On May 20, 4:01 pm, "Thomas J. Gritzan" <phygon_antis...@gmx.de>
darren wrote:
On May 20, 12:37 pm, Martin York <Martin.YorkAma...@gmail.com> wrote:
[...]
If the result had been returned by reference then you would encounter
problems.
cool, thanks for the helpful info Martin. I didn't know that
returning an object makes a copy of the object to pass back. What
would happen if you returned a reference to an object? If it
referenced something local, would the reference but null since that
stackframe is destroyed?
int& reftoInt()
{
int i = 5;
return i; // don't do this!
}
i is an automatic variable that gets invalid when leaving the function,
so you return a reference to a lost object. Bad idea!
int& reftoStaticInt()
{
static int i = 5;
return i; // ok
}
A static variable has 'infinite' lifetime, you can pass a pointer or
reference to it around and can access it until the program ends.
int copyOfInt()
{
int i = 5;
return i; // ok, too
}
Since the return type is not a reference but normal object, the value
(5) will be copied before the local variable will be destroyed.
Also, say i had a statement like this:
char* myCString = "a string"
string myCppString = "another string"
A _string literal_ like "yet another string literal" has 'infinite'
lifetime (= lives until the program ends) just like a static variable.
const char* string1 = "a string";
This is a pointer to a string literal. Its valid until the program ends.
char string2[] = "a string";
This is a character array, initialized from a string literal (the
contents will be copied to the array). Defined in a function, it has
automatic lifetime (until end of function) and returning a pointer to
this array is a bad idea, since the pointer will point to invalid memory.
std::string string3 = "a string";
This is an object of class std::string. Just like string2, it is
initialized from a string literal. When defined locally in a function,
it will be destroyed on its end just like the char array, so returning a
pointer or reference to it is a bad idea, too. But you can return a full
object, so the string will be copied.
I'm assuming that these string literals are stored on the heap? If so,
do i need to explicitly manage that memory? I thought I read that C++
handles those types of object automatically, but i"m not sure.
Victor: as for why its main(void), i copied some code created by the
Eclipse CDT C++ tool.
int main(void) is idiomatic in C but discuraged (because unnecessary) in
C++.
--
Thomas
thomas, that saved me a lot of reading and searching for answers.