hi All

the following comes from c++ standards:

"Accessing an object designated by a volatile lvalue (3.10), modifying
an object, calling a library I/O
function, or calling a function that does any of those operations are
all side effects, which are changes in the
state of the execution environment."

According to this definition, consider this function,

T ReturnT(){
T result_;
//do something
return result_; // #1
}

At #1, I think
1) if T is scalre type such as int or char, the returning sentence
would not have side effects
2) if T is a class type, does returning type T have side effects? and
Why? I.e. which program state is changed in the T's copy constrcutor.

Thanks
Chang

On Apr 8, 3:42pm, baibaichen <baibaic...@gmail.com> wrote:
> the following comes from c++ standards:
>
> "Accessing an object designated by a volatile lvalue (3.10), modifying
> an object, calling a library I/O
> function, or calling a function that does any of those operations are
> all side effects, which are changes in the
> state of the execution environment."
>
> According to this definition, consider this function,
>
> T ReturnT(){
> T result_;
> //do something
> return result_; // #1
>
> }
>
> At #1, I think
> 1) if T is scalre type such as int or char, the returning sentence
> would not have side effects
> 2) if T is a class type, does returning type T have side effects? and
> Why? I.e. which program state is changed in the T's copy constrcutor.

Could be anything depending upon what's written in the copy
constructor for the specific type T. No? For example, even a simple
print to console or writing something to a log file (both I/O related)
could be considered a side-effect. Copies as in above can be elided
via RVO/NRVO alongwith those side-effects.