Star More Effective Use of Shared Memory on Linux
Linked by Eugenia Loli-Queru on Mon 14th Nov 2005 06:11 UTC
Linux Making effective use of shared memory in high-level languages such as C++ is not straightforward, but it is possible to overcome the inherent difficulties. This article describes, and includes sample code for, two C++ design patterns that use shared memory on Linux in interesting ways and open the door for more efficient interprocess communication.
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Weird Codingstyle
by anda_skoa on Mon 14th Nov 2005 10:39 UTC
anda_skoa
Member since:
2005-07-07

I have seen quite some possibilities to check for a nullpointer, like:

if (!pointer)
if (pointer != NULL)
if (pointer != 0)

but this is the the first time I saw someone check 0 against the the pointer:

if (0 != pointer)

:)

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RE: Weird Codingstyle
by enar on Mon 14th Nov 2005 11:12 in reply to "Weird Codingstyle"
enar Member since:
2005-11-14

It doesn't matter in this case, but if you want to write:

if (pointer == 0)

but make a mistake and type:

if (pointer = 0)

It will compile without any errors.

if (0 = pointer)

will give an error.

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RE[2]: Weird Codingstyle
by anda_skoa on Mon 14th Nov 2005 11:42 in reply to "RE: Weird Codingstyle"
anda_skoa Member since:
2005-07-07

Ah, true, the other style would just give a warning, which can be overlooked.

It's still the first time I saw it.

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RE: Weird Codingstyle
by ma_d on Mon 14th Nov 2005 19:48 in reply to "Weird Codingstyle"
ma_d Member since:
2005-06-29

That's because, TMK, NULL is not guaranteed to be zero in the ansi c standard. But there's a lot of code that does it, and it always seems to be anyway.

NULL is guaranteed to be false though.

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RE[2]: Weird Codingstyle
by japail on Mon 14th Nov 2005 20:17 in reply to "RE: Weird Codingstyle"
japail Member since:
2005-06-30

He was referring to that particular usage of the commutativity of pointer equality. The C++ standard specifically defines 0 as the null pointer constant. So does the C99 standard IIRC.

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