Re: Heap usage and variable argument C functions

[David Jones <drj@...>]

On Dec 21, 2004, at 11:13, David Given wrote:

> On Tuesday 21 December 2004 04:39, Brett Bibby wrote:
>
> > The
> > main issues are implicit type casting between double and float and 
> > long and
> > ints.  For example, on platforms like the PS2 you have to be really 
> > careful
> > that you don't accidentally enable emulated doubles.  Also, we have
> > denormal trouble on the PC when using Lua and DirectX together.  Each 
> > time
> > a new Lua is released we spend at least a full day fixing all the 
> > warnings.
>
> But aren't you *allowed* to implicitly cast between double and float 
> and long
> and int? Unfortunately I don't have my copy of the C standard here, 
> but I'm
> reasonably sure that's all legal. Not meaning to quibble, but it 
> sounds as if
> your warnings are platform-specific, due to one of the C standard's
> assumptions not being entirely true on your platform... can you quote 
> a few?

Of course you are allowed to implicitly case between double and float.  
That's why it's a warning, not an error.  You _allowed_ to write 
"if(x=0)", but it's still probably a mistake.  Almost all warnings 
produces by all C compilers are for legal code (or code that could, in 
principle, be legal in some circumstances).

I remember one compiler (possibly Codewarrior?) that got very touchy 
with double to float conversion (and to be fair it is a big issue on 
some platforms, it's not always cheap to generate the correct code), 
even to the point of complaining about "float f = 1.0;"

David Jones