[feature] local variable size

lvntky · Jun 23, 2024 · bc16072 · bc16072
1 parent e03ee8b
commit bc16072
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diff --git a/sample/javap_AddMain.txt b/sample/javap_AddMain.txt
@@ -356,3 +356,63 @@ Constant pool:
         line 7: 10
 }
 SourceFile: "AddMain.java"
+Classfile /home/levent/Projects/CVM/sample/AddMain.class
+  Last modified Jun 22, 2024; size 282 bytes
+  SHA-256 checksum 686603e16d220775966c2568e490983b83c5b5e5725340e919941eec59436e23
+  Compiled from "AddMain.java"
+class AddMain
+  minor version: 0
+  major version: 66
+  flags: (0x0020) ACC_SUPER
+  this_class: #7                          // AddMain
+  super_class: #2                         // java/lang/Object
+  interfaces: 0, fields: 0, methods: 2, attributes: 1
+Constant pool:
+   #1 = Methodref          #2.#3          // java/lang/Object."<init>":()V
+   #2 = Class              #4             // java/lang/Object
+   #3 = NameAndType        #5:#6          // "<init>":()V
+   #4 = Utf8               java/lang/Object
+   #5 = Utf8               <init>
+   #6 = Utf8               ()V
+   #7 = Class              #8             // AddMain
+   #8 = Utf8               AddMain
+   #9 = Utf8               Code
+  #10 = Utf8               LineNumberTable
+  #11 = Utf8               main
+  #12 = Utf8               ([Ljava/lang/String;)I
+  #13 = Utf8               SourceFile
+  #14 = Utf8               AddMain.java
+{
+  AddMain();
+    descriptor: ()V
+    flags: (0x0000)
+    Code:
+      stack=1, locals=1, args_size=1
+         0: aload_0
+         1: invokespecial #1                  // Method java/lang/Object."<init>":()V
+         4: return
+      LineNumberTable:
+        line 1: 0
+
+  public static int main(java.lang.String[]);
+    descriptor: ([Ljava/lang/String;)I
+    flags: (0x0009) ACC_PUBLIC, ACC_STATIC
+    Code:
+      stack=2, locals=4, args_size=1
+         0: bipush        14
+         2: istore_1
+         3: bipush        15
+         5: istore_2
+         6: iload_1
+         7: iload_2
+         8: iadd
+         9: istore_3
+        10: iload_3
+        11: ireturn
+      LineNumberTable:
+        line 4: 0
+        line 5: 3
+        line 6: 6
+        line 7: 10
+}
+SourceFile: "AddMain.java"
diff --git a/src/execute_engine/cvm_execute.cpp b/src/execute_engine/cvm_execute.cpp
@@ -4,6 +4,7 @@
 
 // Temporarily store codeLength globally
 size_t codeLength = 0;
+size_t maxLocals = 0;
 
 /**
  * Helper methods
@@ -101,6 +102,9 @@ const uint8_t* CVM::getByteCode(const Classfile& cf,
       codeLength = attr.attribute_length;
       spdlog::info("code length: {}, The attribute name index: {:#x}",
                    codeLength, attr.attribute_name_index);
+      maxLocals = (attr.info[2] << 8) |
+                  attr.info[3];  // max_locals is a 2-byte value at offset 2
+      spdlog::info("maxLocals = {}", maxLocals);
       return attr.info;
     }
   }