Delphi call JNI methods with variable argument list

Question

Using Embarcadero\'s Jni api unit, how does one supply variable argument lists to the JNI methods that require it? For example, the CallStaticObjectMethodV() method of the JNINa

Answer 1

The va_list needs to point to a block of memory that matches what would be pushed onto the stack if you had instead called a variadic function.

The usual implementation of va_start simply yields the address of the location on the stack where the variadic arguments were pushed.

#define va_start(ap, parmN) ((void)((ap) = (va_list)((char _FAR *)(&parmN)+__size(parmN)))) 

So your attempt to make an array containing the arguments, and use that as your va_list ought to work. Perhaps you've given up on it too hastily? Perhaps instead of:

Move( Str1, Data[0], Sz);
Move( Str1, Data[Sz], Sz);

you meant

Move( Str1, Data[0], Sz);
Move( Str2, Data[Sz], Sz);

Although personally I'd opt for a array of JNIString rather than a byte array.

So perhaps your approach to create the va_list is fine, but the failure is caused by an error elsewhere.