June 2010 - Darwin-dev - lists.apple.com

Re: Basic C query.
by Arnab Ganguly 24 Jun '10

24 Jun '10

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Re: Daemon Communication
by Jens Alfke 24 Jun '10

24 Jun '10

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha1; c=relaxed; d=mooseyard.com; h=subject :mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; s= mooseyard.com; bh=AVlfVMzIhVxKxxffhmSwQZMrPqA=; b=KF8Zr2iAkj0pwA 2BjL+8VuJotV7btsoJlsghsVFiuQwUMy0cwGn1NJcsmj7EvNZWiat1YwYMmy82ay F7dLVUx7qdPmrE4hq6xj0vUkWlZFaIM+/QYiwoLOrZkY/J2wpGuQbCXEXCdRMYHk 4KlQiwCciuSvvhYbcuw0fdx9Kr4Kk= Domainkey-signature: a=rsa-sha1; c=nofws; d=mooseyard.com; h=subject :mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; q=dns; s= mooseyard.com; b=nKuXmYsfwVr5OKQX93EEf4YCQj8YHcWgrEe70I4ASX0LWUg hFPOzWq2YcaTTLh42De3bWcrqPyeFaT8pjgTHgXeEd5zTgjL/BqmbOkjlU7tp3SY 27RBcaqtcGgbkT/lRGpUYRlv3N7S++dji+wkZ1sMfB3rYXqjV7gNzLzbVtWM= On Jun 24, 2010, at 5:37 AM, Paolo Ambrosio wrote: > I am in the process of starting the development of a daemon that > should interact with local CLI and GUI clients Are you sure you really need a daemon and not an agent? Daemons are harder to write since they don’t run as a “real” user or within a regular login session. Moreover, if you run a daemon as root, you have to be very careful about security. > "Apple > recommends that you use UNIX domain sockets for client/daemon > communication". Does Spotlight use this method? A lot of Apple stuff uses Mach messages, with MIG as the RPC mechanism. I think this is not recommended for 3rd party developers because there isn’t good documentation for it (for some reason Apple has never released real docs for Mach-level stuff, so you often have to dig up old NeXT docs or even stuff from the CMU Mach project.) > i read that Carbon and Cocoa are not > available for use in daemon code, and it makes sense. Does it mean > that I won't be able to vend an object using Distributed Objects > (without an agent wrapping Cocoa messages to the Unix Socket)? “Cocoa” is a marketing term, not a real framework :) Or rather, it’s used as an aggregate term for Foundation + AppKit. AppKit definitely shouldn’t be used in a daemon or agent. Foundation is safe for agents, and I would guess that subsets of Foundation are safe for daemons — the core Obj-C stuff should be OK, but I have no idea what things like NSUserDefaults will do if they’re not running as a regular GUI account with a Library/ subdirectory. —Jens _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Re: Basic C query.
by Arnab Ganguly 24 Jun '10

24 Jun '10

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Daemon Communication
by Paolo Ambrosio 24 Jun '10

24 Jun '10

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:mime-version:received:from:date :message-id:subject:to:content-type; bh=tiMk5vBYKOXFcttGyU3yXy4/6Idg7gL6iW9lFwPkfq0=; b=LwwQJio2pOQHnKSNVwdiA099ClMGqavkjIz3ihWtlwwJeBXj33lvNnb6AJyG8qZLoe eZg56fp4l7n91dqZv0ZsCDlPUM2CVKNKwfXh116rI5dFO0i/mN0PQHi55tr0lwcTSybb 3KGnMjw3k2nF69Q2PG74e5TE8nNV08BxBlxeM= Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:from:date:message-id:subject:to:content-type; b=uwQuQRd8GFILC6ojSDroo/Z3EbE4LVgKNKJfJfs5WLrO9JkSptCxHQ2J4t9BpcufWX Q7Jn+ucqyH4gCddGuy/yRtO5cJsxYDlgol5ELxiimJ0LGq371+mwc3RiEkJHtQRqKkhi q6btZjrh5Wyew9oFLDRp/9ZNmxg+7NSRbe4OI= Hello, I am in the process of starting the development of a daemon that should interact with local CLI and GUI clients (for service control and data query). It should be similar to what Spotlight does, with the daemon running at system startup, a command line client as "mdfind", a menubar item, etc. In the "Daemons and Agents" Technical Note TN2083 [1], "Apple recommends that you use UNIX domain sockets for client/daemon communication". Does Spotlight use this method? Being new to the Darwin/Apple world, I have another question also. In the Daemon-Safe Frameworks Table i read that Carbon and Cocoa are not available for use in daemon code, and it makes sense. Does it mean that I won't be able to vend an object using Distributed Objects (without an agent wrapping Cocoa messages to the Unix Socket)? Can you point me in the right direction? I hope I was not too off topic for this list. If I was, please tell me where those questions are appropriate. Thanks, Paolo 1: http://developer.apple.com/mac/library/technotes/tn2005/tn2083.html _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Re: Basic C query.
by Alastair Houghton 23 Jun '10

23 Jun '10

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha1; c=relaxed; d=coriolis-systems.com; h= subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; s=aug07; bh=A+0ilO/UOCLYjUJbh3xqMXdG05k=; b=wq6howrMOnWWSebkL6JSpOoCFT/j c12Ua3q6P5x5DqjyDwQ5+eAL4mSAEeE64yVZayDS1xZDdAWco3b/ulX6uWTuQno7 Ur6JvmnL7qzMTQdmYmkNf6EBYgX0ULHY9Yhicv0g5i6txMZIAgqCKThKXTVUUKMX kUGn5MO/+vfazz4= On 23 Jun 2010, at 15:53, Arnab Ganguly wrote: > Sorry for posting a basic C question. Then don't. There are plenty of good places to ask C questions (like comp.lang.c, Stack Overflow, the Yahoo c-prog user group...) Please use one of those in future. You might think I'm being unfair, but if we don't collectively discourage off-topic posts, pretty soon we'll have people asking how best to grow their onions, and then where will we be? :-) Kind regards, Alastair. -- http://alastairs-place.net _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Re: Basic C query.
by Rohitash Panda 23 Jun '10

23 Jun '10

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com User-agent: Thunderbird 2.0.0.24 (X11/20100411) Dear All, Sorry for posting a basic C question.Below is the code base. struct Test { int a; int b; }; //member offset. int result = (((Test *) 8)->a) - 8; I get bus error for this. I am not clear about the logic as what exactly ((Test *) 8)->a signifies here and why -8 is done. I have copy pasted a smaller portion of the main code.Only one line written as Member offset. The above code works fine in 32bit but in 64bit I am getting issue if I can understand the above logic will be more clear as what needs to be done. Use offsetof() http://en.wikipedia.org/wiki/Offsetof _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This is a classic case of trying to implement offsetof() as Peter suggested , but having platform dependent behavior . This follows from the below idiomatic construct of offsetof() implementation: #define offsetof(type, field) ((size_t)((char *)&((type *)0)->field - (char *)(type *)0)) Portable 'C' code should instead use the platform offsetof() implementations available . Peter O'Gorman wrote: On 06/23/2010 09:53 AM, Arnab Ganguly wrote: Peter _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/rohitash.panda%40oracle.c… This email sent to rohitash.panda(a)oracle.com This email sent to site_archiver(a)lists.apple.com

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Re: Basic C query.
by Jens Alfke 23 Jun '10

23 Jun '10

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com Dkim-signature: v=1; a=rsa-sha1; c=relaxed; d=mooseyard.com; h=subject :mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; s= mooseyard.com; bh=RAEL8QETp0wesxTPk7HT5pHDEts=; b=MsnJv+OV09IR3N 2vKxZbfP0TYjGE4QGeQb9JNeMGTQ0cR7wp1j2S4u0bFXPHrkptQmBP26/9N3c1yu D7SVwPddx63K4vZPVeUTDYxMcbzbNy8HYYFdN5NZgwN5yZq8l/RvONeXIykB7K25 NXDE3CAxcmxI0vuqIugtTmWfcKETM= Domainkey-signature: a=rsa-sha1; c=nofws; d=mooseyard.com; h=subject :mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; q=dns; s= mooseyard.com; b=Yy2g5NvT6is09Ra9t6kk4qWZ5lvG1pK7KnKgRqzUitp4k4V 9EpFIc0tnliUmUWOkxzu46FeolyR+sR0f/D8JS7HGX9PUHz9qXBlV87YPXxcmfrw b3sg45LwThLxmmnF5jEMxqwF8QV/Vkf+WPjyOBSlsr80sqeqvLWuDbiYuW3I= On Jun 23, 2010, at 7:53 AM, Arnab Ganguly wrote: > int result = (((Test *) 8)->a) - 8; You could fix this by adding an &: int result = &(((Test *) 8)->a) - 8; but this construct is so ugly and hard to understand that you really should use offsetof( ) instead. —Jens _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… This email sent to site_archiver(a)lists.apple.com

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Re: Basic C query.
by Peter O'Gorman 23 Jun '10

23 Jun '10

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.9) Gecko/20100430 Fedora/3.0.4-3.fc13 Thunderbird/3.0.4 Dear All, Sorry for posting a basic C question.Below is the code base. struct Test { int a; int b; }; //member offset. int result = (((Test *) 8)->a) - 8; I get bus error for this. I am not clear about the logic as what exactly ((Test *) 8)->a signifies here and why -8 is done. I have copy pasted a smaller portion of the main code.Only one line written as Member offset. The above code works fine in 32bit but in 64bit I am getting issue if I can understand the above logic will be more clear as what needs to be done. Use offsetof() http://en.wikipedia.org/wiki/Offsetof Peter _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… On 06/23/2010 09:53 AM, Arnab Ganguly wrote: This email sent to site_archiver(a)lists.apple.com

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Re: Basic C query.
by Jamison Hope 23 Jun '10

23 Jun '10

site_archiver(a)lists.apple.com Delivered-To: darwin-dev(a)lists.apple.com On Jun 23, 2010, at 10:53 AM, Arnab Ganguly wrote: Dear All, Sorry for posting a basic C question.Below is the code base. struct Test { int a; int b; }; //member offset. int result = (((Test *) 8)->a) - 8; This would work: #include <stdint.h> /* for intptr_t */ #include <stdio.h> /* for printf */ struct Test { int a; int b; }; typedef struct Test Test; int main(void) { Test t; t.a = 10; intptr_t an_integer = (intptr_t)&t; -Jamie -- Jamison Hope The PTR Group www.theptrgroup.com _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev(a)lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.app… I get bus error for this. I am not clear about the logic as what exactly ((Test *) 8)->a signifies here and why -8 is done. You're taking the number 8 and casting it as a pointer to a Test. You're then taking this alleged Test* and accessing the member field called "a", which is an int, and subtracting 8 from it, storing the difference in "result". The -8 is a red herring; the reason you're getting a bus error is that the memory at address 8 does not, in fact, contain a Test structure, but rather some kernel stuff you aren't allowed to touch from user code. [Incidentally, if this is actually vanilla C and not C++, there should be a "typedef struct Test Test;" somewhere as well in order to associate the Test in "((Test *) 8)" with struct Test.] int result = (((Test *) an_integer)->a) - 8; /* notice I am using a known address and not an integer literal */ printf("result: %d\n", result); return 0; } This email sent to site_archiver(a)lists.apple.com

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Basic C query.
by Arnab Ganguly 23 Jun '10

23 Jun '10

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