--- a/src/cospy.c	Wed Sep 08 22:16:25 2010 +0800
+++ b/src/cospy.c	Thu Sep 09 08:20:15 2010 +0800
@@ -8,10 +8,19 @@
 #include "cgraph.h"
 #include <stdio.h>
 
+/* This is required for GCC plugin, or it is can not be loaded */
 int plugin_is_GPL_compatible;
 
 /*! \brief Parse a tree of type and return respective string.
  *
+ * The struncture of a pointer type
+ *  - pointer:pointer_type
+ *    - type:*_type
+ *      - name:type_decl
+ *        - name:identifier
+ *
+ * For a constant type, it is flaged as a readonly.
+ *
  * \return a string for the type.  It must be free through ggc_free().
  */
 static char *
@@ -19,12 +28,12 @@
     tree type_v;
     tree *pointers;
     tree type_decl, type_name;
-    int lvl = 0;
+    int ptr_lvl = 0;
     int const_cnt = 0;
     char *type_str;
     const char *base_type_name;
     int type_str_len;
-    int i, ptr_i;
+    int str_i, ptr_i;
     
     /* Collect pointers */
     type_v = type_node;
@@ -32,12 +41,12 @@
 	if(TREE_READONLY(type_v))
 	    const_cnt++;
 	type_v = TREE_TYPE(type_v);
-	lvl++;
+	ptr_lvl++;
     }
 
-    pointers = (tree *)ggc_alloc(sizeof(tree) * lvl);
+    pointers = (tree *)ggc_alloc(sizeof(tree) * ptr_lvl);
     type_v = type_node;
-    for(ptr_i = 0; ptr_i < lvl; ptr_i++) {
+    for(ptr_i = 0; ptr_i < ptr_lvl; ptr_i++) {
 	pointers[ptr_i] = type_v;
 	type_v = TREE_TYPE(type_v);
     }
@@ -48,29 +57,29 @@
     base_type_name = IDENTIFIER_POINTER(type_name);
     
     /* Compute total length of string of full type */
-    type_str_len = lvl + strlen(base_type_name) + const_cnt * 5; /* "const" */
+    type_str_len = ptr_lvl + strlen(base_type_name) +
+	const_cnt * 5;		/* "const" */
     if(TREE_READONLY(type_v))
 	type_str_len += 6;	/* "const " */
     type_str = (char *)ggc_alloc(type_str_len + 1);
     
-    /* modify const for base type */
+    /* base type and constant modification */
     type_str[0] = 0;
     if(TREE_READONLY(type_v))
 	strcpy(type_str, "const ");
     strcat(type_str, base_type_name);
     
     /* Add pointers and const modifications after base type */
-    i = strlen(type_str);
-    for(ptr_i = lvl - 1; ptr_i >= 0; ptr_i--) {
+    str_i = strlen(type_str);
+    for(ptr_i = ptr_lvl - 1; ptr_i >= 0; ptr_i--) {
 	type_v = pointers[ptr_i];
-	type_str[i++] = '*';
+	type_str[str_i++] = '*';
 	if(TREE_READONLY(type_v)) {
-	    type_str[i] = 0;
-	    strcat(type_str, "const");
-	    i += 5;
+	    strcpy(type_str + str_i, "const");
+	    str_i += 5;
 	}
     }
-    type_str[i] = 0;
+    type_str[str_i] = 0;
     
     ggc_free(pointers);
 
@@ -100,6 +109,13 @@
     }
 }
 
+/*! \brief This function is called before running all_passes.
+ *
+ * all_passes is a list of optimization passes of GCC.  See
+ * init_optimization_passes() in gcc/passes.c of GCC.
+ *
+ * This function is called for every function.
+ */
 static void
 handle_all_passes(void *gcc_data, void *user_data) {
     tree decl;
@@ -110,16 +126,32 @@
     char *arg_type_str;
     function_args_iterator itr;
     
+    /*
+     * GCC uses cgraph_node to save information of functions and
+     * relationships between functions (a.k.a call graphy).
+     */
     decl = cfun->decl;
     cgn = cgraph_node(decl);
      
     printf("%s:%d:%s\n", current_function_name(),
 	   DECL_SOURCE_LINE(decl),
 	   DECL_SOURCE_FILE(decl));
+    
     show_callees(cgn);
     
+    /*
+     * Parse and show arguments of the function.
+     */
     arg = DECL_ARGUMENTS(decl);
     while(arg) {
+	/*
+	 * The structure of an argument.
+	 * - parm
+	 *   - name:identifier
+	 *   - type:type
+	 *     - name:type_decl
+	 *       - name:identifier
+	 */
 	arg_name = DECL_NAME(arg);
 	arg_type = TREE_TYPE(arg);
 	arg_type_str = parse_type(arg_type);
@@ -131,6 +163,8 @@
     }
 }
 
+/*! \brief Initialize function for the plugin.
+ */
 int
 plugin_init(struct plugin_name_args *plugin_info,
 	    struct plugin_gcc_version *version) {
@@ -140,6 +174,9 @@
 	return 1;
     printf("Initialize plugin %s\n", plugin_info->base_name);
 
+    /*
+     * Register a callback called before running passes in all_passes.
+     */
     register_callback(plugin_info->base_name, PLUGIN_ALL_PASSES_START,
 		      handle_all_passes, NULL);
     return 0;