Re: 0xdeadbeef vs 0xdeadbeefL

[Gabriel Paubert]

On Wed, Jul 07, 2004 at 04:10:28AM -0700, tom st denis wrote:
> --- viro@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx wrote:
> > On Tue, Jul 06, 2004 at 05:06:12PM -0700, tom st denis wrote:
> > > --- David Eger <eger@xxxxxxxxxxxxx> wrote:
> > > > Is there a reason to add the 'L' to such a 32-bit constant like
> > this?
> > > > There doesn't seem a great rhyme to it in the headers...
> > > 
> > > IIRC it should have the L [probably UL instead] since numerical
> > > constants are of type ``int'' by default.  
> > > 
> > > Normally this isn't a problem since int == long on most platforms
> > that
> > > run Linux.  However, by the standard 0xdeadbeef is not a valid
> > unsigned
> > > long constant.
> > 
> > ... and that would be your F for C101.  Suggested remedial reading
> > before
> > you take the test again: any textbook on C, section describing
> > integer
> > constants; alternatively, you can look it up in any revision of C
> > standard.
> > Pay attention to difference in the set of acceptable types for
> > decimal
> > and heaxdecimal constants.
> 
> You're f'ing kidding me right?  Dude, I write portable ISO C source
> code for a living.  My code has been built on dozens and dozens of
> platforms **WITHOUT** changes.  I know what I'm talking about.
> 
> 0x01, 1 are 01 all **int** constants.
> 
> On some platforms 0xdeadbeef may be a valid int, in most cases the
> compiler won't diagnostic it.  splint thought it was worth mentioning
> which is why I replied.
> 
> In fact GCC has odd behaviour.  It will diagnostic
> 
> char x = 0xFF;
> 
> and
> 
> int x = 0xFFFFFFFFULL;
> 
> But not 
> 
> int x = 0xFFFFFFFF;
> 
> [with --std=c99 -pedantic -O2 -Wall -W]
> 
> So I'd say it thinks that all of the constants are "int".  In this case
> 0xFF is greater than 127 [max for char] and 0xFFFFFFFFFFULL is larger

You are aware that this statement is plainly and simply wrong, 
aren't you?

On many platforms a "plain" char is unsigned. You can't write portable
code without knowing this.

> 
> Before you step down to belittle others I'd suggest you actually make
> sure you're right.  

Ditto.

	Gabriel
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