i2l | Portable I2L interpreter in C | Interpreter library

Anything inside your if(!IsPostBack) condition will only be executed on initial load and not on submit. You could put the code you want to run on submit (postback) inside an else if you want

msg should be like this

It was my bad. I just had to update "Angular", "Nativescript" and "tns-core-modules" to the latest version.

First of all, you have a misunderstanding of the purpose of stack map frames. These frames have to be inserted at branch merge points to declare the stack frame state right at this point. Since your constructor doesn’t contain branches, there is no need to insert any frame at all. Further, your declaration of two local variables and two operand stack entries doesn’t match the actual situation at any point in the constructor.

But ASM’s COMPUTE_FRAMES also implies (re-)calculating the max values for local variables and the operand stack. The problem of your code is that you still have to invoke the associated visitMaxs method, even if the arguments are not used, to indicate to ASM that you’re done with the code and the values need to be calculated. I use -1 as arguments here, to make it pretty clear that the arguments are not the actual values, but ASM is expected to recalculate them:

The given fragment is incomplete. The actual allocation code should be right above this fragment.

mov %r12d,0xc(%rsi) is the last instruction of allocation sequence - it just zeroes the last padding word of the new object.

I've already decribed how object allocation works in HotSpot in this, this and this answers. You won't see any syscalls there since JVM does not rely on system allocator. It uses its own memory management in the preallocated region - Java Heap.

Here is how allocation sequence typically looks like in C2-compiled code. The comments are mine.

The local variables, as reported by visitLocalVariable, are only debug information, as stored in the LocalVariableTable attribute and LocalVariableTypeTable attribute. If these attributes are not present, no such declarations will be reported.

Further, they are not required to be complete regarding bytecode level variables, i.e. they do not report the second variable occupied by long and double values. They also may not include synthetic variables, like introduced by the for-each construct (holding the hidden iterator), try-with-resource construct (holding pending exceptions) or pending values like in
try { return expression; } finally { otherAction(); } constructs.

On the bytecode level, local variables are established by actually storing values into them (referring to the index only). Variables having disjunct scopes on the source code level may use the same index in the stack frame. To the bytecode, it doesn’t matter whether two writes to the same index are actually a change of the same variable or two variables with different scope. But the sizes as reported by visitMaxs must be large enough to hold the operand stack elements and all variable indices used in the method’s stack frame. Also stack map table frames are mandatory for new class files specifying the expected types for branch targets.

Since ASM reports the old max locals at the end of the visiting, you can’t use that to use indices larger than that beforehand, but it’s not necessary. As said above, variable indices are not required to be unique. Your use case is like introducing a new variable scope, so you may use indices that haven’t been used before that point and there is no problem if these indices are used again by subsequent code after your injected code ended.

Getting the indices which have been used before a certain point is not so hard, if you can live with only supporting newer class files having StackMapTable attributes. For these classes you only have to care for two events. At branch targets, visitFrame will report which variables are in use at this point. Using this information is easier when specifying EXPAND_FRAMES to the ClassReader. The other event to care are actual variable use instructions (actually, only stores matter), which are reported via visitVarInsn. Putting it together, the sketch looks like