 +129,7 @@ static int sighandler_backtrace(void) {
     if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
         DLOG("GDB did not run properly\n");
         return -1;
-    } else if (stat(filename, &bt) == -1) {
+    } else if (!path_exists(filename)) {
         DLOG("GDB executed successfully, but no backtrace was generated\n");
         return -1;
     }
@@ -300,7 +299,7 @@ static void sighandler_handle_key_press(xcb_key_press_event_t *event) {
     }
 }
 
-void handle_signal(int sig, siginfo_t *info, void *data) {
+static void handle_signal(int sig, siginfo_t *info, void *data) {
     DLOG("i3 crashed. SIG: %d\n", sig);
 
     struct sigaction action;
diff --git a/src/startup.c b/src/startup.c
index b1a2f602..6302d811 100644
--- a/src/startup.c
+++ b/src/startup.c
@@ -95,7 +95,7 @@ static int _prune_startup_sequences(void) {
     return active_sequences;
 }
 
-/**
+/*
  * Deletes a startup sequence, ignoring whether its timeout has elapsed.
  * Useful when e.g. a window is moved between workspaces and its children
  * shouldn't spawn on the original workspace.
@@ -118,10 +118,10 @@ void startup_sequence_delete(struct Startup_Sequence *sequence) {
 }
 
 /*
- * Starts the given application by passing it through a shell. We use double fork
- * to avoid zombie processes. As the started application’s parent exits (immediately),
- * the application is reparented to init (process-id 1), which correctly handles
- * childs, so we don’t have to do it :-).
+ * Starts the given application by passing it through a shell. We use double
+ * fork to avoid zombie processes. As the started application’s parent exits
+ * (immediately), the application is reparented to init (process-id 1), which
+ * correctly handles children, so we don’t have to do it :-).
  *
  * The shell used to start applications is the system's bourne shell (i.e.,
  * /bin/sh).
@@ -257,7 +257,7 @@ void startup_monitor_event(SnMonitorEvent *event, void *userdata) {
     }
 }
 
-/**
+/*
  * Renames workspaces that are mentioned in the startup sequences.
  *
  */
@@ -273,7 +273,7 @@ void startup_sequence_rename_workspace(const char *old_name, const char *new_nam
     }
 }
 
-/**
+/*
  * Gets the stored startup sequence for the _NET_STARTUP_ID of a given window.
  *
  */
diff --git a/src/util.c b/src/util.c
index a59283a8..85f359c0 100644
--- a/src/util.c
+++ b/src/util.c
@@ -217,7 +217,7 @@ static char **add_argument(char **original, char *opt_char, char *opt_arg, char
 #define y(x, ...) yajl_gen_##x(gen, ##__VA_ARGS__)
 #define ystr(str) yajl_gen_string(gen, (unsigned char *)str, strlen(str))
 
-char *store_restart_layout(void) {
+static char *store_restart_layout(void) {
     setlocale(LC_NUMERIC, "C");
     yajl_gen gen = yajl_gen_alloc(NULL);
 
@@ -501,8 +501,7 @@ ssize_t slurp(const char *path, char **buf) {
     fclose(f);
     if ((ssize_t)n != stbuf.st_size) {
         ELOG("File \"%s\" could not be read entirely: got %zd, want %" PRIi64 "\n", path, n, (int64_t)stbuf.st_size);
-        free(*buf);
-        *buf = NULL;
+        FREE(*buf);
         return -1;
     }
     return (ssize_t)n;
diff --git a/src/workspace.c b/src/workspace.c
index 5f5c8d4f..882dac54 100644
--- a/src/workspace.c
+++ b/src/workspace.c
@@ -308,7 +308,7 @@ bool workspace_is_visible(Con *ws) {
  * XXX: we need to clean up all this recursive walking code.
  *
  */
-Con *_get_sticky(Con *con, const char *sticky_group, Con *exclude) {
+static Con *_get_sticky(Con *con, const char *sticky_group, Con *exclude) {
     Con *current;
 
     TAILQ_FOREACH(current, &(con->nodes_head), nodes) {
@@ -914,7 +914,7 @@ Con *workspace_attach_to(Con *ws) {
     return new;
 }
 
-/**
+/*
  * Creates a new container and re-parents all of children from the given
  * workspace into it.
  *
@@ -949,7 +949,7 @@ Con *workspace_encapsulate(Con *ws) {
     return new;
 }
 
-/**
+/*
  * Move the given workspace to the specified output.
  * This returns true if and only if moving the workspace was successful.
  */
diff --git a/src/x.c b/src/x.c
index 1f54db83..6a0170a5 100644
--- a/src/x.c
+++ b/src/x.c
@@ -42,7 +42,7 @@ typedef struct con_state {
     bool child_mapped;
     bool is_hidden;
 
-    /** The con for which this state is. */
+    /* The con for which this state is. */
     Con *con;
 
     /* For reparenting, we have a flag (need_reparent) and the X ID of the old
@@ -504,14 +504,12 @@ void x_draw_decoration(Con *con) {
     /* 3: draw a rectangle in border color around the client */
     if (p->border_style != BS_NONE && p->con_is_leaf) {
         /* We might hide some borders adjacent to the screen-edge */
-        adjacent_t borders_to_hide = ADJ_NONE;
-        borders_to_hide = con_adjacent_borders(con) & config.hide_edge_borders;
-
+        adjacent_t borders_to_hide = con_adjacent_borders(con) & config.hide_edge_borders;
         Rect br = con_border_style_rect(con);
 
         /* These rectangles represent the border around the child window
          * (left, bottom and right part). We don’t just fill the whole
-         * rectangle because some childs are not freely resizable and we want
+         * rectangle because some children are not freely resizable and we want
          * their background color to "shine through". */
         if (!(borders_to_hide & ADJ_LEFT_SCREEN_EDGE)) {
             draw_util_rectangle(&(con->frame_buffer), p->color->child_border, 0, 0, br.x, r->height);
@@ -1254,7 +1252,7 @@ void x_set_name(Con *con, const char *name) {
  * Set up the I3_SHMLOG_PATH atom.
  *
  */
-void update_shmlog_atom() {
+void update_shmlog_atom(void) {
     if (*shmlogname == '\0') {
         xcb_delete_property(conn, root, A_I3_SHMLOG_PATH);
     } else {
diff --git a/testcases/inject_randr1.5.c b/testcases/inject_randr1.5.c
index 5506d67e..520b0213 100644
--- a/testcases/inject_randr1.5.c
+++ b/testcases/inject_randr1.5.c
@@ -34,7 +34,7 @@ static void read_server_x11_packet_cb(EV_P_ ev_io *w, int revents);
 
 static char *sun_path = NULL;
 
-void cleanup_socket(void) {
+static void cleanup_socket(void) {
     if (sun_path != NULL) {
         unlink(sun_path);
         free(sun_path);
diff --git a/testcases/t/293-focus-follows-mouse.t b/testcases/t/293-focus-follows-mouse.t
index 0cd6e5c3..55958c3e 100644
--- a/testcases/t/293-focus-follows-mouse.t
+++ b/testcases/t/293-focus-follows-mouse.t
@@ -67,11 +67,8 @@ my $tmp = fresh_workspace;
 my ($first_floating, $second_floating);
 
 synced_warp_pointer(0, 0);
-$first_floating = open_floating_window;
-$first_floating->rect(X11::XCB::Rect->new(x => 1, y => 1, width => 100, height => 100));
-$second_floating = open_floating_window;
-$second_floating->rect(X11::XCB::Rect->new(x => 50, y => 50, width => 100, height => 100));
-sync_with_i3;
+$first_floating = open_floating_window(rect => [ 1, 1, 100, 100 ]);
+$second_floating = open_floating_window(rect => [ 50, 50, 100, 100 ]);
 $first = open_window;
 
 is($x->input_focus, $first->id, 'first (tiling) window focused');