From: Segher Boessenkool <segher@kernel.crashing.org>
To: Paul Mackerras <paulus@samba.org>
Cc: Olof Johansson <olof@lixom.net>,
mahuja@us.ibm.com, linasvepstas@gmail.com,
linuxppc-dev@ozlabs.org
Subject: Re: [PATCH] pseries: phyp dump: Variable size reserve space.
Date: Thu, 10 Apr 2008 05:10:59 +0200 [thread overview]
Message-ID: <3ff8bdda029b9de8bb712012cec39ab3@kernel.crashing.org> (raw)
In-Reply-To: <18429.28416.578860.961632@cargo.ozlabs.ibm.com>
>>>>> + tmp = tmp & ~0x000000001FFFFFFF;
>>
>> Note that this only works as you expect because the constant is
>> signed here -- the extra zeroes do not magically make it a 64-bit
>> number. So it goes 32-bit 0x1fffffff -> 32-bit -0x20000000 ->
>> 64-bit -0x20000000.
>
> Huh? It's not big enough to be negative when considered as a 32-bit
> number...
0x1fffffff isn't, right; and that makes it a signed int. Applying
the complement operator to it turns it negative. And then the
implicit cast (because tmp is 64-bit) makes it 64-bit, still the
same negative value. Which is the expected result, but via a way
too tricky (and fragile) path :-)
Segher
next prev parent reply other threads:[~2008-04-10 3:22 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-07 23:45 [PATCH] pseries: phyp dump: Variable size reserve space Manish Ahuja
2008-04-08 2:43 ` Olof Johansson
2008-04-09 17:32 ` Manish Ahuja
2008-04-09 19:39 ` Segher Boessenkool
2008-04-10 1:36 ` Paul Mackerras
2008-04-10 3:10 ` Segher Boessenkool [this message]
2008-04-09 17:37 ` Manish Ahuja
2008-04-09 18:30 ` Olof Johansson
2008-04-09 18:43 ` Manish Ahuja
2008-04-09 18:59 ` Olof Johansson
2008-04-11 23:31 ` Manish Ahuja
2008-04-15 6:24 ` Paul Mackerras
2008-04-15 22:56 ` Manish Ahuja
2008-04-16 19:42 ` Joel Schopp
2008-04-16 20:22 ` Linas Vepstas
2008-04-18 19:08 ` Manish Ahuja
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