Coding problem

[Jon]

Can anyone see why this would work:

MessageBox(NULL, vParams[0].szValue(), "", MB_OK);

but this doesn't:

const char *szValue = vParams[0].szValue();
MessageBox(NULL, szValue, "", MB_OK);

Given that .szValue() returns "const char *"

:iamstupid:

[Valik]

Very strange. I say blame Microsoft just because it's fun.

Have you re-written any of the Variant or VectorVariant code since 3.0.76? That's the last copy of the source I have downloaded so it's the one I looked at. Using it for reference, I see no reason why that code won't work (For what my opinions worth, I probably have less programming experience than all of you). Could it maybe have something to do with the subscripting operator? I threw together a simple class where a function returned a const char* to a dynamically allocated array and I experienced no abnormalities. The only thing I didn't test was subscripting. :: shrugs ::

:iamstupid: :iamstupid:

Edited December 17, 2003 by Valik

[Jon]

Hmm, I thought it was odd too so am just trying to work out if it's like you say a subscript bug.

This works, so it looks like the variant creation, assignment and copy constructors are working ok:

const char *pszValue;
    Variant vTest;
    vTest = "Hello";

    MessageBox(NULL, vTest.szValue(), "", MB_OK);
    pszValue = vTest.szValue();
    MessageBox(NULL, pszValue, "", MB_OK);

    Variant vTestCopy(vTest);
    MessageBox(NULL, vTestCopy.szValue(), "", MB_OK);
    pszValue = vTestCopy.szValue();
    MessageBox(NULL, pszValue, "", MB_OK);

    vTestCopy = vTest;
    MessageBox(NULL, vTestCopy.szValue(), "", MB_OK);
    pszValue = vTestCopy.szValue();
    MessageBox(NULL, pszValue, "", MB_OK);

[Jon]

Bah, I see it. Look at the declaration of the subscript in vectorvariant:

Variant      operator[](unsigned int nIndex);   // Overloaded []

[Valik]

I love stupid bugs like that. They're what makes programming worth killing yourself over.

[Jon]

All my stacks, vectors, tokens everything had the same declaration, and while not technically a bug I'm now returning references everywhere instead of these temporary "copies".

Result:

- Everything is faster (less copying)

- Uncompressed EXE reduced by 30KB! (78KB compressed)

- All vectors can be modifed as well as just read: e.g. vParams[0] = ...

This is one of those times I realise how complicated C++ can be...

[jpm]

I am wondering why only m_nNull dummy is initialize and not the m_sNull, m_vNull.

is the value never used? only the reference

[Jon]

It's never used. And the Variant (unlike an integer) sets itself up with a valid value when it is created.

[spt]

if it dont work, tinker with it a bit, and maybe then it will work lol

either that or give bill gates a call