array variable subscript generate wrong code (2008) ?

[brof777]

here is the code:
DWORD SomeFunction(DW ORD Dw_0, DWORD Dw_1, DWORD Dw_2)
{
return Dw_0 + Dw_1 + Dw_2;
}
void main()
{
DWORD Dw = 0;
DWORD pDw[3] = {1,2,3};
DWORD Dw_Sum = SomeFunction(pD w[Dw++], pDw[Dw++], pDw[Dw++]);
}
I expected VC++ 2008 generate code as SomeFunction(3, 2,1) or
SomeFunction(1, 2,3), however, the real code is like
SomeFunction(1, 1,1)
I debug the and watch assembly code, find the code was generated with
push pDw[0] 3 times, then increase Dw by 3 times.
Can anyone tell me why?

[Ismo Salonen]

br*****@gmail.c om wrote:

here is the code:
DWORD SomeFunction(DW ORD Dw_0, DWORD Dw_1, DWORD Dw_2)
{
return Dw_0 + Dw_1 + Dw_2;
}
void main()
{
DWORD Dw = 0;
DWORD pDw[3] = {1,2,3};
DWORD Dw_Sum = SomeFunction(pD w[Dw++], pDw[Dw++], pDw[Dw++]);
}
I expected VC++ 2008 generate code as SomeFunction(3, 2,1) or
SomeFunction(1, 2,3), however, the real code is like
SomeFunction(1, 1,1)
I debug the and watch assembly code, find the code was generated with
push pDw[0] 3 times, then increase Dw by 3 times.
Can anyone tell me why?

This code has undefined behaviour, Dw++ is executed three times but it
is not defined when exactly that happens. This is quite classic example
like x = i++ + i++;

br
ismo

[David Wilkinson]

br*****@gmail.c om wrote:

here is the code:
DWORD SomeFunction(DW ORD Dw_0, DWORD Dw_1, DWORD Dw_2)
{
return Dw_0 + Dw_1 + Dw_2;
}
void main()
{
DWORD Dw = 0;
DWORD pDw[3] = {1,2,3};
DWORD Dw_Sum = SomeFunction(pD w[Dw++], pDw[Dw++], pDw[Dw++]);
}
I expected VC++ 2008 generate code as SomeFunction(3, 2,1) or
SomeFunction(1, 2,3), however, the real code is like
SomeFunction(1, 1,1)
I debug the and watch assembly code, find the code was generated with
push pDw[0] 3 times, then increase Dw by 3 times.
Can anyone tell me why?

brof:

Please don't multi-post. This question has nothing to do with .NET, so it should
not be here anyway.

--
David Wilkinson
Visual C++ MVP