Access to member variable by 'friend'

[Morten Aune Lyrstad]

I am in the process of writing a virtual machine. I know that one should
not give access to private variables in a class (by using friend) but
wouldn't that speed up execution? Like this:

class Script;

class Instruction
{
...
private
int someCode;
friend Script;
}

class Script
{
...
void Execute(...)
{
switch (currentScript.someCode) {
... ... ...


rather than using a function by the name GetCode or whatever? Or is
there some other reason why this should not be done? As long as the user
of these scripts don't get access to those variables, everything should
be ok, right?

Yours,
Morten Aune Lyrstad

 

[Krishanu Debnath]

I am in the process of writing a virtual machine. I know that one
should not give access to private variables in a class (by using
friend) but wouldn't that speed up execution? Like this:

Why don't you use inline member_access function?

Krishanu

 

[Morten Aune Lyrstad]

Morten Aune Lyrstad wrote:



Why don't you use inline member_access function?

Krishanu

Won't you still get function call overhead, or will the compiler
understand what I want and make a simple assignment?

 

[Karl Heinz Buchegger]

Won't you still get function call overhead, or will the compiler
understand what I want and make a simple assignment?

You worry to much.
Exactly that was the intent in 'inline' functions: To get rid of
the call overhead.
While the compiler is free to ignore your hint, it is unlikely
that it does so in such simple cases: Such a compiler would not
sell or not be used in practice.

 

[Morten Aune Lyrstad]

Ok; thank you for clearing that up for me!

 

[Micah Cowan]

I am in the process of writing a virtual machine. I know that one should
not give access to private variables in a class (by using friend) but
wouldn't that speed up execution? Like this:

class Script;

class Instruction
{
...
private
int someCode;
friend Script;
}

class Script
{
...
void Execute(...)
{
switch (currentScript.someCode) {
... ... ...


rather than using a function by the name GetCode or whatever? Or is
there some other reason why this should not be done? As long as the user
of these scripts don't get access to those variables, everything should
be ok, right?

A function such as GetCode() could easily be written as an inline
function member, in which case speed would not be an issue, on
any decent implementation.