Unable to calc the 'sizeof' of a member of struct (pointers problem?)

I have this 2 functions

myfunction1 (myclass &value)
myfunction2 (int &value)

I want to pass the values by ref to avoid copies.
Ok, I have a object created like this
a_struc * my_struc= new a_struc;
(a_struc is a simple struct with 3 fields, the third is an int field called a3. )

myfunction1(*mystruc) works
myfunction2(*mystruc->a3) does not compile
myfunction2(mystruc->a3) compile, but inside myfunction2 I have :
int si = sizeof value; and in this last case I have an error ....(programs crash)

Any help? Thanks

Quote:

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I want to pass the values by ref to avoid copies.

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Passing an int by reference is not going to give you some incredible increase in app performance :P
btw if arguments are meant to be read-only, pass them by const reference ( for classes and structs ) or value (ints, doubles etc )

Quote:

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myfunction2(*mystruc->a3) does not compile

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Correct syntax would be myfunction2(mystruc->a3) or myfunction2((*mystruc).a3), but I think you've already figured it out.

Quote:

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but inside myfunction2 I have :
int si = sizeof value; and in this last case I have an error ....(programs crash)

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Make sure pointer is not deleted before function call, this works ok:

Code:

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#include <iostream>
 
struct my_struct{
	int x, y, z;
};
void method( int x ){ // or by reference int &x, works as well
	std::cout << sizeof x << "\n";
}
void method( const my_struct& s ){
	std::cout << sizeof(s) << "\n";
}
int main( int argc, char ** argv ){
	my_struct * s = new my_struct;
	method((*s).x);
	method(s->x);
	method(*s);
	delete s;
	return 0;
}

---

In myfunction1 and 2 value is a reference to myclass and integer so sizeof returns 4 for 32bit or 8 for 64bit

This code

Code:

---

#include <QCoreApplication>
 
struct MyStruct
{
    int a3;
};
 
void myfunction1 (MyStruct &value)
{
    int si = sizeof (value);
 
    qDebug ("[%s]: Sizeof = %d", Q_FUNC_INFO, si);
}
 
void myfunction2 (int &value)
{
    int si = sizeof (value);
 
    qDebug ("[%s]: Sizeof = %d", Q_FUNC_INFO, si);
}
 
int main (int argc, char* argv[])
{
    QCoreApplication a (argc, argv);
 
    qDebug ("Hello World");
 
    MyStruct *ms = new MyStruct;
 
    myfunction1 (*ms);
 
    myfunction2 (ms->a3);
 
    delete ms;
}

---

executes without crash with output

Code:

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Hello World
[void myfunction1(MyStruct&)]: Sizeof = 4
[void myfunction2(int&)]: Sizeof = 4

---

I'm going to stop ....
I hope to solve this tomorrow ...
There is something strange, I dont know where is the problem but code that works fine (as the examples you have showed) does not work into my classes ...
Thanks in any way.

sizeof() is often implemented as a macro, and requires parentheses around the argument. Your psuedo-code doesn't do this; if your code doesn't, that's likely the problem.

post you code