AcString?

[Anonymous]

const ACHAR* WhatIsReturned()
{
      AcString a = L"Test";
      AcString b = L" this";
      AcString c = a + b;
      return c;
}

 What happens to c when this method returns. Does the underlying string encapsulated by c get lost when c goes out of scope or is a copy of the const ACHAR* returned?

Mike

[Alexander.Rivilis · Accepted solution]

After return from this function destructor of "c" do returned pointer invalid. You do not use such code. IMHO.

[owenwengerd]

Memory for all three local strings is freed before the function returns. The code is not correct.

[Anonymous]

Yeah, I figured as much, but I was thinking that one of the overloads would return a new ACHAR*. I realized after I posted that this was a "cloudy mind moment" realizing that even if a new ACHAR* was returned, there was no way to free it. Will a AcString be returned by value? Or would that be freed as well.

AcString TestThis()
{
    AcString a = L"Test";
    AcString b = L" this!";
    AcString c = a + b;

    return c;
}

In this code, would 'c' be returned by value or would it still go out of scope?

Mike

[Alexander.Rivilis]

---

@Anonymous wrote:

Yeah, I figured as much, but I was thinking that one of the overloads would return a new ACHAR*. I realized after I posted that this was a "cloudy mind moment" realizing that even if a new ACHAR* was returned, there was no way to free it. Will a AcString be returned by value? Or would that be freed as well.

AcString TestThis()
{
    AcString a = L"Test";
    AcString b = L" this!";
    AcString c = a + b;

    return c;
}

In this code, would 'c' be returned by value or would it still go out of scope?

Mike

---

In this code compile create copy of 'c' and return it. After that destructor of 'c' will be called. So you have a valid value of 'c' after calling TestThis():

AcString d = TestThis();

[owenwengerd · Accepted solution]

It's common to return AcString by value, but functions should almost never accept string arguments as AcString by value. Almost always, string arguments should be typed as const ACHAR* or at least const AcString&. Example (untested):

AcString myConcatStr1(const ACHAR* in1, const ACHAR* in2)
{
  AcString in1Str(in1);
  return in1Str + in2;
}

AcString myConcatStr2(const AcString& in1Str, const AcString& in2Str)
{
  return in1Str + in2Str;
}

void test()
{
  AcString s1 = _ACRX_T("Test");
  AcString s2 = _ACRX_T(" String");
  AcString s3 = myConcatStr1(s1, s2);
  AcString s4 = myConcatStr2(s1, s2);
}