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  • Google Desktop shortcut Ctrl + Ctrl weird behavior

    - by Leonid
    Just noticed a weird behavior of Google Desktop shortcut Ctrl + Ctrl. This shortcut is supposed to bring Google Desktop search bar to the front. If Ctrl + Ctrl is pressed the search bar appears, but once you release one of the Ctrl keys it will disappear. If you hold one Ctrl key, and press the other twice the search bar will toggle it's state. Do you have any idea how this can be fixed and what can be causing this behaviour?

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  • Monitoring C++ applications

    - by Scott A
    We're implementing a new centralized monitoring solution (Zenoss). Incorporating servers, networking, and Java programs is straightforward with SNMP and JMX. The question, however, is what are the best practices for monitoring and managing custom C++ applications in large, heterogenous (Solaris x86, RHEL Linux, Windows) environments? Possibilities I see are: Net SNMP Advantages single, central daemon on each server well-known standard easy integration into monitoring solutions we run Net SNMP daemons on our servers already Disadvantages: complex implementation (MIBs, Net SNMP library) new technology to introduce for the C++ developers rsyslog Advantages single, central daemon on each server well-known standard unknown integration into monitoring solutions (I know they can do alerts based on text, but how well would it work for sending telemetry like memory usage, queue depths, thread capacity, etc) simple implementation Disadvantages: possible integration issues somewhat new technology for C++ developers possible porting issues if we switch monitoring vendors probably involves coming up with an ad-hoc communication protocol (or using RFC5424 structured data; I don't know if Zenoss supports that without custom Zenpack coding) Embedded JMX (embed a JVM and use JNI) Advantages consistent management interface for both Java and C++ well-known standard easy integration into monitoring solutions somewhat simple implementation (we already do this today for other purposes) Disadvantages: complexity (JNI, thunking layer between native C++ and Java, basically writing the management code twice) possible stability problems requires a JVM in each process, using considerably more memory JMX is new technology for C++ developers each process has it's own JMX port (we run a lot of processes on each machine) Local JMX daemon, processes connect to it Advantages single, central daemon on each server consistent management interface for both Java and C++ well-known standard easy integration into monitoring solutions Disadvantages: complexity (basically writing the management code twice) need to find or write such a daemon need a protocol between the JMX daemon and the C++ process JMX is new technology for C++ developers CodeMesh JunC++ion Advantages consistent management interface for both Java and C++ well-known standard easy integration into monitoring solutions single, central daemon on each server when run in shared JVM mode somewhat simple implementation (requires code generation) Disadvantages: complexity (code generation, requires a GUI and several rounds of tweaking to produce the proxied code) possible JNI stability problems requires a JVM in each process, using considerably more memory (in embedded mode) Does not support Solaris x86 (deal breaker) Even if it did support Solaris x86, there are possible compiler compatibility issues (we use an odd combination of STLPort and Forte on Solaris each process has it's own JMX port when run in embedded mode (we run a lot of processes on each machine) possibly precludes a shared JMX server for non-C++ processes (?) Is there some reasonably standardized, simple solution I'm missing? Given no other reasonable solutions, which of these solutions is typically used for custom C++ programs? My gut feel is that Net SNMP is how people do this, but I'd like other's input and experience before I make a decision.

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  • Changing direction after collision

    - by Balint
    In the first tutorial for GameMaker (catch the clown), I want to set the direction of the clown after the collision with the wall. I want to do it by pressing the wall object with the mouse (before the collision, to set the angle parameter). For example by pressing only once the wall object it would change the clown's direction after collision by 45 degrees, twice by 90 degrees, and so on. How can I do that?

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  • First Look: H.264 and VP8 Compared

    <b>StreamingMedia:</b> "VP8 is now free, but if the quality is substandard, who cares? Well, it turns out that the quality isn't substandard, so that's not an issue, but neither is it twice the quality of H.264 at half the bandwidth. See for yourself."

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  • Free web "caching" services for a web service

    - by Jason Banico
    I have a web service on Google App engine whose data is updated on a daily basis. To minimize bandwidth utilization from mobile clients connecting to it, I'd like to instead have an intermediary site where the clients will be getting their data from, and minimizing hits to my service to once or twice a day only. Is there such a service I can use? I'd like to explore this "pull" option first, before considering "push" options such as publishing to a blog site or a free website host that doesn't have bandwidth caps.

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  • Using stored procedure to call multiple packages at the same time from SSIS Catalog (SSISDB.catalog.start_execution) resulted in deadlock

    - by Kevin Shyr
    Refer to my previous post (http://geekswithblogs.net/LifeLongTechie/archive/2012/11/14/time-to-stop-using-ldquoexecute-package-taskrdquondash-a-way-to.aspx) about dynamic package calling and multiple packages execution in these posts: I only saw this twice, other times the stored procedure was able to call the packages successfully.  After the service pack, I haven't seen it...yet. http://support.microsoft.com/kb/2699720

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  • Blogging Round the World

    It seems that once or twice a week, I run across an Android-developer-oriented site that I hadn’t previously noticed. There are already a few aggregators and directories, and...

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  • MacBook Pro (5,3) Keyboard Weirdness

    - by schwuk
    My MacBook Pro (5,3) works almost completely OOTB (with restricted video and WiFi drivers), but I am experiencing some keyboard weirdness. Specifically to get either (` and ~) or (´ and ¨) I have to press the key twice. Only these two keys behave this way - every other key mapping works. Keyboard settings are: Model: Apple Laptop (due to #538474) Layout: United Kingdom Macintosh (International)

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  • Android - Force Close - Null Pointer on Canvas?

    - by user22241
    Please bear with me. I have a very odd problem. Basically, my app so far, has 3 activities (a main splash screen, an 'options/menu' screen and the main app). If I follow the very specific steps oulined below, I get a 'null pointer exception' in the 2nd activity) and the app force closes...... Here are the steps: Start the app (a game based on Surfaceview), tap through to the third activity so the game is running, then hit the home key so the game is paused and put to the background, the activity/app is ended through DDMS in the SDK then restarted on the device (all OK so far), now if I hit the back key on the device twice in quick succession, it happens. All other sequence of events is fine, even to the point of pressing the back key, waiting for the previous activity to show, then hitting back again - all OK. Only when the back key is pressed twice in quick succession following all the above steps does the problem occur. I'm assuming that the canvas isn't ready as it's showing as 'null' when this happens, but I'm not sure why this is happening as surely it's happening when I'm trying to go back to activity 1, but the logcat shows the error in activity 2. if I stop the activity running my 'doDraw' method (which referenced the canvas), then all is OK - so I can safely assume it is the canvas causing the problem. Also, if I skip my first activity (which is a very basic full-screen button which just displays a splashscreen and waits for the user to tap the screen), and make my 2nd activity the launch activity, again, it is OK. this is the part of the code that I think is probably relevant: @Override public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) { vheight = this.getHeight(); vwidth = this.getWidth(); } @Override public void surfaceCreated(SurfaceHolder holder) { vheight = this.getHeight(); vwidth = this.getWidth(); this.viewWidth = vwidth; this.viewHeight = vheight; if (runthread==false){ if (preThread.getState()==Thread.State.TERMINATED){ preThread = new OptionsThread(thisholder, thiscontext, thishandler); } preThread.setRunning(true); preThread.start();} } @Override public void surfaceDestroyed(SurfaceHolder holder) { preThread.setRunning(false); //Stop the loop boolean retry = true; //Stop the thread while (retry) { try { preThread.join(); retry = false; } catch (InterruptedException e) { } } Thank you all for any help you can offer

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  • Program Installer Not Detecting Internet

    - by KeithS
    Hello I am trying to install a program through the Ubuntu Software Center. Every time I click install I get a Message stating "failed to download package files, check your Internet connection". I have tried different software installs and get the same message. I do have an Internet connection (hence being able to write this), I have restarted the computer and have reset the Internet (twice) but still get the same message. Any Ideas??

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  • A new number one

    - by nospam(at)example.com (Joerg Moellenkamp)
    The Top500 supercomputer list has a new number one: The K Computer, built by Fujitsu, currently combines 68544 SPARC64 VIIIfx CPUs, each with eight cores, for a total of 548,352 cores?almost twice as many as any other system in the TOP500. The K Computer is also more powerful than the next five systems on the list combined.Interestingly this system runs under Linux. And it uses tofu as its interconnect

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  • SATA drives or chipset throwing DRDY ERR and ICRC ABRT

    - by Matt
    I have an SD-VIA-1A2S PCI card with 2 sata ports (and one ATA-133 that isn't used). Two new Western Digital Caviar Green drives (WD10EARS 1TB) throw repeated errors in kern.log (removed date/time/host info for brevity): [ 7.376475] ata2.00: exception Emask 0x12 SAct 0x0 SErr 0x1000500 action 0x6 [ 7.376480] ata2.00: BMDMA stat 0x5 [ 7.376483] ata2: SError: { UnrecovData Proto TrStaTrns } [ 7.376489] ata2.00: cmd c8/00:40:20:00:00/00:00:00:00:00/e0 tag 0 dma 32768 in [ 7.376490] res 51/84:2f:20:00:00/00:00:00:00:00/e0 Emask 0x12 (ATA bus error) [ 7.376493] ata2.00: status: { DRDY ERR } [ 7.376495] ata2.00: error: { ICRC ABRT } [ 7.376504] ata2: hard resetting link I'm using Ubuntu 9.04 - 2.6.28-18-generic, though I have tried live cds of Ubuntu 9.10, Fedora 12 and OpenSUSE 11.2 - all running various 2.6.31 kernels - and all received the same error. Based on testing these drives and this card in two other machines and combos of connecting the drives directly to the motherboard or the add-in card, I'm relatively convinced that it's the VIA chipset that is the problem. Another computer that also has an onboard VIA SATA chipset (like the add-in card) produces the same errors when the drives are directly on that motherboard. I have been able to verify that the drives are perfectly good, and I tried everything I can think of in terms of swapping cables, psu isn't overloaded, etc. The error happens on boot once or twice, after using fdisk on the drive once or twice, and constantly when attempting to sync a new mdadm raid 1 array created on the two drives. Any thoughts on where to go from here - driver/kernel wise? I'm completely open to buying a new PCI add-in card if someone can recommend one with 2 internal sata ports that works well in Debian/Ubuntu. Thanks!

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  • Mac Mini's internet very slow, every other device fine (PC, iPhone, Xbox 360)

    - by alex
    I recently haven't used my Mac Mini for about 5 days (however it was left on). I seem to be able to connect and get great download / upload speeds through my PC, Xbox 360, iPhone and parents' laptop. However, my Mac Mini is very slow. OS X's Mail.app is downloading mail at 0.4kbps and then dropping to 0. Skype file transfers are doing the same. Browsing the net is a terrible experience. It is taking 30 seconds or more to download basic pages. All of my devices connect wirelessly to a Netgear router / modem. I have tried giving the Mac Mini a manual IP, and renew DHCP lease, as well as flush DNS in Terminal. I have also rebooted the router / modem twice, and the Mac Mini twice. Do you know what could be causing this? Thanks Update This is very weird. It is also very slow accessing localhost (setup through MAMP) and also slow to access the Netgear router config pages.

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  • Creating a tar file with checksums included

    - by wazoox
    Here's my problem : I need to archive to tar files a lot ( up to 60 TB) of big files (usually 30 to 40 GB each). I would like to make checksums ( md5, sha1, whatever) of these files before archiving; however not reading every file twice (once for checksumming, twice for tar'ing) is more or less a necessity to achieve a very high archiving performance (LTO-4 wants 120 MB/s sustained, and the backup window is limited). So I'd need some way to read a file, feeding a checksumming tool on one side, and building a tar to tape on the other side, something along : tar cf - files | tee tarfile.tar | md5sum - Except that I don't want the checksum of the whole archive (this sample shell code does just this) but a checksum for each individual file in the archive. I've studied GNU tar, Pax, Star options. I've looked at the source from Archive::Tar. I see no obvious way to achieve this. It looks like I'll have to hand-build something in C or similar to achieve what I need. Perl/Python/etc simply won't cut it performance-wise, and the various tar programs miss the necessary "plugin architecture". Does anyone know of any existing solution to this before I start code-churning ?

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  • Supermicro X8SIL-F with Enermax Modu82+ 625W PSU booting issue

    - by Richard Whitman
    I am assembling a custom PC. The configuration is below: Motherboard: Supermicro X8SIL-F Processor: Intel Xeon 3430 Power Supply: Enermax Modu82+ 625W. Memory: Kingston KVR1333D3LQ8R9S/8GEC 8GBx1 installed in DimmA1 This power switch: Frozen CPU switch When I turn on the PSU, the motherboard tries to start itself before I even push the power switch. The following happens: The CPU fan rotates like once or twice, and then stops. After 1-2 seconds, the CPU fan tries to rotate again and stops after about one or two rotations. Finally, after another 1-2 seconds, it again starts and this time it rotates for about 3-4 seconds before stopping. If I pull out the Power switch, and turn on the PSU, again the MB turns on itself and the following happens: The CPU fan rotates like once or twice, and then stops. After 1-2 seconds, the CPU fan tries to rotate again and stops after about one or two rotations. Finally, after another 1-2 seconds, it again starts and the system boots properly I am sure there is nothing wrong with any of the components, because I have two sets of identical components (2 MBs, 2 CPUs, 2 PSUs, 2 switches and so on). And both of the systems show the same symptoms. Why is the MB booting up by itself? Why does it fail to boot when the Power Switch is installed? Is something wrong with the type of Power Switch I am using? PS: the power switch is installed correctly, I have double checked the MB manual to make sure its connecting the right pins.

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  • How do I count the times each number appears in columns of numbers?

    - by Andy C.
    I am sure this must be easy, but I am inexperienced. About the best way to think of my problem is to think of it as trying to sort and then count lottery numbers. To stay simple, let's do a Pick 3 game. Let's look at 10 drawings. I would split each drawn number into a separate column: DATE BALL#1 BALL#2 BALL#3 3/1 1 3 5 3/2 3 7 8 3/3 2 2 1 3/4 5 7 6 3/5 2 3 1 3/6 0 5 9 3/7 3 7 0 3/8 6 8 4 3/9 2 4 3 3/10 7 1 2 I would like to be able to build formulas into cells that would tell me how many times each number appeared overall, and how many times each number appeared in the position it occurred. Like this (using the above example): Number Overall Count Ball#1 Count Ball#2 Count Ball#3 Count 0 2 1 0 1 1 4 1 1 2 (That is, The number zero appears twice overall, and came up once as the first number drawn; zero times as the middle ball; and once as the third ball. Likewise, the number 1 was drawn four times in our 10-day period. It was the first ball once, the second ball once and the third ball twice.) And so on. All help appreciated. I have access to Excel and Microsoft Works, or of course if there is a Google Docs way to handle this All thanks for any help.

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  • Sending mails via Mutt and Gmail: Duplicates

    - by Chris
    I'm trying to setup mutt wiht gmail for the first time. It seems to work pretty well, however when I send a mail from Mutt i appears twice in Gmail's sent folder. (I assume it's also sent twice - I'm trying to validate that) My configuration (Stripped of coloring): # A basic .muttrc for use with Gmail # Change the following six lines to match your Gmail account details set imap_user = "XX" set smtp_url = "[email protected]@smtp.gmail.com:587/" set from = "XX" set realname = "XX" # Change the following line to a different editor you prefer. set editor = "vim" # Basic config, you can leave this as is set folder = "imaps://imap.gmail.com:993" set spoolfile = "+INBOX" set imap_check_subscribed set hostname = gmail.com set mail_check = 120 set timeout = 300 set imap_keepalive = 300 set postponed = "+[Gmail]/Drafts" set record = "+[Gmail]/Sent Mail" set header_cache=~/.mutt/cache/headers set message_cachedir=~/.mutt/cache/bodies set certificate_file=~/.mutt/certificates set move = no set include set sort = 'threads' set sort_aux = 'reverse-last-date-received' set auto_tag = yes hdr_order Date From To Cc auto_view text/html bind editor <Tab> complete-query bind editor ^T complete bind editor <space> noop # Gmail-style keyboard shortcuts macro index,pager y "<enter-command>unset trash\n <delete-message>" "Gmail archive message" macro index,pager d "<enter-command>set trash=\"imaps://imap.googlemail.com/[Gmail]/Bin\"\n <delete-message>" "Gmail delete message" macro index,pager gl "<change-folder>" macro index,pager gi "<change-folder>=INBOX<enter>" "Go to inbox" macro index,pager ga "<change-folder>=[Gmail]/All Mail<enter>" "Go to all mail" macro index,pager gs "<change-folder>=[Gmail]/Starred<enter>" "Go to starred messages" macro index,pager gd "<change-folder>=[Gmail]/Drafts<enter>" "Go to drafts" macro index,pager gt "<change-folder>=[Gmail]/Sent Mail<enter>" "Go to sent mail" #Don't prompt on exit set quit=yes ## ================= #Color definitions ## ================= set pgp_autosign

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  • How can I make a copy of a printer in Win7?

    - by hawbsl
    Has anyone been able to copy an existing printer in Win7? I know that we were able to do this in XP (not as a direct copy/paste, but by installing the printer twice) but in Win7 it doesn't seem to be possible. Googling the answer is hopeless because searching for "copy printer" or "duplicate printer" you get a bunch of posts about "printer copiers" or people complaining about duplicate printers getting created in the background (precisely what I'd like to be able to do) It'd be good to know how to do it in general, but if it depends on the printer type, then in our case we are trying to make a copy of an HP Laserjet. Tried installing from the CD - but the CD is too old for Win7 Tried installing via Add Printer and that seems to install the printer but it's marked with an error. Tried installing via the .exe installer from the HP site and that does result in a successful printer being installed, but it won't let you install the same printer twice (stalls on the "insert USB cable now" step - simply won't enable the greyed out "Next" button). The reason this is required is so that we can print to one to the feeder and to the tray separately.

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  • How can I get multiple video cards to work on linux?

    - by user17943
    I installed fedora 12. I have 2 ATI cards that I used to use on windows to run 4 monitors. A recurring problem has been to get them detected in linux. Only my secondary card is picked up linux. When I manage the displays it detects the 2 monitors connected that card. What are the specific steps I should take to get the second card detected? Supposedly there is a tool system-config-xfree. I don't have it, yum can't find it. Also I heard it has something to do with editing some xorg.conf file or something to that effect. I have absolutely no idea how to find the "bus id" of my card, or lookup the horizontal refresh rates, etc.. I would probably have no problem following the documentation & editing the file if I knew a good way to find these values. Someone also suggested installing linux twice and saving the xorg.conf it generates each time (with different card each time) and then merging the two by hand. That is like killing a fly with a hammer though, when I do this again and again in the future It'd be nice to not have to take twice as long. Thanks

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  • Ubuntu's garbage collection cron job for PHP sessions takes 25 minutes to run, why?

    - by Lamah
    Ubuntu has a cron job set up which looks for and deletes old PHP sessions: # Look for and purge old sessions every 30 minutes 09,39 * * * * root [ -x /usr/lib/php5/maxlifetime ] \ && [ -d /var/lib/php5 ] && find /var/lib/php5/ -depth -mindepth 1 \ -maxdepth 1 -type f -cmin +$(/usr/lib/php5/maxlifetime) ! -execdir \ fuser -s {} 2> /dev/null \; -delete My problem is that this process is taking a very long time to run, with lots of disk IO. Here's my CPU usage graph: The cleanup running is represented by the teal spikes. At the beginning of the period, PHP's cleanup jobs were scheduled at the default 09 and 39 minutes times. At 15:00 I removed the 39 minute time from cron, so a cleanup job twice the size runs half as often (you can see the peaks get twice as wide and half as frequent). Here are the corresponding graphs for IO time: And disk operations: At the peak where there were about 14,000 sessions active, the cleanup can be seen to run for a full 25 minutes, apparently using 100% of one core of the CPU and what seems to be 100% of the disk IO for the entire period. Why is it so resource intensive? An ls of the session directory /var/lib/php5 takes just a fraction of a second. So why does it take a full 25 minutes to trim old sessions? Is there anything I can do to speed this up? The filesystem for this device is currently ext4, running on Ubuntu Precise 12.04 64-bit. EDIT: I suspect that the load is due to the unusual process "fuser" (since I expect a simple rm to be a damn sight faster than the performance I'm seeing). I'm going to remove the use of fuser and see what happens.

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  • AT91SAM7X512's SPI peripheral gets disabled on write to SPI_TDR

    - by Dor
    My AT91SAM7X512's SPI peripheral gets disabled on the X time (X varies) that I write to SPI_TDR. As a result, the processor hangs on the while loop that checks the TDRE flag in SPI_SR. This while loop is located in the function SPI_Write() that belongs to the software package/library provided by ATMEL. The problem occurs arbitrarily - sometimes everything works OK and sometimes it fails on repeated attempts (attemp = downloading the same binary to the MCU and running the program). Configurations are (defined in the order of writing): SPI_MR: MSTR = 1 PS = 0 PCSDEC = 0 PCS = 0111 DLYBCS = 0 SPI_CSR[3]: CPOL = 0 NCPHA = 1 CSAAT = 0 BITS = 0000 SCBR = 20 DLYBS = 0 DLYBCT = 0 SPI_CR: SPIEN = 1 After setting the configurations, the code verifies that the SPI is enabled, by checking the SPIENS flag. I perform a transmission of bytes as follows: const short int dataSize = 5; // Filling array with random data unsigned char data[dataSize] = {0xA5, 0x34, 0x12, 0x00, 0xFF}; short int i = 0; volatile unsigned short dummyRead; SetCS3(); // NPCS3 == PIOA15 while(i-- < dataSize) { mySPI_Write(data[i]); while((AT91C_BASE_SPI0->SPI_SR & AT91C_SPI_TXEMPTY) == 0); dummyRead = SPI_Read(); // SPI_Read() from Atmel's library } ClearCS3(); /**********************************/ void mySPI_Write(unsigned char data) { while ((AT91C_BASE_SPI0->SPI_SR & AT91C_SPI_TXEMPTY) == 0); AT91C_BASE_SPI0->SPI_TDR = data; while ((AT91C_BASE_SPI0->SPI_SR & AT91C_SPI_TDRE) == 0); // <-- This is where // the processor hangs, because that the SPI peripheral is disabled // (SPIENS equals 0), which makes TDRE equal to 0 forever. } Questions: What's causing the SPI peripheral to become disabled on the write to SPI_TDR? Should I un-comment the line in SPI_Write() that reads the SPI_RDR register? Means, the 4th line in the following code: (The 4th line is originally marked as a comment) void SPI_Write(AT91S_SPI *spi, unsigned int npcs, unsigned short data) { // Discard contents of RDR register //volatile unsigned int discard = spi->SPI_RDR; /* Send data */ while ((spi->SPI_SR & AT91C_SPI_TXEMPTY) == 0); spi->SPI_TDR = data | SPI_PCS(npcs); while ((spi->SPI_SR & AT91C_SPI_TDRE) == 0); } Is there something wrong with the code above that transmits 5 bytes of data? Please note: The NPCS line num. 3 is a GPIO line (means, in PIO mode), and is not controlled by the SPI controller. I'm controlling this line by myself in the code, by de/asserting the ChipSelect#3 (NPCS3) pin when needed. The reason that I'm doing so is because that problems occurred while trying to let the SPI controller to control this pin. I didn't reset the SPI peripheral twice, because that the errata tells to reset it twice only if I perform a reset - which I don't do. Quoting the errata: If a software reset (SWRST in the SPI Control Register) is performed, the SPI may not work properly (the clock is enabled before the chip select.) Problem Fix/Workaround The SPI Control Register field, SWRST (Software Reset) needs to be written twice to be cor- rectly set. I noticed that sometimes, if I put a delay before the write to the SPI_TDR register (in SPI_Write()), then the code works perfectly and the communications succeeds. Useful links: AT91SAM7X Series Preliminary.pdf ATMEL software package/library spi.c from Atmel's library spi.h from Atmel's library An example of initializing the SPI and performing a transfer of 5 bytes is highly appreciated and helpful.

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  • Why is x=x++ undefined?

    - by ugoren
    It's undefined because the it modifies x twice between sequence points. The standard says it's undefined, therefore it's undefined. That much I know. But why? My understanding is that forbidding this allows compilers to optimize better. This could have made sense when C was invented, but now seems like a weak argument. If we were to reinvent C today, would we do it this way, or can it be done better? Or maybe there's a deeper problem, that makes it hard to define consistent rules for such expressions, so it's best to forbid them? So suppose we were to reinvent C today. I'd like to suggest simple rules for expressions such as x=x++, which seem to me to work better than the existing rules. I'd like to get your opinion on the suggested rules compared to the existing ones, or other suggestions. Suggested Rules: Between sequence points, order of evaluation is unspecified. Side effects take place immediately. There's no undefined behavior involved. Expressions evaluate to this value or that, but surely won't format your hard disk (strangely, I've never seen an implementation where x=x++ formats the hard disk). Example Expressions x=x++ - Well defined, doesn't change x. First, x is incremented (immediately when x++ is evaluated), then it's old value is stored in x. x++ + ++x - Increments x twice, evaluates to 2*x+2. Though either side may be evaluated first, the result is either x + (x+2) (left side first) or (x+1) + (x+1) (right side first). x = x + (x=3) - Unspecified, x set to either x+3 or 6. If the right side is evaluated first, it's x+3. It's also possible that x=3 is evaluated first, so it's 3+3. In either case, the x=3 assignment happens immediately when x=3 is evaluated, so the value stored is overwritten by the other assignment. x+=(x=3) - Well defined, sets x to 6. You could argue that this is just shorthand for the expression above. But I'd say that += must be executed after x=3, and not in two parts (read x, evaluate x=3, add and store new value). What's the Advantage? Some comments raised this good point. It's not that I'm after the pleasure of using x=x++ in my code. It's a strange and misleading expression. What I want is to be able to understand complicated expressions. Normally, a complicated expression is no more than the sum of its parts. If you understand the parts and the operators combining them, you can understand the whole. C's current behavior seems to deviate from this principle. One assignment plus another assignment suddenly doesn't make two assignments. Today, when I look at x=x++, I can't say what it does. With my suggested rules, I can, by simply examining its components and their relations.

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  • IOs7 app crashing when in background

    - by Leonardo
    My app sometimes crashes when in background and shows the following crash log: Nov 7 12:33:31 iPad backboardd[29] <Warning>: MyApp[3096] has active assertions beyond permitted time: {( <BKProcessAssertion: 0x14680c60> identifier: Called by MyApp, from -[AppDelegate applicationDidEnterBackground:] process: MyApp[3096] permittedBackgroundDuration: 180.000000 reason: finishTask owner pid:3096 preventSuspend preventIdleSleep preventSuspendOnSleep )} Looking through other questions I found out that the crash message indicates that I didn't end a task properly, so when its time expired the OS ended it and crashed my app. So I added some NSLogs: - (void)applicationDidEnterBackground:(UIApplication *)application { [self saveContext]; [Settings setCallLock:YES]; [self saveStuff]; if ([self isBackgroundTaskNeeded]) { UIApplication* app = [UIApplication sharedApplication]; bgTask = [app beginBackgroundTaskWithExpirationHandler:^{ [self pauseDownloads]; NSLog(@"Debug - Ending background task %d",bgTask); [app endBackgroundTask:bgTask]; NSLog(@"Debug - Background task %d ended",bgTask); bgTask = UIBackgroundTaskInvalid; }]; NSLog(@"Debug - Starting background task %d",bgTask); [self initBackground]; } } and found out that the task was called twice when it crashed: Nov 7 12:30:02 iPad MyApp[3096] <Warning>: Debug - Starting background task 7 Nov 7 12:30:30 iPad MyApp[3096] <Warning>: Debug - Starting background task 8 Nov 7 12:33:26 iPad MyApp[3096] <Warning>: Debug - Ending background task 8 Nov 7 12:33:26 iPad MyApp[3096] <Warning>: Debug - Background task 8 ended Nov 7 12:33:26 iPad MyApp[3096] <Warning>: Debug - Ending background task 0 Nov 7 12:33:26 iPad MyApp[3096] <Warning>: Debug - Background task 0 ended I wasn't able to tell when the double call happens and why. So question is why is the task being called twice and is there a way to avoid it? Edit: - (void) pauseDownloads { for (AFDownloadRequestOperation *operation in self.operationQueue.operations) { if(![operation isPaused]) { [operation pause]; } } }

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