diff --git a/cii/CMakeLists.txt b/cii/CMakeLists.txt
index 8ad9a63d..e9a3fb4e 100644
--- a/cii/CMakeLists.txt
+++ b/cii/CMakeLists.txt
@@ -5,10 +5,12 @@ set(CMAKE_C_STANDARD 11)
 
 set(SOURCE_FILES
     src/atom.c
+    src/except.c
     src/hash.c
     )
 set(HEADER_FILES
     include/cii/atom.h
+    include/cii/except.h
     include/cii/hash.h
     )
 
diff --git a/cii/include/cii/except.h b/cii/include/cii/except.h
new file mode 100644
index 00000000..d1893b11
--- /dev/null
+++ b/cii/include/cii/except.h
@@ -0,0 +1,96 @@
+// Copyright (c) 2023 Xu Shaohua <shaohua@biofan.org>. All rights reserved.
+// Use of this source is governed by GNU General Public License
+// that can be found in the LICENSE file.
+
+#ifndef CII_EXCEPT_H_
+#define CII_EXCEPT_H_
+
+#include <setjmp.h>
+
+struct except_s {
+  int type;
+  const char* reason;
+};
+
+typedef struct except_s except_t;
+
+struct except_frame_s {
+  struct except_frame_s* prev;
+  jmp_buf env;
+  const char* file;
+  int line;
+  const except_t* exception;
+};
+
+typedef struct except_frame_s except_frame_t;
+
+// Global exception stack frame.
+extern except_frame_t* g_except_stack;
+
+enum except_state_e {
+  except_state_entered = 0,
+  except_state_raised,
+  except_state_handled,
+  except_state_finalized,
+};
+
+/**
+ * It is a checked runtime error if e is null.
+ *
+ * @param e is a pointer to global or static except_t instance.
+ * @param file source file name where exception occurs.
+ * @param line line number where exception occurs.
+ */
+void except_raise(const except_t* e, const char* file, int line);
+
+#define RAISE(e) except_raise(&(e), __FILE__, __LINE__)
+
+#define REREAISE \
+  except_raise(except_frame.exception, except_frame.file, except_frame.line)
+
+#define RETURN switch(0) default: return
+
+#define TRY                                    \
+do {                                           \
+  volatile except_state_e except_flag;         \
+  except_frame_t except_frame;                 \
+  except_frame.prev = g_except_stack;          \
+  g_except_stack = &except_frame;              \
+  except_flag = setjmp(except_frame.env);      \
+  if (except_flag == except_state_entered) {   \
+
+#define EXCEPT(e)                              \
+    if (except_flag == except_state_entered) { \
+      g_except_stack = except_stack->prev;     \
+    }                                          \
+  } else if (except_frame.exception == &(e)) { \
+    except_flag = except_state_handled;
+
+#define ELSE                                   \
+    if (except_flag == except_state_entered) { \
+      g_except_stack = except_stack->prev;     \
+    }                                          \
+  } else {                                     \
+    except_flag = except_state_handled;
+
+#define FINALLY                                \
+    if (except_flag == except_state_entered) { \
+      g_except_stack = except_stack->prev;     \
+    }                                          \
+  }                                            \
+  {                                            \
+    if (except_flag == except_state_entered) { \
+      except_flag = except_state_finalized;    \
+    }
+
+#define END_TRY                                \
+    if (except_flag == except_state_entered) { \
+      g_except_stack = except_stack->prev;     \
+    }                                          \
+  }                                            \
+  if (except_flag == except_raised) {          \
+    RERAISE;                                   \
+  }                                            \
+} while (0)
+
+#endif  // CII_EXCEPT_H_
diff --git a/cii/include/cii/mem.h b/cii/include/cii/mem.h
new file mode 100644
index 00000000..16b7f2e1
--- /dev/null
+++ b/cii/include/cii/mem.h
@@ -0,0 +1,16 @@
+// Copyright (c) 2023 Xu Shaohua <shaohua@biofan.org>. All rights reserved.
+// Use of this source is governed by GNU General Public License
+// that can be found in the LICENSE file.
+
+#ifndef CII_MEM_H_
+#define CII_MEM_H_
+
+#include <stddef.h>
+
+extern const except_t mem_failed;
+
+void* mem_alloc(size_t nbytes, const char* file, int line);
+
+void* mem_calloc(size_t count, size_t nbytes, const char* file, int line);
+
+#endif  // CII_MEM_H_
diff --git a/cii/src/except.c b/cii/src/except.c
new file mode 100644
index 00000000..f966555a
--- /dev/null
+++ b/cii/src/except.c
@@ -0,0 +1,42 @@
+// Copyright (c) 2023 Xu Shaohua <shaohua@biofan.org>. All rights reserved.
+// Use of this source is governed by GNU General Public License
+// that can be found in the LICENSE file.
+
+#include "cii/except.h"
+
+#include <assert.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+except_frame_t* g_except_stack = NULL;
+
+void except_raise(const except_t* e, const char* file, int line) {
+  except_frame_t* frame = g_except_stack;
+  assert(e != NULL);
+
+  if (frame == NULL) {
+    // uncaught exception.
+    fprintf(stderr, "Uncaught exception");
+    if (e->reason != NULL) {
+      fprintf(stderr, " %s", e->reason);
+    } else {
+      fprintf(stderr, " at 0x%p", e);
+    }
+    if (file != NULL && line > 0) {
+      fprintf(stderr, " raised at %s:%d\n", file, line);
+    } else {
+      fprintf(stderr, "\n");
+    }
+    fprintf(stderr, "aborting...\n");
+    fflush(stderr);
+    abort();
+  }
+
+  frame->exception = e;
+  frame->file = file;
+  frame->line = line;
+  // pop except frame.
+  g_except_stack = frame->prev;
+  longjmp(frame->env, except_state_raised);
+}
\ No newline at end of file
diff --git a/cii/src/mem.c b/cii/src/mem.c
new file mode 100644
index 00000000..ea036944
--- /dev/null
+++ b/cii/src/mem.c
@@ -0,0 +1,6 @@
+// Copyright (c) 2023 Xu Shaohua <shaohua@biofan.org>. All rights reserved.
+// Use of this source is governed by GNU General Public License
+// that can be found in the LICENSE file.
+
+#include "cii/mem.h"
+