diff --git a/Makefile b/Makefile
index 4e323b3..3278586 100644
--- a/Makefile
+++ b/Makefile
@@ -35,7 +35,7 @@ prepare:
 	@cp $(BUILD_DIR)/compile_commands.json $(MAKEFILE_DIR)
 
 build: prepare
-	${RM} -f $(TARGET)
+	${RM} $(TARGET)
 	@cmake --build $(BUILD_DIR)
 	@cp $(BUILD_DIR)/$(TARGET_NAME) $(TARGET)
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 5eeb580..46b129f 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -2,6 +2,7 @@ cmake_minimum_required(VERSION 3.24)
 
 set(APP_NAME "zdwm")
 set(SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}")
+set(BUILD_DIR "${CMAKE_CURRENT_BINARY_DIR}")
 
 add_compile_definitions(LOG_FILE="$ENV{HOME}/zdwm-log.txt")
 
@@ -18,7 +19,49 @@ project(${APP_NAME}
     LANGUAGES C
 )
 
-add_executable(${APP_NAME} main.c)
+add_executable(${APP_NAME} main.c utils.c buffer.c backtrace.c)
 
 # use C23
 set_property(TARGET ${APP_NAME} PROPERTY C_STANDARD 23)
+
+find_package(PkgConfig REQUIRED)
+
+pkg_check_modules(deps REQUIRED
+    glib-2.0
+)
+
+target_include_directories(${APP_NAME} SYSTEM
+    PRIVATE ${deps_INCLUDE_DIRS}
+)
+target_include_directories(${APP_NAME}
+    PRIVATE ${SOURCE_DIR}
+    PRIVATE ${BUILD_DIR}
+)
+
+target_link_libraries(${APP_NAME}
+    PRIVATE ${deps_LIBRARIES}
+)
+
+
+## 配置项
+# Check for backtrace_symbols()
+include(CheckSymbolExists)
+check_symbol_exists(backtrace_symbols execinfo.h HAS_EXECINFO)
+if(NOT HAS_EXECINFO)
+    find_library(LIB_EXECINFO execinfo)
+    if(LIB_EXECINFO)
+        set(HAS_EXECINFO TRUE)
+        target_link_libraries(${APP_NAME} ${LIB_EXECINFO})
+    endif()
+endif()
+if(HAS_EXECINFO)
+    message(STATUS "checking for execinfo -- found")
+else()
+    message(STATUS "checking for execinfo -- not found")
+endif()
+
+configure_file("${SOURCE_DIR}/config.h.in"
+    "${BUILD_DIR}/config.h"
+    ESCAPE_QUOTES
+    @ONLY
+)
diff --git a/src/backtrace.c b/src/backtrace.c
new file mode 100644
index 0000000..26ca326
--- /dev/null
+++ b/src/backtrace.c
@@ -0,0 +1,38 @@
+#include "backtrace.h"
+
+#include "buffer.h"
+#include "config.h"
+
+#ifdef HAS_EXECINFO
+#include <execinfo.h>
+#endif
+
+#define MAX_STACK_SIZE 32
+
+
+/**
+ * Get a backtrace.
+ * @param buffer The buffer to fill with backtrace.
+ */
+void backtrace_get(buffer_t *buffer) {
+  buffer_init(buffer);
+
+#ifdef HAS_EXECINFO
+  void *stack[MAX_STACK_SIZE];
+  char **bt;
+  int stack_size;
+
+  stack_size = backtrace(stack, countof(stack));
+  bt = backtrace_symbols(stack, stack_size);
+
+  if (bt) {
+    for (int i = 0; i < stack_size; i++) {
+      if (i > 0) buffer_addsl(buffer, "\n");
+      buffer_adds(buffer, bt[i]);
+    }
+    p_delete(&bt);
+  } else
+#endif
+
+    buffer_addsl(buffer, "Cannot get backtrace symbols.");
+}
diff --git a/src/backtrace.h b/src/backtrace.h
new file mode 100644
index 0000000..0b5947b
--- /dev/null
+++ b/src/backtrace.h
@@ -0,0 +1,5 @@
+#pragma once
+
+#include "buffer.h"
+
+void backtrace_get(buffer_t *buffer);
diff --git a/src/buffer.c b/src/buffer.c
new file mode 100644
index 0000000..a0be1ce
--- /dev/null
+++ b/src/buffer.c
@@ -0,0 +1,37 @@
+#include "buffer.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+
+#include "utils.h"
+
+char buffer_slop[1];
+
+void buffer_ensure(buffer_t *buf, int newlen) {
+  if (newlen < 0) exit(EX_SOFTWARE);
+
+  if (newlen < buf->size) return;
+
+  if (newlen < buf->offs + buf->size && buf->offs > buf->size / 4) {
+    /* Data fits in the current area, shift it left */
+    memmove(buf->s - buf->offs, buf->s, buf->len + 1);
+    buf->s -= buf->offs;
+    buf->size += buf->offs;
+    buf->offs = 0;
+    return;
+  }
+
+  buf->size = p_alloc_nr(buf->size + buf->offs);
+  if (buf->size < newlen + 1) buf->size = newlen + 1;
+  if (buf->alloced && !buf->offs)
+    p_realloc(&buf->s, buf->size);
+  else {
+    char *new_area = xmalloc(buf->size);
+    memcpy(new_area, buf->s, buf->len + 1);
+    if (buf->alloced) free(buf->s - buf->offs);
+    buf->alloced = true;
+    buf->s = new_area;
+    buf->offs = 0;
+  }
+}
diff --git a/src/buffer.h b/src/buffer.h
new file mode 100644
index 0000000..fbbe9f9
--- /dev/null
+++ b/src/buffer.h
@@ -0,0 +1,78 @@
+#pragma once
+
+#include <assert.h>
+#include <string.h>
+
+#include "utils.h"
+
+typedef struct buffer_t {
+  char *s;
+  int len, size;
+  unsigned alloced : 1;
+  unsigned offs : 31;
+} buffer_t;
+
+extern char buffer_slop[1];
+
+#define BUFFER_INIT (buffer_t){.s = buffer_slop, .size = 1}
+
+/**
+ * Initialize a buffer.
+ * @param buf A buffer pointer.
+ * @return The same buffer pointer.
+ */
+static inline buffer_t *buffer_init(buffer_t *buf) {
+  *buf = BUFFER_INIT;
+  return buf;
+}
+
+void buffer_ensure(buffer_t *buf, int len);
+
+/**
+ * Add data in the buffer.
+ * @param buf Buffer where to add.
+ * @param pos Position where to add.
+ * @param len Length.
+ * @param data Data to add.
+ * @param dlen Data length.
+ */
+static inline void buffer_splice(buffer_t *buf, int pos, int len,
+                                 const void *data, int dlen) {
+  assert(pos >= 0 && len >= 0 && dlen >= 0);
+
+  if (unlikely(pos > buf->len)) pos = buf->len;
+  if (unlikely(len > buf->len - pos)) len = buf->len - pos;
+  if (pos == 0 && len + buf->offs >= dlen) {
+    buf->offs += len - dlen;
+    buf->s += len - dlen;
+    buf->size -= len - dlen;
+    buf->len -= len - dlen;
+  } else if (len != dlen) {
+    buffer_ensure(buf, buf->len + dlen - len);
+    memmove(buf->s + pos + dlen, buf->s + pos + len, buf->len - pos - len);
+    buf->len += dlen - len;
+    buf->s[buf->len] = '\0';
+  }
+  memcpy(buf->s + pos, data, dlen);
+}
+
+/**
+ * Add data at the end of buffer.
+ * @param buf Buffer where to add.
+ * @param data Data to add.
+ * @param len Data length.
+ */
+static inline void buffer_add(buffer_t *buf, const void *data, int len) {
+  buffer_splice(buf, buf->len, 0, data, len);
+}
+
+#define buffer_addsl(buf, data) buffer_add(buf, data, sizeof(data) - 1);
+
+/**
+ * Add a string to the and of a buffer.
+ * @param buf The buffer where to add.
+ * @param s The string to add.
+ */
+static inline void buffer_adds(buffer_t *buf, const char *s) {
+  buffer_splice(buf, buf->len, 0, s, a_strlen(s));
+}
diff --git a/src/config.h.in b/src/config.h.in
new file mode 100644
index 0000000..58537fe
--- /dev/null
+++ b/src/config.h.in
@@ -0,0 +1,5 @@
+#pragma once
+
+#define APP_NAME "@APP_NAME@"
+
+#cmakedefine HAS_EXECINFO
diff --git a/src/main.c b/src/main.c
index 44e82e2..d7d99b7 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1 +1,86 @@
-int main(int argc, char *argv[]) { return 0; }
+#include <glib-unix.h>
+#include <glib.h>
+#include <glibconfig.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "backtrace.h"
+#include "buffer.h"
+#include "types.h"
+#include "utils.h"
+
+zdwm_t global_state;
+
+/** argv used to run zdwm */
+static char **zdwm_argv;
+
+/** A pipe that is used to asynchronously handle SIGCHLD */
+static int sigchld_pipe[2];
+
+static void zdwm_atexit(bool restart) { global_state.need_restart = restart; }
+
+static void zdwm_restart(void) {
+  zdwm_atexit(true);
+  execvp(zdwm_argv[0], zdwm_argv);
+  fatal("execv() failed: %s", strerror(errno));
+}
+
+static gboolean restart_on_signal(gpointer data) {
+  zdwm_restart();
+  return TRUE;
+}
+
+static gboolean exit_on_signal(gpointer data) {
+  g_main_loop_quit(global_state.loop);
+  return TRUE;
+}
+
+static void signal_fatal(int signal_number) {
+  buffer_t buffer;
+  backtrace_get(&buffer);
+  fatal("signal %d, dumping backtrace\n%s", signal_number, buffer.s);
+}
+
+/* Signal handler for SIGCHLD. Causes reap_children() to be called. */
+static void signal_child(int signum) {
+  assert(signum == SIGCHLD);
+  int res = write(sigchld_pipe[1], " ", 1);
+  (void)res;
+  assert(res == 1);
+}
+
+int main(int argc, char *argv[]) {
+  p_clear(&global_state, 1);
+
+  zdwm_argv = argv;
+
+  g_unix_signal_add(SIGINT, exit_on_signal, NULL);
+  g_unix_signal_add(SIGTERM, exit_on_signal, NULL);
+  g_unix_signal_add(SIGHUP, restart_on_signal, NULL);
+
+  struct sigaction sa = {.sa_handler = signal_fatal, .sa_flags = SA_RESETHAND};
+  sigemptyset(&sa.sa_mask);
+  sigaction(SIGABRT, &sa, 0);
+  sigaction(SIGBUS, &sa, 0);
+  sigaction(SIGFPE, &sa, 0);
+  sigaction(SIGILL, &sa, 0);
+  sigaction(SIGSEGV, &sa, 0);
+  signal(SIGPIPE, SIG_IGN);
+
+  sa.sa_handler = signal_child;
+  sa.sa_flags = SA_NOCLDSTOP | SA_RESTART;
+  sigaction(SIGCHLD, &sa, 0);
+
+  if (global_state.loop == NULL) {
+    global_state.loop = g_main_loop_new(NULL, FALSE);
+    g_main_loop_run(global_state.loop);
+  }
+  g_main_loop_unref(global_state.loop);
+  global_state.loop = NULL;
+
+  zdwm_atexit(false);
+
+  return EXIT_SUCCESS;
+}
diff --git a/src/types.h b/src/types.h
new file mode 100644
index 0000000..c9f2742
--- /dev/null
+++ b/src/types.h
@@ -0,0 +1,8 @@
+#pragma once
+
+#include <glib.h>
+
+typedef struct zdwm_t {
+  bool need_restart;
+  GMainLoop *loop;
+} zdwm_t;
diff --git a/src/utils.c b/src/utils.c
new file mode 100644
index 0000000..ece8992
--- /dev/null
+++ b/src/utils.c
@@ -0,0 +1,34 @@
+#include "utils.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include "config.h"
+
+const char *current_time_str(void) {
+  static char buffer[25];
+  time_t now;
+  struct tm tm;
+
+  time(&now);
+  localtime_r(&now, &tm);
+  if (!strftime(buffer, sizeof(buffer), "%Y-%m-%d %T", &tm)) buffer[0] = '\0';
+
+  return buffer;
+}
+
+/** Print error and exit with EXIT_FAILURE code.
+ */
+void _fatal(int line, const char *fct, const char *file, const char *fmt, ...) {
+  va_list ap;
+
+  va_start(ap, fmt);
+  const char *format = "(EE) [%s] %s\n%s:%d:%s:\n";
+  fprintf(stderr, format, APP_NAME, current_time_str(), file, line, fct);
+  vfprintf(stderr, fmt, ap);
+  va_end(ap);
+  fprintf(stderr, "\n");
+  exit(EXIT_FAILURE);
+}
diff --git a/src/utils.h b/src/utils.h
new file mode 100644
index 0000000..8050922
--- /dev/null
+++ b/src/utils.h
@@ -0,0 +1,66 @@
+#pragma once
+
+#include <stdlib.h>
+#include <string.h>
+
+#define ssizeof(foo) (ssize_t)sizeof(foo)
+#define countof(foo) (ssizeof(foo) / ssizeof(foo[0]))
+
+#define p_alloc_nr(x) (((x) + 16) * 3 / 2)
+#define p_clear(p, count) ((void)memset((p), 0, sizeof(*(p)) * (count)))
+#define p_realloc(pp, count) xrealloc((void *)(pp), sizeof(**(pp)) * (count))
+
+#define p_delete(mem_p)              \
+  do {                               \
+    void **__ptr = (void **)(mem_p); \
+    free(*__ptr);                    \
+    *(void **)__ptr = NULL;          \
+  } while (0)
+
+#ifdef __GNUC__
+#define likely(expr) __builtin_expect(!!(expr), 1)
+#define unlikely(expr) __builtin_expect((expr), 0)
+#else
+#define likely(expr) expr
+#define unlikely(expr) expr
+#endif
+
+static inline void *__attribute__((malloc)) xmalloc(ssize_t size) {
+  void *ptr;
+
+  if (size <= 0) return NULL;
+
+  ptr = calloc(1, size);
+
+  if (!ptr) abort();
+
+  return ptr;
+}
+
+static inline void xrealloc(void **ptr, ssize_t newsize) {
+  if (newsize <= 0)
+    p_delete(ptr);
+  else {
+    *ptr = realloc(*ptr, newsize);
+    if (!*ptr) abort();
+  }
+}
+
+/**
+ * @brief NULL resistant strlen.
+ *
+ * Unlike it's libc sibling, a_strlen returns a ssize_t, and supports its
+ * argument being NULL.
+ *
+ * @param s the string.
+ * @return the string length (or 0 if s is NULL).
+ */
+static inline ssize_t a_strlen(const char *s) { return s ? strlen(s) : 0; }
+
+#define fatal(format, ...) \
+  _fatal(__LINE__, __FUNCTION__, __FILE__, format, ##__VA_ARGS__)
+void _fatal(int line, const char *function, const char *file,
+            const char *format, ...) __attribute__((noreturn))
+__attribute__((format(printf, 4, 5)));
+
+const char *current_time_str(void);