java - Operand stack underrun -

-

i have program generate bytecode java file. , simple test() method

public void test() {     boolean = false;     if (a || true)     {          boolean b = false;     } }

, generate follow piece of bytecode

public void test()   code:    7:   iconst_0    8:   istore_1    9:   iload_1    10:  ifne    13    13:  iconst_0    14:  istore_2    15:  return

when execute class, keep getting operand stack underrun in test(), couldn't figure out why because generated bytecode looks (to me)

could me debug this?

(here's did trace stack

public void test()   code:    7:   iconst_0  (1 on stack)    8:   istore_1  (0 on stack)    9:   iload_1  (1 on stack)    10:  ifne    13  (0 on stack)    13:  iconst_0  (1 on stack)    14:  istore_2  (0 on stack)    15:  return

so yeah, stack looks fine me!)

edit: here's generated bytecode javac

public void test();   code:    0:   iconst_0    1:   istore_1    2:   iload_1    3:   ifne    6    6:   iconst_0    7:   istore_2    8:   return

when try this

public class maindump implements opcodes {      public static byte[] dump() throws exception {          classwriter cw = new classwriter(0);         fieldvisitor fv;         methodvisitor mv;         annotationvisitor av0;          cw.visit(v1_7, acc_public + acc_super, "main", null, "java/lang/object", null);          cw.visitsource("main.java", null);          {             mv = cw.visitmethod(acc_public, "<init>", "()v", null, null);             mv.visitcode();             label l0 = new label();             mv.visitlabel(l0);             mv.visitlinenumber(1, l0);             mv.visitvarinsn(aload, 0);             mv.visitmethodinsn(invokespecial, "java/lang/object", "<init>", "()v");             mv.visitinsn(return);             label l1 = new label();             mv.visitlabel(l1);             mv.visitlocalvariable("this", "lmain;", null, l0, l1, 0);             mv.visitmaxs(1, 1);             mv.visitend();         }         {             mv = cw.visitmethod(acc_public, "test", "()v", null, null);             mv.visitcode();             mv.visitinsn(iconst_0);             mv.visitvarinsn(istore, 1);             mv.visitvarinsn(iload, 1);             label l2 = new label();             mv.visitjumpinsn(ifeq, l2);             mv.visitinsn(iconst_0);             mv.visitvarinsn(istore, 2);             mv.visitlabel(l2);             mv.visitframe(opcodes.f_append, 1, new object[]{opcodes.integer}, 0, null);             mv.visitinsn(return);             mv.visitmaxs(1, 3);             mv.visitend();         }         cw.visitend();          return cw.tobytearray();     }      public static void main(string... ignored) throws exception {         method defineclass = classloader.class.getdeclaredmethod("defineclass", byte[].class, int.class, int.class);         defineclass.setaccessible(true);          byte[] dump = dump();         defineclass.invoke(thread.currentthread().getcontextclassloader(), dump, 0, dump.length);         new main().test();     } }

this works, if drop stack frame adjustment, error

exception in thread "main" java.lang.verifyerror: expecting stackmap frame @ branch target 8 exception details:   location:     main.test()v @3: ifeq   reason:     expected stackmap frame @ location.   bytecode:     0000000: 033c 1b99 0005 033d b1

in short, java 7, stack operations not enough pass validity.


Comments

Post a Comment

Popular posts from this blog

c# - How Configure Devart dotConnect for SQLite Code First? -

-
can configure following sample code ? when run following code, error : no entity framework provider found ado.net provider invariant name 'devart.data.sqlite' setting in machine.config <system.data> <dbproviderfactories> <add name="dotconnect sqlite" invariant="devart.data.sqlite" description="devart dotconnect sqlite" type="devart.data.sqlite.sqliteproviderfactory, devart.data.sqlite, version=4.6.287.0, culture=neutral, publickeytoken=09af7300eec23701" /> </dbproviderfactories> </system.data> after add below block code in app.config <?xml version="1.0"?> <configuration>   <configsections> <!-- more information on entity framework configuration, visit http://go.microsoft.com/fwlink/?linkid=237468 --> <section name="entityframework" type="system.data.entity.internal.configfile.entityframeworksection, entit...
Read more

c++ - Clear the memory after returning a vector in a function -

-
i have function processes , stores lot of data in , returns results vector of class. amount of data stored in function tremendous , want clear storage memory of function after finished job. necessary (does function automatically clear memory) or should clear memory function? update: vector<customers> process(char* const *filename, vector<int> id) { vector<customers> list_of_customers; (perform actions) return list_of_customers; } variables defined locally within function automatically released @ end of function scope. destructors objects called, should free memory allocated objects (if objects coded correctly). example of such object std::vector . anything you've allocated new must have corresponding delete release storage. try avoid doing own allocation , use raii instead, i.e. containers or smart pointers.
Read more

erlang - Saving a digraph to mnesia is hindered because of its side-effects -

-
updated the digraph library in erlang implements data type side-effectful. each operation on data type saves new state in ets table -- instead of returning altered version of itself, more common in functional languages. the problem usage perspective, impedes effort store or pass around state in convenient way requiring me first "collect" state before can start juggle around. the closest solution have seen far serializer/deserializer , these have drawback tied current structure of digraphs instead of operating on abstract type -- prevents future proof solution. update pascal pointed out serializer utilizes interface of digraph, , hence eliminates drawback mentioned above. better, albeit still inconvenient, see no better alternative. what recommendation on how store digraphs? should go different data type altogether? thanks. i not sure understand concern. fact digraph stored in ets transparent in user interface, might want chnge either exchange digr...
Read more