Re: [ros-dev] [ros-diffs] [fireball] 34232: Yuri Sidorov<[e-mail]> - Prevent boolean flags from beingoptimized away by compiler (due to PSEH usage) by making themvolatile. See issue #3408 for more details.

[Alex Ionescu]

Then gcc or PSEH should be fixed, not worked-around.

On 1-Jul-08, at 12:03 PM, Yury Sidorov wrote:

>   Hi,
>
>  It's corner case problem and it occurs only in these functions.
>
>  Code:
>
>  BOOLEAN f = FALSE;
>
>  f = TRUE;
>  call_some_func();
>  f = FALSE;
>
>  gcc optimizer removes TRUE/FALSE assignments, since it knows that f
>  was FALSE before this code block and remains FALSE after. gcc knows
>  nothing about exceptions and SEH and performs such optimizations
>  here...
>
>  Yury Sidorov.
>
>  ----- Original Message -----
>  From: "Alex Ionescu" <ionucu(a)videotron.ca>
>  To: <ros-dev(a)reactos.org>
>  Sent: Tuesday, July 01, 2008 9:28 PM
>  Subject: Re: [ros-dev] [ros-diffs] [fireball] 34232: Yuri
>  Sidorov<jura(a)cp-lab.com> - Prevent boolean flags from beingoptimized
>  away by compiler (due to PSEH usage) by making themvolatile. See issue
>  #3408 for more details.
>
>
> >   What?
> >
> >  Why would the compiler optimize these away? This doesn't make any
> >  sense.
> >
> >  If something is happening to these flags, PSEH should be fixed --
> >  not
> >  making every flag in the source base a volatile.
> >
> >  On 1-Jul-08, at 3:48 AM, fireball(a)svn.reactos.org wrote:
> >
> > >   Author: fireball
> > >  Date: Tue Jul  1 05:48:50 2008
> > >  New Revision: 34232
> > >
> > >  URL: http://svn.reactos.org/svn/reactos?rev=34232&view=rev
> > >  Log:
> > >  Yuri Sidorov <jura(a)cp-lab.com>
> > >  - Prevent boolean flags from being optimized away by compiler (due
> > >  to PSEH usage) by making them volatile.
> > >  See issue #3408 for more details.
> > >
> > >  Modified:
> > >    trunk/reactos/ntoskrnl/mm/virtual.c
> > >
> > >  Modified: trunk/reactos/ntoskrnl/mm/virtual.c
> > >  URL:
> > >
> > > http://svn.reactos.org/svn/reactos/trunk/reactos/ntoskrnl/mm/virtual.c?rev=…
> > >  =
> > >  =
> > >  =
> > >  =
> > >  =
> > >  =
> > >  =
> > >  =
> > >  =
> > >  =
> > >  ====================================================================
> > >  --- trunk/reactos/ntoskrnl/mm/virtual.c [iso-8859-1] (original)
> > >  +++ trunk/reactos/ntoskrnl/mm/virtual.c [iso-8859-1] Tue Jul  1
> > >  05:48:50 2008
> > >  @@ -70,7 +70,7 @@
> > >     PFN_NUMBER MdlBuffer[(sizeof(MDL) / sizeof(PFN_NUMBER)) +
> > >  MI_MAPPED_COPY_PAGES + 1];
> > >     PMDL Mdl = (PMDL)MdlBuffer;
> > >     ULONG TotalSize, CurrentSize, RemainingSize;
> > >  -    BOOLEAN FailedInProbe = FALSE, FailedInMapping = FALSE,
> > >  FailedInMoving;
> > >  +    volatile BOOLEAN FailedInProbe = FALSE, FailedInMapping =
> > >  FALSE, FailedInMoving;
> > >     BOOLEAN PagesLocked;
> > >     PVOID CurrentAddress = SourceAddress, CurrentTargetAddress =
> > >  TargetAddress;
> > >     PVOID MdlAddress;
> > >  @@ -225,7 +225,7 @@
> > >  {
> > >     UCHAR StackBuffer[MI_POOL_COPY_BYTES];
> > >     ULONG TotalSize, CurrentSize, RemainingSize;
> > >  -    BOOLEAN FailedInProbe = FALSE, FailedInMoving, HavePoolAddress
> > >  = FALSE;
> > >  +    volatile BOOLEAN FailedInProbe = FALSE, FailedInMoving,
> > >  HavePoolAddress = FALSE;
> > >     PVOID CurrentAddress = SourceAddress, CurrentTargetAddress =
> > >  TargetAddress;
> > >     PVOID PoolAddress;
> > >     KAPC_STATE ApcState;
> > >  
> >  Best regards,
> >  Alex Ionescu
> >
> >  _______________________________________________
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> >  http://www.reactos.org/mailman/listinfo/ros-dev 
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Best regards,
Alex Ionescu