debug_class_file: add Exceptions attribute printing

c/class_file.c

@@ -90,6 +90,15 @@ void * attribute_info_parse_info(const uint8_t * buf, struct attribute_info * at
       line_number_table->line_number_table[i].line_number = parse_u2(&buf);
     }
     return line_number_table;
+  } else if (constant_equal(attribute_name, "Exceptions")) {
+    struct Exceptions_attribute * exceptions = malloc_class_arena((sizeof (struct Exceptions_attribute)));
+    exceptions->number_of_exceptions = parse_u2(&buf);
+    uint32_t exceptions_size = (sizeof (u2)) * exceptions->number_of_exceptions;
+    exceptions->exception_index_table = malloc_class_arena(exceptions_size);
+    for (int i = 0; i < exceptions->number_of_exceptions; i++) {
+      exceptions->exception_index_table[i] = parse_u2(&buf);
+    }
+    return exceptions;
   } else {
     return nullptr;
   }

c/class_file.h

@@ -136,6 +136,7 @@ struct NestHost_attribute;
 struct NestMembers_attribute;
 struct PermittedSubclasses_attribute;
 struct LineNumberTable_attribute;
+struct Exceptions_attribute;
 
 struct attribute_info {
   u2 attribute_name_index;
@@ -150,6 +151,7 @@ struct attribute_info {
     struct NestMembers_attribute * nestmembers;
     //struct PermittedSubclasses_attribute * permittedsubclasses;
     struct LineNumberTable_attribute * line_number_table;
+    struct Exceptions_attribute * exceptions;
   };
 };
 
@@ -205,6 +207,11 @@ struct LineNumberTable_attribute {
   struct line_number_table * line_number_table;
 };
 
+struct Exceptions_attribute {
+  u2 number_of_exceptions;
+  u2 * exception_index_table;
+};
+
 enum FIELD_ACC {
   FIELD_ACC_PUBLIC    = 0x0001, // Declared public; may be accessed from outside its package.
   FIELD_ACC_PRIVATE   = 0x0002, // Declared private; accessible only within the defining class and other classes belonging to the same nest (§5.4.4).

c/debug_class_file.c

@@ -224,6 +224,28 @@ static void print_line_number_table(const char * indent, struct attribute_info *
   }
 }
 
+static void print_exceptions(const char * indent, struct attribute_info * attribute, struct constant * constant_pool)
+{
+  prints(indent);
+  printf("number_of_exceptions: %d\n", attribute->exceptions->number_of_exceptions);
+  prints(indent);
+  printf("exceptions:\n");
+  for (int i = 0; i < attribute->exceptions->number_of_exceptions; i++) {
+    prints(indent);
+    printf("  exception_index_table[%d]: %d\n", i, attribute->exceptions->exception_index_table[i]);
+    struct constant * class_constant = &constant_pool[attribute->exceptions->exception_index_table[i] - 1];
+    assert(class_constant->tag == CONSTANT_Class);
+    prints(indent);
+    prints("    ");
+    print_constant(class_constant);
+    struct constant * class_name_constant = &constant_pool[class_constant->class.name_index - 1];
+    assert(class_name_constant->tag == CONSTANT_Utf8);
+    prints(indent);
+    prints("      ");
+    print_constant(class_name_constant);
+  }
+}
+
 static void print_attribute(const char * indent, struct attribute_info * attribute, struct constant * constant_pool)
 {
   prints(indent);
@@ -245,6 +267,8 @@ static void print_attribute(const char * indent, struct attribute_info * attribu
     print_nestmembers(indent, attribute, constant_pool);
   } else if (constant_equal(attribute_name, "LineNumberTable")) {
     print_line_number_table(indent, attribute, constant_pool);
+  } else if (constant_equal(attribute_name, "Exceptions")) {
+    print_exceptions(indent, attribute, constant_pool);
   }
 }
 

java/lang/Throwable.java

@@ -20,4 +20,8 @@ public class Throwable {
     public Throwable(Throwable cause) {
         this.cause = cause;
     }
+
+    public String toString() {
+        return message;
+    }
 }

p/TestException.java

@@ -1,8 +1,16 @@
 package p;
 
 class TestException {
+    static void test2() throws Exception {
+        throw new Exception("asdf exception");
+    }
+
     static void test() throws Exception {
-        throw new Exception("asdf");
+        try {
+            test2();
+        } catch (Exception e) {
+            System.out.println(e);
+        }
     }
 
     public static void main() throws Exception {