Re: What is the right way to print a UINTN?

["Kinney, Michael D" <michael.d.kinney@intel.com>]

Hi Brian,

This is a good idea.  I will have to study it some more 
to figure out what the EBC versions of these macros would
map to.

Mike

> -----Original Message-----
> From: Brian J. Johnson [mailto:bjohnson@sgi.com]
> Sent: Tuesday, September 27, 2016 10:14 AM
> To: Andrew Fish <afish@apple.com>; Eugene Cohen <eugene@hp.com>
> Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Alexei Fedorov
> <Alexei.Fedorov@arm.com>; edk2-devel@lists.01.org <edk2-devel@ml01.01.org>; Laszlo
> Ersek <lersek@redhat.com>
> Subject: Re: [edk2] What is the right way to print a UINTN?
> 
> On 09/27/2016 11:47 AM, Andrew Fish wrote:
> >
> >> On Sep 27, 2016, at 9:03 AM, Cohen, Eugene <eugene@hp.com> wrote:
> >>
> >>> Printing UINTN with %x *or* with %d are equally bugs.
> >>>
> >>> For X64 / AARCH64 / IA64 builds, they are actual bugs (that happen to
> >>> work most of the time).
> >>
> >> Feel free to file a Bugzilla on the extensive usage of this in
> >> edk2 [ducking and running]. :)
> >>
> >>>> I'm envisioning having to create a slide in the future for UEFI
> >>>> training about the proper use of UINTNs and describing "If you think
> >>>> it may exceed 2^32-1 then upcast to UINT64, otherwise don't worry
> >>>> about it" and it makes me squirm.
> >>>
> >>> It makes me squirm too. I think the slide should recommend the
> >>> casting
> >>> that I proposed. ;) "There is no conversion specifier dedicated to
> >>> UINTN; the portable way to print it is to cast it to UINT64, then print
> >>> it with %Lx."
> >>
> >> This is reasonable although I expect to get asked why a lot of the
> >> other code doesn't adhere to this recommendation.
> >>
> >
> > I think this is a historical artifact. The older version of %x in
> > the EDK (and early edk2) implied UINTN. We hit an issue with C
> > integer math resulting in an int and that seemed to bork some
> > toolchains. That is when things changed from UINTN to int. I guess
> > the cleanup was practical vs. pedantic.
> 
> Thanks for the historical context, Andrew.  It's interesting to hear,
> if very unfortunate.
> 
> I've written code in the past which uses a #defined value for the
> UINTN format character as a way to work around this issue without
> casting everything to 64 bits.  Something like:
> 
> // Format string for a naturally-sized unsigned integer
> #if defined (MDE_CPU_IA32)
> #define UINTN_FMT  "0x%08x"
> #elif defined (MDE_CPU_X64)
> #define UINTN_FMT  "0x%016lx"
> #elif ...
>    ...
> #endif
> 
> UINTN Val;
> Val = Foo ();
> DEBUG((DEBUG_INFO, "Value is " UINTN_FMT "\n", Val));
> 
> 
> I guess it's a matter of opinion if that's preferable to adding casts;
> in my particular situation, I had to print values with that particular
> format string in a lot of places, so it was convenient to #define it
> once.
> 
> >
> > Thanks,
> >
> > Andrew Fish
> >
> >> Thanks,
> >>
> >> Eugene
> >> _______________________________________________
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> >
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> >
> 
> 
> --
> 
> 						Brian J. Johnson
> 
> --------------------------------------------------------------------
> 
>    My statements are my own, are not authorized by SGI, and do not
>    necessarily represent SGI's positions.