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• Python to C/C++ const char question

  - by tsukemonoki

  I am extending Python with some C++ code. One of the functions I'm using has the following signature: int PyArg_ParseTupleAndKeywords(PyObject *arg, PyObject *kwdict, char *format, char **kwlist, ...); (link: http://docs.python.org/release/1.5.2p2/ext/parseTupleAndKeywords.html) The parameter of interest is kwlist. In the link above, examples on how to use this function are given. In the examples, kwlist looks like: static char *kwlist[] = {"voltage", "state", "action", "type", NULL}; When I compile this using g++, I get the warning: warning: deprecated conversion from string constant to ‘char*’ So, I can change the static char* to a static const char*. Unfortunately, I can't change the Python code. So with this change, I get a different compilation error (can't convert char** to const char**). Based on what I've read here, I can turn on compiler flags to ignore the warning or I can cast each of the constant strings in the definition of kwlist to char *. Currently, I'm doing the latter. What are other solutions? Sorry if this question has been asked before. I'm new.

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• Failed to load url in Dom Document?

  - by Lakhan

  im trying to get latitude and longtitude from google map by giving address. But its giving error.when i directly copy url to browser url bar.its giving correct result.If anybody know the answer .Plz reply. Thanx in advance Here is my code. <?php $key = '[AIzaSyAoPgQlfKsBKQcBGB01cl8KmiPee3SmpU0]'; $opt = array ( 'address' => urlencode('Kolkata,India, ON') , 'output' => 'xml' ); $url = 'http://maps.google.com/maps/geo?q='.$opt['address'].'&output='.$opt['output'].'&oe=utf8&key='.$key; $dom = new DOMDocument(); $dom->load($url); $xpath = new DomXPath($dom); $xpath->registerNamespace('ge', 'http://earth.google.com/kml/2.0'); $statusCode = $xpath->query('//ge:Status/ge:code'); if ($statusCode->item(0)->nodeValue == '200') { $pointStr = $xpath->query('//ge:coordinates'); $point = explode(",", $pointStr->item(0)->nodeValue); $lat = $point[1]; $lon = $point[0]; echo '<pre>'; echo 'Lat: '.$lat.', Lon: '.$lon; echo '</pre>'; } ?> Following error has occured: Warning: DOMDocument::load(http://maps.google.com/maps/geo? q=Kolkata%252CIndia%252C%2BON&output=xml&oe=utf8&key=%5BAIzaSyAoPgQlfKsBKQcBGB01cl8KmiPee3SmpU0%5D) [domdocument.load]: failed to open stream: HTTP request failed! HTTP/1.0 400 Bad Request in C:\xampp\htdocs\draw\draw.php on line 19 Warning: DOMDocument::load() [domdocument.load]: I/O warning : failed to load external entity "http://maps.google.com/maps/geo?q=Kolkata%252CIndia%252C%2BON&output=xml&oe=utf8&key=%5BAIzaSyAoPgQlfKsBKQcBGB01cl8KmiPee3SmpU0%5D" in C:\xampp\htdocs\draw\draw.php on line 19 Notice: Trying to get property of non-object in C:\xampp\htdocs\draw\draw.php on line 26

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• issue with keychain and updates from app store

  - by xonegirlz

  I am having a very frustrating error. I have tested for an app upgrade by first installing the previous version (1.0.1) and then running version (1.0.2). Everything worked fine. I submitted the app and then I am getting issues people are getting crashes when they upgrade. I tried doing the same thing, which is installing the 1.0.1 and then install the binary on the app store, then it crashed. I looked at the console and crash logs and I get this: Jul 7 08:07:45 unknown MyApp[1429] <Warning>: KeychainUtils keychainValueForKey: - Error finding keychain value for key. Status code = -25300 Jul 7 08:07:45 unknown MyApp[1429] <Warning>: AccountSession readUserDataFromDisk - Error finding keychain value for key /var/mobile/Applications/997B32E7-6FFC-4696-9CAA-129BADE2FE64/Documents/instagram_json Jul 7 08:07:45 unknown MyApp[1429] <Warning>: UISegmentedControlStyleBezeled is deprecated. Please use a different style. Jul 7 08:07:45 unknown MyApp[1429] <Error>: *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFDictionary setObject:forKey:]: attempt to insert nil value (key: username)' *** First throw call stack: (0x33ee688f 0x367e7259 0x33ee6789 0x33ee67ab 0x33e5368b 0x14fd99 0x152319 0x1530bb 0x170299 0x3270ec59 0x32711817 0x354e7dfb 0x354e7cd0) Jul 7 08:07:45 unknown UIKitApplication:com.firesnakelabs.pinstagram[0x14e4][1429] <Notice>: terminate called throwing an exception >

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• Is there any seriously good reason why a view can not completely manage itself?

  - by mystify

  Example: I have an warning triangle icon, which is a UIImageView subclass. That warning is blended in with an animation, pulses for 3 seconds and then fades out. it always has a parent view! it's always only used this way: alloc, init, add as subview, kick off animation, when done:remove from superview So I want this: [WarningIcon warningAtPosition:CGPointMake(50.0f, 100.0f) parentView:self]; BANG! That's it. Call and forget. The view adds itself as subview to the parent, then does it's animations. And when done, it cuts itself off from the branch with [self removeFromSupeview];. Now some nerd a year ago told me: "Never cut yourself off from your own branch". In other words: A view should never ever remove itself from superview if it's no more referenced anywhere. I want to get it, really. WHY? Think about this: The hard way, I would do actually the exact same thing. Create an instance and hang me in as delegate, kick off the animation, and when the warning icon is done animating, it calls me back "hey man i'm done, get rid of me!" - so my delegate method is called with an pointer to that instance, and I do the exact same thing: [thatWarningIcon removeFromSuperview]; - BANG. Now I'd really love to know why this sucks. Life would be so easy.

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• "Address of" (&) an array / address of being ignored be gcc?

  - by dbarbosa

  Hi, I am a teaching assistant of a introductory programming course, and some students made this type of error: char name[20]; scanf("%s",&name); which is not surprising as they are learning... What is surprising is that, besides gcc warning, the code works (at least this part). I have been trying to understand and I wrote the following code: void foo(int *str1, int *str2) { if (str1 == str2) printf("Both pointers are the same\n"); else printf("They are not the same\n"); } int main() { int test[50]; foo(&test, test); if (&test == test) printf("Both pointers are the same\n"); else printf("They are not the same\n"); } Compiling and executing: $ gcc test.c -g test.c: In function ‘main’: test.c:12: warning: passing argument 1 of ‘foo’ from incompatible pointer type test.c:13: warning: comparison of distinct pointer types lacks a cast $ ./a.out Both pointers are the same Both pointers are the same Can anyone explain why they are not different? I suspect it is because I cannot get the address of an array (as I cannot have & &x), but in this case the code should not compile.

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• Error while saving csv file generated by PHP

  - by user1667374

  I have created below script which is saving the csv file in the same path of this script but when I am saving it to different directory, it gives me error. Can somebody please help me on this? This is the error: Warning: fopen(/store/secure/mas/) [function.fopen]: failed to open stream: No such file or directory in /getdetails.php on line 15 Warning: fputs(): supplied argument is not a valid stream resource in /getdetails.php on line 36 Warning: fclose(): supplied argument is not a valid stream resource in /getdetails.php on line 39 This is the script: <?php $MYSQL_HOST="localhost"; $MYSQL_USERNAME="***"; $MYSQL_PASSWORD="***"; $MYSQL_DATABASE="shop"; $MYSQL_TABLE="ds_orders"; mysql_connect( "$MYSQL_HOST", "$MYSQL_USERNAME", "$MYSQL_PASSWORD" ) or die( mysql_error( ) ); mysql_select_db( "$MYSQL_DATABASE") or die( mysql_error( $conn ) ); $filename="Order_Details"; $directory = "/store/secure/mas/"; $csv_filename = $filename.".csv"; $fd = fopen ( "$directory" . $cvs_filename, "w"); $today="2009-03-17"; $disp_date="05122008"; $sql = "SELECT * FROM $MYSQL_TABLE where cDate='$today'"; $result=mysql_query($sql); $rows=mysql_num_rows($result); echo $rows; if(mysql_num_rows($result)>0){ $fileContent="Record ID,Discount Percent\n"; while($data=mysql_fetch_array($result)) { $fileContent.= "".$data['oID'].",".$data['discount']."\n"; } $fileContent=str_replace("\n\n","\n",$fileContent); fputs($fd, $fileContent); } fclose($fd); ?>

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• Nested modal view controller gives strange message under iOS6?

  - by user1840362

  I am presenting a modal view controller from another modal view controller, and this worked fine under all iOS versions prior to iOS6. But under iOS6 I am getting the following warning message in the emulator: Warning: Attempt to present <UINavigationController: 0x14e93680> on <UINavigationController: 0x9fc6b70> while a presentation is in progress! The modal view controller is not shown if this warning appears. Basically I am using code like this to show the modal view controller: WebAuthViewController *authController = [[WebAuthViewController alloc] initWithNibName:nil bundle:nil]; authController.challenge = challenge; authController.delegate = self; UINavigationController *aNavController = [[UINavigationController alloc] initWithRootViewController:authController]; [self presentModalViewController:aNavController animated:YES]; [aNavController release]; [authController release]; The view that is already shown is a UIWebView also shown in a modal view, like this: WebViewController *addController = [[WebViewController alloc] initWithNibName:nil bundle:nil]; addController.urlToLoad = [NSURL URLWithString:urlString]; addController.delegate = self; UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:addController]; navigationController.modalTransitionStyle = UIModalTransitionStyleFlipHorizontal; [self presentModalViewController:navigationController animated:YES]; [navigationController release]; [addController release]; The apple docs still suggest that one is supposed to be able to stack navigation controllers like this, so I am at a loss to explain why this happens. Any hints?

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• Deprecated functions not spotted if using "System::Threading::ThreadState" (and others!) C++ VS2005/

  - by Fishboy

  Hi, I'm facing an issue with c++ on vs2005 and also vs2008... here's how you can reproduce the issue.... create a new (c++) project called 'test' (file|new|project) select "Windows Forms Application" and add the 'stdio.h' include and the code fragment below into the test.cpp source file..... -------------------start of snippet-------------------- #include <stdio.h> ... int main(array<System::String ^> ^args) { int i; System::Threading::ThreadState state; char str[20]; sprintf (str, "%s", "test string"); ... -------------------end of snippet-------------------- If you compile the code as above (you'll have to 'buildall' first), you'll get two warnings about 'i' and 'state' being unreferenced (nothing about sprintf being deprecated). If you comment out "System::Threading :Thread state;", you'll get one warning about 'i' being unreferenced and another warning (C4996) for the 'deprecated' sprintf statement.... This issue also occurs for "System::Windows::Forms::MessageBoxIcon", "System::Base64FormattingOptions" (and perhap all 'enum class' types!) Anyone know of the cause and workaround to the issue demonstrated here ( i have other files that demonstate this issue..). (I had started a thread on msdn, but then found this site! see link below) Visual Studio 2005 has stopped warning about deprecated functions

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• Could this C cast to avoid a signed/unsigned comparison make any sense?

  - by sharptooth

  I'm reviewing a C++ project and see effectively the following: std::vector<SomeType> objects; //then later int size = (int)objects.size(); for( int i = 0; i < size; ++i ) { process( objects[i] ); } Here's what I see. std::vector::size() returns size_t that can be of some size not related to the size of int. Even if sizeof(int) == sizeof(size_t) int is signed and can't hold all possible values of size_t. So the code above could only process the lower part of a very long vector and contains a bug. That said I'm curious of why the author might have written this? My only guess is that first he omitted the (int) cast and the compiler emitted something like Visual C++ C4018 warning: warning C4018: '<' : signed/unsigned mismatch so the author though that the best way to avoid the compiler warning would be to simply cast the size_t to int thus making the compiler shut up. Is there any other possible sane reason for that C cast?

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• Header redirect and Session start() generating errors

  - by RPK

  I am using following code. I get errors: Warning: Cannot modify header information - headers already sent by (output started at /home/public_html/mc/cpanel/Source/verifylogin.php:11) Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at /home/public_html/mv/cpanel/Source/verifylogin.php:11) Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at /home/public_html/mv/cpanel/Source/verifylogin.php:11) <?php error_reporting(E_ALL^ E_NOTICE); ob_start(); require("../Lib/dbaccess.php"); $inQuery = "SELECT mhuserid, mhusername FROM cpanelusers WHERE mhusername = '". $_POST['UserName'] ."' AND mhpassword = '". hash('sha512', $_POST['Password']) ."'"; try { $Result = dbaccess::GetRows($inQuery); echo $Result; $NumRows = mysql_num_rows($Result); if ($NumRows > 0) { header("Location: http://www.example.com/cpanel/mainwindow.php"); session_start(); } else { header("Location: http://www.example.com/cpanel/"); echo "Last login attempt failed."; exit; } } catch(exception $e) { } ob_clean(); ?>

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• Looking for something to add some standard rules for my c++ project.

  - by rkb

  Hello all, My team is developing a C++ project on linux. We use vim as editor. I want to enforce some code standard rules in our team in such a way that if the code is not in accordance with it, some sort of warning or error will be thrown when it builds or compiles. Not necessarily it builds but at least I can run some plugin or tools on that code to make sure it meets the standard. So that before committing to svn everyone need to run the code through some sort of plugin or script and make sure it meets the requirement and then only he/she can commit. Not sure if we can add some rules to vim, if there are any let me know about it. For eg. In our code standards all the member variables and private functions should start with _ class A{ private: int _count; float _amount; void _increment_count(){ ++_count; } } So I want to throw some warning or error or some sort of messages for this class if the variables are declared as follows. class A{ private: int count; float amount; void increment_count(){ ++_count; } } Please note that warning and error are not from compiler becoz program is still valid. Its from the tool I want to use so that code goes to re-factoring but still works fine on the executable side. I am looking for some sort of plugin or pre parsers or scripts which will help me in achieving all this. Currently we use svn; just to anser the comment.

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• E: Sub-process /usr/bin/dpkg returned an error code (1) seems to be choking on kde-runtime-data version issue

  - by BMT

  12.04 LTS, on a dell mini 10. Install stable until about a week ago. Updated about 1x a week, sometimes more often. Several days ago, I booted up and the system was no longer working correctly. All these symptoms occurred simultaneously: Cannot run (exit on opening, every time): Update manager, software center, ubuntuOne, libreOffice. Vinagre autostarts on boot, no explanation, not set to startup with Ubuntu. Using apt-get to fix install results in the following: maura@pandora:~$ sudo apt-get -f install Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following package was automatically installed and is no longer required: libtelepathy-farstream2 Use 'apt-get autoremove' to remove them. The following extra packages will be installed: gwibber gwibber-service kde-runtime-data software-center Suggested packages: gwibber-service-flickr gwibber-service-digg gwibber-service-statusnet gwibber-service-foursquare gwibber-service-friendfeed gwibber-service-pingfm gwibber-service-qaiku unity-lens-gwibber The following packages will be upgraded: gwibber gwibber-service kde-runtime-data software-center 4 upgraded, 0 newly installed, 0 to remove and 39 not upgraded. 20 not fully installed or removed. Need to get 0 B/5,682 kB of archives. After this operation, 177 kB of additional disk space will be used. Do you want to continue [Y/n]? debconf: Perl may be unconfigured (Can't locate Scalar/Util.pm in @INC (@INC contains: /etc/perl /usr/local/lib/perl/5.14.2 /usr/local/share/perl/5.14.2 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.14 /usr/share/perl/5.14 /usr/local/lib/site_perl .) at /usr/lib/perl/5.14/Hash/Util.pm line 9. BEGIN failed--compilation aborted at /usr/lib/perl/5.14/Hash/Util.pm line 9. Compilation failed in require at /usr/share/perl/5.14/fields.pm line 122. Compilation failed in require at /usr/share/perl5/Debconf/Log.pm line 10. Compilation failed in require at (eval 1) line 4. BEGIN failed--compilation aborted at (eval 1) line 4. ) -- aborting (Reading database ... 242672 files and directories currently installed.) Preparing to replace gwibber 3.4.1-0ubuntu1 (using .../gwibber_3.4.2-0ubuntu1_i386.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/gwibber_3.4.2-0ubuntu1_i386.deb (--unpack): subprocess new pre-removal script returned error exit status 1 Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace gwibber-service 3.4.1-0ubuntu1 (using .../gwibber-service_3.4.2-0ubuntu1_all.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/gwibber-service_3.4.2-0ubuntu1_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace kde-runtime-data 4:4.8.3-0ubuntu0.1 (using .../kde-runtime-data_4%3a4.8.4-0ubuntu0.1_all.deb) ... Unpacking replacement kde-runtime-data ... dpkg: error processing /var/cache/apt/archives/kde-runtime-data_4%3a4.8.4-0ubuntu0.1_all.deb (--unpack): trying to overwrite '/usr/share/sounds', which is also in package sound-theme-freedesktop 0.7.pristine-2 dpkg-deb (subprocess): subprocess data was killed by signal (Broken pipe) dpkg-deb: error: subprocess <decompress> returned error exit status 2 Preparing to replace python-crypto 2.4.1-1 (using .../python-crypto_2.4.1-1_i386.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/python-crypto_2.4.1-1_i386.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace software-center 5.2.2.2 (using .../software-center_5.2.4_all.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/software-center_5.2.4_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Preparing to replace xdiagnose 2.5 (using .../archives/xdiagnose_2.5_all.deb) ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: warning: subprocess old pre-removal script returned error exit status 1 dpkg - trying script from the new package instead ... Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pyclean", line 25, in <module> import logging ImportError: No module named logging dpkg: error processing /var/cache/apt/archives/xdiagnose_2.5_all.deb (--unpack): subprocess new pre-removal script returned error exit status 1 No apport report written because MaxReports is reached already Could not find platform dependent libraries <exec_prefix> Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>] Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging Error in sys.excepthook: Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/apport_python_hook.py", line 64, in apport_excepthook from apport.fileutils import likely_packaged, get_recent_crashes File "/usr/lib/python2.7/dist-packages/apport/__init__.py", line 1, in <module> from apport.report import Report File "/usr/lib/python2.7/dist-packages/apport/report.py", line 16, in <module> from xml.parsers.expat import ExpatError File "/usr/lib/python2.7/xml/parsers/expat.py", line 4, in <module> from pyexpat import * ImportError: No module named pyexpat Original exception was: Traceback (most recent call last): File "/usr/bin/pycompile", line 27, in <module> import logging ImportError: No module named logging dpkg: error while cleaning up: subprocess installed post-installation script returned error exit status 1 Errors were encountered while processing: /var/cache/apt/archives/gwibber_3.4.2-0ubuntu1_i386.deb /var/cache/apt/archives/gwibber-service_3.4.2-0ubuntu1_all.deb /var/cache/apt/archives/kde-runtime-data_4%3a4.8.4-0ubuntu0.1_all.deb /var/cache/apt/archives/python-crypto_2.4.1-1_i386.deb /var/cache/apt/archives/software-center_5.2.4_all.deb /var/cache/apt/archives/xdiagnose_2.5_all.deb E: Sub-process /usr/bin/dpkg returned an error code (1) maura@pandora:~$ ^C maura@pandora:~$

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• Nagging As A Strategy For Better Linking: -z guidance

  - by user9154181

  The link-editor (ld) in Solaris 11 has a new feature that we call guidance that is intended to help you build better objects. The basic idea behind guidance is that if (and only if) you request it, the link-editor will issue messages suggesting better options and other changes you might make to your ld command to get better results. You can choose to take the advice, or you can disable specific types of guidance while acting on others. In some ways, this works like an experienced friend leaning over your shoulder and giving you advice — you're free to take it or leave it as you see fit, but you get nudged to do a better job than you might have otherwise. We use guidance to build the core Solaris OS, and it has proven to be useful, both in improving our objects, and in making sure that regressions don't creep back in later. In this article, I'm going to describe the evolution in thinking and design that led to the implementation of the -z guidance option, as well as give a brief description of how it works. The guidance feature issues non-fatal warnings. However, experience shows that once developers get used to ignoring warnings, it is inevitable that real problems will be lost in the noise and ignored or missed. This is why we have a zero tolerance policy against build noise in the core Solaris OS. In order to get maximum benefit from -z guidance while maintaining this policy, I added the -z fatal-warnings option at the same time. Much of the material presented here is adapted from the arc case: PSARC 2010/312 Link-editor guidance The History Of Unfortunate Link-Editor Defaults The Solaris link-editor is one of the oldest Unix commands. It stands to reason that this would be true — in order to write an operating system, you need the ability to compile and link code. The original link-editor (ld) had defaults that made sense at the time. As new features were needed, command line option switches were added to let the user use them, while maintaining backward compatibility for those who didn't. Backward compatibility is always a concern in system design, but is particularly important in the case of the tool chain (compilers, linker, and related tools), since it is a basic building block for the entire system. Over the years, applications have grown in size and complexity. Important concepts like dynamic linking that didn't exist in the original Unix system were invented. Object file formats changed. In the case of System V Release 4 Unix derivatives like Solaris, the ELF (Extensible Linking Format) was adopted. Since then, the ELF system has evolved to provide tools needed to manage today's larger and more complex environments. Features such as lazy loading, and direct bindings have been added. In an ideal world, many of these options would be defaults, with rarely used options that allow the user to turn them off. However, the reality is exactly the reverse: For backward compatibility, these features are all options that must be explicitly turned on by the user. This has led to a situation in which most applications do not take advantage of the many improvements that have been made in linking over the last 20 years. If their code seems to link and run without issue, what motivation does a developer have to read a complex manpage, absorb the information provided, choose the features that matter for their application, and apply them? Experience shows that only the most motivated and diligent programmers will make that effort. We know that most programs would be improved if we could just get you to use the various whizzy features that we provide, but the defaults conspire against us. We have long wanted to do something to make it easier for our users to use the linkers more effectively. There have been many conversations over the years regarding this issue, and how to address it. They always break down along the following lines: Change ld Defaults Since the world would be a better place the newer ld features were the defaults, why not change things to make it so? This idea is simple, elegant, and impossible. Doing so would break a large number of existing applications, including those of ISVs, big customers, and a plethora of existing open source packages. In each case, the owner of that code may choose to follow our lead and fix their code, or they may view it as an invitation to reconsider their commitment to our platform. Backward compatibility, and our installed base of working software, is one of our greatest assets, and not something to be lightly put at risk. Breaking backward compatibility at this level of the system is likely to do more harm than good. But, it sure is tempting. New Link-Editor One might create a new linker command, not called 'ld', leaving the old command as it is. The new one could use the same code as ld, but would offer only modern options, with the proper defaults for features such as direct binding. The resulting link-editor would be a pleasure to use. However, the approach is doomed to niche status. There is a vast pile of exiting code in the world built around the existing ld command, that reaches back to the 1970's. ld use is embedded in large and unknown numbers of makefiles, and is used by name by compilers that execute it. A Unix link-editor that is not named ld will not find a majority audience no matter how good it might be. Finally, a new linker command will eventually cease to be new, and will accumulate its own burden of backward compatibility issues. An Option To Make ld Do The Right Things Automatically This line of reasoning is best summarized by a CR filed in 2005, entitled 6239804 make it easier for ld(1) to do what's best The idea is to have a '-z best' option that unchains ld from its backward compatibility commitment, and allows it to turn on the "best" set of features, as determined by the authors of ld. The specific set of features enabled by -z best would be subject to change over time, as requirements change. This idea is more realistic than the other two, but was never implemented because it has some important issues that we could never answer to our satisfaction: The -z best proposal assumes that the user can turn it on, and trust it to select good options without the user needing to be aware of the options being applied. This is a fallacy. Features such as direct bindings require the user to do some analysis to ensure that the resulting program will still operate properly. A user who is willing to do the work to verify that what -z best does will be OK for their application is capable of turning on those features directly, and therefore gains little added benefit from -z best. The intent is that when a user opts into -z best, that they understand that z best is subject to sometimes incompatible evolution. Experience teaches us that this won't work. People will use this feature, the meaning of -z best will change, code that used to build will fail, and then there will be complaints and demands to retract the change. When (not if) this occurs, we will of course defend our actions, and point at the disclaimer. We'll win some of those debates, and lose others. Ultimately, we'll end up with -z best2 (-z better), or other compromises, and our goal of simplifying the world will have failed. The -z best idea rolls up a set of features that may or may not be related to each other into a unit that must be taken wholesale, or not at all. It could be that only a subset of what it does is compatible with a given application, in which case the user is expected to abandon -z best and instead set the options that apply to their application directly. In doing so, they lose one of the benefits of -z best, that if you use it, future versions of ld may choose a different set of options, and automatically improve the object through the act of rebuilding it. I drew two conclusions from the above history: For a link-editor, backward compatibility is vital. If a given command line linked your application 10 years ago, you have every reason to expect that it will link today, assuming that the libraries you're linking against are still available and compatible with their previous interfaces. For an application of any size or complexity, there is no substitute for the work involved in examining the code and determining which linker options apply and which do not. These options are largely orthogonal to each other, and it can be reasonable not to use any or all of them, depending on the situation, even in modern applications. It is a mistake to tie them together. The idea for -z guidance came from consideration of these points. By decoupling the advice from the act of taking the advice, we can retain the good aspects of -z best while avoiding its pitfalls: -z guidance gives advice, but the decision to take that advice remains with the user who must evaluate its merit and make a decision to take it or not. As such, we are free to change the specific guidance given in future releases of ld, without breaking existing applications. The only fallout from this will be some new warnings in the build output, which can be ignored or dealt with at the user's convenience. It does not couple the various features given into a single "take it or leave it" option, meaning that there will never be a need to offer "-zguidance2", or other such variants as things change over time. Guidance has the potential to be our final word on this subject. The user is given the flexibility to disable specific categories of guidance without losing the benefit of others, including those that might be added to future versions of the system. Although -z fatal-warnings stands on its own as a useful feature, it is of particular interest in combination with -z guidance. Used together, the guidance turns from advice to hard requirement: The user must either make the suggested change, or explicitly reject the advice by specifying a guidance exception token, in order to get a build. This is valuable in environments with high coding standards. ld Command Line Options The guidance effort resulted in new link-editor options for guidance and for turning warnings into fatal errors. Before I reproduce that text here, I'd like to highlight the strategic decisions embedded in the guidance feature: In order to get guidance, you have to opt in. We hope you will opt in, and believe you'll get better objects if you do, but our default mode of operation will continue as it always has, with full backward compatibility, and without judgement. Guidance suggestions always offers specific advice, and not vague generalizations. You can disable some guidance without turning off the entire feature. When you get guidance warnings, you can choose to take the advice, or you can specify a keyword to disable guidance for just that category. This allows you to get guidance for things that are useful to you, without being bothered about things that you've already considered and dismissed. As the world changes, we will add new guidance to steer you in the right direction. All such new guidance will come with a keyword that let's you turn it off. In order to facilitate building your code on different versions of Solaris, we quietly ignore any guidance keywords we don't recognize, assuming that they are intended for newer versions of the link-editor. If you want to see what guidance tokens ld does and does not recognize on your system, you can use the ld debugging feature as follows: % ld -Dargs -z guidance=foo,nodefs debug: debug: Solaris Linkers: 5.11-1.2275 debug: debug: arg[1] option=-D: option-argument: args debug: arg[2] option=-z: option-argument: guidance=foo,nodefs debug: warning: unrecognized -z guidance item: foo The -z fatal-warning option is straightforward, and generally useful in environments with strict coding standards. Note that the GNU ld already had this feature, and we accept their option names as synonyms: -z fatal-warnings | nofatal-warnings --fatal-warnings | --no-fatal-warnings The -z fatal-warnings and the --fatal-warnings option cause the link-editor to treat warnings as fatal errors. The -z nofatal-warnings and the --no-fatal-warnings option cause the link-editor to treat warnings as non-fatal. This is the default behavior. The -z guidance option is defined as follows: -z guidance[=item1,item2,...] Provide guidance messages to suggest ld options that can improve the quality of the resulting object, or which are otherwise considered to be beneficial. The specific guidance offered is subject to change over time as the system evolves. Obsolete guidance offered by older versions of ld may be dropped in new versions. Similarly, new guidance may be added to new versions of ld. Guidance therefore always represents current best practices. It is possible to enable guidance, while preventing specific guidance messages, by providing a list of item tokens, representing the class of guidance to be suppressed. In this way, unwanted advice can be suppressed without losing the benefit of other guidance. Unrecognized item tokens are quietly ignored by ld, allowing a given ld command line to be executed on a variety of older or newer versions of Solaris. The guidance offered by the current version of ld, and the item tokens used to disable these messages, are as follows. Specify Required Dependencies Dynamic executables and shared objects should explicitly define all of the dependencies they require. Guidance recommends the use of the -z defs option, should any symbol references remain unsatisfied when building dynamic objects. This guidance can be disabled with -z guidance=nodefs. Do Not Specify Non-Required Dependencies Dynamic executables and shared objects should not define any dependencies that do not satisfy the symbol references made by the dynamic object. Guidance recommends that unused dependencies be removed. This guidance can be disabled with -z guidance=nounused. Lazy Loading Dependencies should be identified for lazy loading. Guidance recommends the use of the -z lazyload option should any dependency be processed before either a -z lazyload or -z nolazyload option is encountered. This guidance can be disabled with -z guidance=nolazyload. Direct Bindings Dependencies should be referenced with direct bindings. Guidance recommends the use of the -B direct, or -z direct options should any dependency be processed before either of these options, or the -z nodirect option is encountered. This guidance can be disabled with -z guidance=nodirect. Pure Text Segment Dynamic objects should not contain relocations to non-writable, allocable sections. Guidance recommends compiling objects with Position Independent Code (PIC) should any relocations against the text segment remain, and neither the -z textwarn or -z textoff options are encountered. This guidance can be disabled with -z guidance=notext. Mapfile Syntax All mapfiles should use the version 2 mapfile syntax. Guidance recommends the use of the version 2 syntax should any mapfiles be encountered that use the version 1 syntax. This guidance can be disabled with -z guidance=nomapfile. Library Search Path Inappropriate dependencies that are encountered by ld are quietly ignored. For example, a 32-bit dependency that is encountered when generating a 64-bit object is ignored. These dependencies can result from incorrect search path settings, such as supplying an incorrect -L option. Although benign, this dependency processing is wasteful, and might hide a build problem that should be solved. Guidance recommends the removal of any inappropriate dependencies. This guidance can be disabled with -z guidance=nolibpath. In addition, -z guidance=noall can be used to entirely disable the guidance feature. See Chapter 7, Link-Editor Quick Reference, in the Linker and Libraries Guide for more information on guidance and advice for building better objects. Example The following example demonstrates how the guidance feature is intended to work. We will build a shared object that has a variety of shortcomings: Does not specify all it's dependencies Specifies dependencies it does not use Does not use direct bindings Uses a version 1 mapfile Contains relocations to the readonly allocable text (not PIC) This scenario is sadly very common — many shared objects have one or more of these issues. % cat hello.c #include <stdio.h> #include <unistd.h> void hello(void) { printf("hello user %d\n", getpid()); } % cat mapfile.v1 # This version 1 mapfile will trigger a guidance message % cc hello.c -o hello.so -G -M mapfile.v1 -lelf As you can see, the operation completes without error, resulting in a usable object. However, turning on guidance reveals a number of things that could be better: % cc hello.c -o hello.so -G -M mapfile.v1 -lelf -zguidance ld: guidance: version 2 mapfile syntax recommended: mapfile.v1 ld: guidance: -z lazyload option recommended before first dependency ld: guidance: -B direct or -z direct option recommended before first dependency Undefined first referenced symbol in file getpid hello.o (symbol belongs to implicit dependency /lib/libc.so.1) printf hello.o (symbol belongs to implicit dependency /lib/libc.so.1) ld: warning: symbol referencing errors ld: guidance: -z defs option recommended for shared objects ld: guidance: removal of unused dependency recommended: libelf.so.1 warning: Text relocation remains referenced against symbol offset in file .rodata1 (section) 0xa hello.o getpid 0x4 hello.o printf 0xf hello.o ld: guidance: position independent (PIC) code recommended for shared objects ld: guidance: see ld(1) -z guidance for more information Given the explicit advice in the above guidance messages, it is relatively easy to modify the example to do the right things: % cat mapfile.v2 # This version 2 mapfile will not trigger a guidance message $mapfile_version 2 % cc hello.c -o hello.so -Kpic -G -Bdirect -M mapfile.v2 -lc -zguidance There are situations in which the guidance does not fit the object being built. For instance, you want to build an object without direct bindings: % cc -Kpic hello.c -o hello.so -G -M mapfile.v2 -lc -zguidance ld: guidance: -B direct or -z direct option recommended before first dependency ld: guidance: see ld(1) -z guidance for more information It is easy to disable that specific guidance warning without losing the overall benefit from allowing the remainder of the guidance feature to operate: % cc -Kpic hello.c -o hello.so -G -M mapfile.v2 -lc -zguidance=nodirect Conclusions The linking guidelines enforced by the ld guidance feature correspond rather directly to our standards for building the core Solaris OS. I'm sure that comes as no surprise. It only makes sense that we would want to build our own product as well as we know how. Solaris is usually the first significant test for any new linker feature. We now enable guidance by default for all builds, and the effect has been very positive. Guidance helps us find suboptimal objects more quickly. Programmers get concrete advice for what to change instead of vague generalities. Even in the cases where we override the guidance, the makefile rules to do so serve as documentation of the fact. Deciding to use guidance is likely to cause some up front work for most code, as it forces you to consider using new features such as direct bindings. Such investigation is worthwhile, but does not come for free. However, the guidance suggestions offer a structured and straightforward way to tackle modernizing your objects, and once that work is done, for keeping them that way. The investment is often worth it, and will replay you in terms of better performance and fewer problems. I hope that you find guidance to be as useful as we have.

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• BIOS interrupts, privilege levels and paging

  - by Jack

  Hi, I was learning about Intel 8086-80486 CPUs and their interactions with HW. But I still don´t understand it quite well. Please, help me fill blank spots. First, I know that CPU communicates with HW using BIOS interrupts. But, what really happens in PC, when I call some INT instruction? I know that according the interrupt table some instructions begin to execute, but how by executing some instructions can BIOS recognize what I want to do? Becouse as far as I know, CPU has no extra communication channel with BIOS, it can only adress memory and receive data. So how can I instruct BIOS to do something, when I can only address RAM? Next thing I don't understand is about privilege levels. I know about ring model, and access rights, but how does the CPU know which privilege level has executed an instruction? I think that these privileges apply only when intruction is trying to address memory, but how does an application get its privilege level? I mean I know its level 3, but how is it set? And last thing, I know that paging is address scheme that is used to support aplication-transparent virtual memory, or swapping, but I could not find any information about how paging is tied with protected mode. Like if paging is like next mode independent of protected mode, or its somehow implemented within protected mode. And if it is implemented in protected mode, isn´t it too slow, to first address application space, then offset, and then paging folder, page and offset once again?

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• BIOS interrupts, priviledge levels and paging

  - by Jack

  Hi, I was learning about Intel 8086-80486 CPUs and their interactions with HW. But I still don´t understand it quite well. Please, help me fill blank spots. First, I know that CPU communicates with HW using BIOS interrupts. But, what really happens in PC, when I call some INT instruction? I know that according the interrupt table some instructions begin to execute, but how by executing some instructions can BIOS recognize what I want to do? Becouse as far as I know, CPU has no extra communication channel with BIOS, it can only adress memory and receive data. So how can I instruct BIOS to do something, when I can only adress RAM? Next thing I dont understand is about priviledge levels. I know about ring model, and acess rights, but how CPU knows which priviledge level has executed instruction? I think that these priviledges apply only when intruction is trying to adress memory, but how applications gets its priviledge level? I mean I know its level 3, but how its set? And last thing, I know that paging is adress scheme that is used to support aplication-transparent virtual memory, or swaping, but I could not find any informations about how is paging tied with protected mode. Like if paging is like next mode independent of protectet mode, or its somehow implemented within protected mode. And if it is implemented in protected mode, isn´t it too slow, to first adress application space, than offset, and than paging folder, page and offset once again? Thank you for every response.

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• PHP-FPM and APC for shared hosting?

  - by Tiffany Walker

  We are looking into finding a way to get APC to only create one cache per account / site. This can be done with Fastcgi (last update 2006…) but with Fastcgid APC will have to create multiple caches for multiple processes run by the same account. To get around this problem, we have been looking into PHP-FPM PHP process manager allows multiple PHP processes to share a single APC cache. But from what I have read (I hope I'm wrong) , even if you create a pool per process, all sites accross all pools will share the same APC cache. This brings us back to the same problem as with shared Memcached: it's not secure ! On php-fpm's site I read that you can chroot php-fpm pools and define a specific UID and GID per pool… if this is the case then shouldn't APC have to use this user and not have access to other pools cache ? An article here (in 2011) suggests that you would need to run one process per pool creating multiple launchers on different ports and different config files with one pool per config file : http://groups.drupal.org/node/198168 Is this still neceessary ? If so what would be the impact of running say 800 processes of php-fpm ? Would it be mainly memory ? If so how can I work out what the memory impact would be ? I guess that it would be better to run 800 times php-fpm then to have accounts creating multiple APC caches for a single site ? If on average an account creates a 50MB cache and creates 3 caches per account that makes 150Mb per account which makes 120GB… However if each account uses on average only 50Mb that would make 40GB We will have at least 128GB of ram on our next server so 40GB is acceptable if running 800 x PHP-FPM does not create an overhead of more than 20GB ! What do you think is PHP-FPM the best way to go to provide secure APC cache on shared hosting with a server that has a decent amount of memory ? Or should I be looking at another system ? Thanks !

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• The boot selection failed because a required device is inaccessible 0xc000000e

  - by bbodenmiller

  A family member of mine recently went on vacation and turned off their computer, something they normally do not do, upon returning home it would not turn on and now returns the error message below. Generally friends and family come to me for help with computers and I have no problem, however this time I am a bit stumped. Any suggestions would be greatly appreciated. As you can see the error message is: Status: 0xc000000e Info: The best selection failed because a required device is inaccessible. Before going to this error message it briefly flashes the Windows loading screen. I have been able to confirm through the Windows RE Command Line and the dir command that the C: drive is accessible and likely is just suffering a bootup issue. I have tried: Launching the repair process discussed in the error message three times however each time it requires a restart and then returns to the same error message. Changing the boot order to be hard drive first Getting into safe mode; F8 just results in the same error message before I can get to the menu to select safe mode I have checked to make sure the BCD (bcdedit, Boot Configuration Data) is still intact as per https://www.symantec.com/business/support/index?page=content&id=TECH160475 I plan to try (but would like additional comments on): sfc /scannow; requires a restart and thus will likely result in the error message again A memory scan Bootrec as per http://support.microsoft.com/kb/927392#method1 Swapping IDE cables/ports Resetting the BIOS I noticed others with similar issues around the web are dual-booting however this machine is not setup in a dual-boot environment. Additionally at one point this error message supposedly showed up before I started working on the computer: The instruction at 0xfbe2584d referenced memory at 0x00000008. The memory could not be read. As previously stated any additional suggestions or words of advice would be greatly apprecaited.

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• How to set shmall, shmmax, shmni, etc ... in general and for postgresql

  - by jpic

  I've used the documentation from PostgreSQL to set it for example this config: >>> cat /proc/meminfo MemTotal: 16345480 kB MemFree: 1770128 kB Buffers: 382184 kB Cached: 10432632 kB SwapCached: 0 kB Active: 9228324 kB Inactive: 4621264 kB Active(anon): 7019996 kB Inactive(anon): 548528 kB Active(file): 2208328 kB Inactive(file): 4072736 kB Unevictable: 0 kB Mlocked: 0 kB SwapTotal: 0 kB SwapFree: 0 kB Dirty: 3432 kB Writeback: 0 kB AnonPages: 3034588 kB Mapped: 4243720 kB Shmem: 4533752 kB Slab: 481728 kB SReclaimable: 440712 kB SUnreclaim: 41016 kB KernelStack: 1776 kB PageTables: 39208 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 8172740 kB Committed_AS: 14935216 kB VmallocTotal: 34359738367 kB VmallocUsed: 399340 kB VmallocChunk: 34359334908 kB HardwareCorrupted: 0 kB AnonHugePages: 456704 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 12288 kB DirectMap2M: 16680960 kB >>> ipcs -l ------ Shared Memory Limits -------- max number of segments = 4096 max seg size (kbytes) = 4316816 max total shared memory (kbytes) = 4316816 min seg size (bytes) = 1 ------ Semaphore Limits -------- max number of arrays = 128 max semaphores per array = 250 max semaphores system wide = 32000 max ops per semop call = 32 semaphore max value = 32767 ------ Messages Limits -------- max queues system wide = 31918 max size of message (bytes) = 8192 default max size of queue (bytes) = 16384 sysctl.conf extract: kernel.shmall = 1079204 kernel.shmmax = 4420419584 postgresql.conf non defaults: max_connections = 60 # (change requires restart) shared_buffers = 4GB # min 128kB work_mem = 4MB # min 64kB wal_sync_method = open_sync # the default is the first option checkpoint_segments = 16 # in logfile segments, min 1, 16MB each checkpoint_completion_target = 0.9 # checkpoint target duration, 0.0 - 1.0 effective_cache_size = 6GB Is this appropriate ? If not (or not necessarily), in which case would it be appropriate ? We did note nice performance improvements with this config, how would you improve it ? How should kernel memory management parameters be set ? Can anybody explain how to really set them from the ground up ?

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• Laptop choice for development: MacBook Pro 17 vs Dell Studio XPS 16 vs HP Envy 15

  - by Shalan

  Hey! First things first - let me state that I am not intending to play games on this - I have narrowed down to these 3 purely based on specs and its individual brand reliability in the market. I intend to primarily use: Visual Studio 2008 Pro a lot (develop and deploy on Windows platforms) SQL Server 2005 Oracle 10g Adobe Photoshop CS4 Microsoft Expression Studio Google Sketchup I currently use a desktop PC (Core2Duo 2.66Ghz with 3GB DDRII memory) running Vista Business 32-bit - and I have to admit that, especially for Visual Studio, its quite sluggish to a point where it affects productivity. Furthermore, I intend to only use the notebook on a table - with a cooled surface, like granite :) - so I would appreciate people's input with regard to heat issues. Im aware that the Dell's primary exhaust gets blocked by the lid when open, but some reviews don't seem to place extraordinary emphasis on heat issues resulting from this. My options for the Dell/Alienware: Core i7 720QM 4GB DDRIII memory ATI mobility 3670 (512) 128GB Solid State Drive 16-inch Full HD RGB-LED LCD display (1080p) 3-year next-business-day support My configuration for the Apple MBP: Core2Duo 2.8Ghz (Im assuming the T9600) 4GB DDRIII memory 128GB Solid State Drive standard 1 year support The one advantage I think of with the MBP is that I can have the addition of OSX (though Im unsure what I would use it for, but purely to play around with a much-boasted-about OS) What are your thoughts on this, especially regarding build-quality, heat, performance and battery-life? Much thanks! ~shalan

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• Why does my computer crash randomly?

  - by Donavon Decker

  The other day I went out to my van to get my Tower and when I opened the trunk it fell out. I brought it into the house and opened it, and everything looked ok. When I started it up, about 1-3 minutes afterwards it would crash. It did this over and over until I reseated the cooler. Everything seemed normal again, until after about 10 minutes of gameplay (any game), it would crash. I reseated my GPU + reinstalled the drivers, however I still get the same error. A while back, I'd check my 'Windows Rating' periodically, and all of them were in the '6.0-6.9' range except for my hard disk usage (always been like that [not relative]). Today I went in and looked, and my Processor and Memory was rated 5.4. I reseated my cpu and my memory, refreshed the windows rating, and then my processor and memory went from 5.4, to 5.1. A few minutes ago I reseated them once again, and now it's back to 5.4. Note: Not sure if this is relevant to the issue, but I updated my bios earlier today I honestly have no idea what the issue is, but I'm getting aggravated at the problem. Here are some images which contain images of my specifications: i1271.photobucket.com/albums/jj623/donxdeck/1_zps09f0607c.jpg i1271.photobucket.com/albums/jj623/donxdeck/4_zps381cd00a.jpg i1271.photobucket.com/albums/jj623/donxdeck/3_zps54bba720.jpg i1271.photobucket.com/albums/jj623/donxdeck/2_zps945d3d72.jpg Thanks for the help

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• problem booting crusty old windows XP

  - by Carson Myers

  I have an acer aspire laptop running Windows XP home. I believe I have some virus on it, I'm not sure--I mostly just run linux in a VM on it so I wasn't too worried. I'm not sure if that virus caused this problem. The laptop wasn't recognizing my USB hard drive for some reason so I decided to restart it. When it started up, it got past the memory test, past the boot screen, (but it paused right here on a blank screen for awhile) and flashed the desktop once (like it does just before the login screen) and then crashed. I got a quick BSOD and then it restarted. Then it tried to boot again, etc etc infinite loop of failure. Well, before trying safe mode, I disabled automatic restart on system crash so I could read the blue screen. There wasn't anything important on it, it said *** STOP: 0x00000000 (0xC0000000 0x,.... ) beginning physical memory dump physical memory dump complete That's not verbatim (obviously) but it didn't help me. so I booted in safe mode, and it stopped on the driver gagp30kx.sys and then restarted (and infinite loop of failure again). I burned a recovery CD and tried that. It loaded it, and I went into repair mode. I ran chkdsk and then disabled the AGP driver. Same thing on booting in safe mode except it stopped at mup.sys instead. I enabled the AGP driver again, and ran chkdsk again from the CD. It said it found problems but didn't say it fixed them. So I ran it a second time, and it said "performing additional checking or recovery" lots of times (I can't tell how many, they went above the screen top). I tried booting again and no luck. Every time I run chkdsk after trying to boot again it says it found and fixed more errors. I think it might be whatever driver is after the AGP driver, but I don't know what it is or how to find out. Can anyone help me fix this?

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• 613 threads limit on debian

  - by Joel

  When running this program thread-limit.c on my dedicated debian server, the output says that my system can't create more than around 600 threads. I need to create more threads, and fix my system misconfiguration. Here are a few informations about my dedicated server: de801:/# uname -a Linux de801.ispfr.net 2.6.18-028stab085.5 #1 SMP Thu Apr 14 15:06:33 MSD 2011 x86_64 GNU/Linux de801:/# java -version java version "1.6.0_26" Java(TM) SE Runtime Environment (build 1.6.0_26-b03) Java HotSpot(TM) 64-Bit Server VM (build 20.1-b02, mixed mode) de801:/# ldd $(which java) linux-vdso.so.1 => (0x00007fffbc3fd000) libpthread.so.0 => /lib/libpthread.so.0 (0x00002af013225000) libjli.so => /usr/lib/jvm/java-6-sun-1.6.0.26/jre/bin/../lib/amd64/jli/libjli.so (0x00002af013441000) libdl.so.2 => /lib/libdl.so.2 (0x00002af01354b000) libc.so.6 => /lib/libc.so.6 (0x00002af013750000) /lib64/ld-linux-x86-64.so.2 (0x00002af013008000) de801:/# cat /proc/sys/kernel/threads-max 1589248 de801:/# ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 794624 max locked memory (kbytes, -l) 32 max memory size (kbytes, -m) unlimited open files (-n) 10240 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 128 cpu time (seconds, -t) unlimited max user processes (-u) unlimited virtual memory (kbytes, -v) unlimited file locks (-x) unlimited Here is the output of the C program de801:/test# ./thread-limit Creating threads ... Address of c = 1061520 KB Address of c = 1081300 KB Address of c = 1080904 KB Address of c = 1081168 KB Address of c = 1080508 KB Address of c = 1080640 KB Address of c = 1081432 KB Address of c = 1081036 KB Address of c = 1080772 KB 100 threads so far ... 200 threads so far ... 300 threads so far ... 400 threads so far ... 500 threads so far ... 600 threads so far ... Failed with return code 12 creating thread 637. Any ideas how to fix this please ?

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• Fatal Execution Engine Error on the Windows2008 r2, IIS7.5

  - by user66524

  Hi Guys We are running some asp.net(3.5) applications on the Windows2008 r2, IIS7.5. Recently we got some event logs so difficult, we have not idea hope some guys can help. 1.EventID: 1334 (9-1-2011 8:41:57) Error message An error occurred during a process host idle check. Exception: System.AccessViolationException Message: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. StackTrace: at System.Collections.Hashtable.GetEnumerator() at System.Web.Hosting.ApplicationManager.IsIdle() at System.Web.Hosting.ProcessHost.IsIdle() 2.EventID: 1023 (9-1-2011 19:44:02) Error message .NET Runtime version 2.0.50727.4952 - Fatal Execution Engine Error (742B851A) (80131506) 3.EventID: 1000 (9-1-2011 19:44:03) Error message Faulting application name: w3wp.exe, version: 7.5.7600.16385, time stamp: 0x4a5bcd2b Faulting module name: mscorwks.dll, version: 2.0.50727.4952, time stamp: 0x4bebd49a Exception code: 0xc0000005 Fault offset: 0x0000c262 Faulting process id: 0x%9 Faulting application start time: 0x%10 Faulting application path: %11 Faulting module path: %12 Report Id: %13 4.EventID: 5011 (9-1-2011 19:44:03) Error message A process serving application pool 'AppPoolName' suffered a fatal communication error with the Windows Process Activation Service. The process id was '2552'. The data field contains the error number. 5.some info: we got the memory.hdmp(234MB) and minidump.mdmp(19.2) from control panel action center but I donot know how to use that :(

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• Why won't 2GB of ram across 3 of 4 slots work on my motherboard (max 2GB)?

  - by Andrew

  My desktop is an old home-built machine circa 200[5-6] running Ubuntu 11.10 (but this is not relevant because I'm reading available ram from BIOS loading screen), with an ASUS P5GPL motherboard, not X or X-SE - it has four slots. I'm mainly a laptop person, but keep this around for running a server from if needed, backing up to, seeding Ubuntu to people from, etc… It has four (DDR) ram slots, two black and two blue, in the order black-blue-black-blue (I will call them D, C, B, and A, respectively) with some space in the middle. The blue ones are the closest to the processor. I used to have two 512MB chips in the two blue slots. I just got a 1GB chip and plugged it into one of the black slots; my system didn't recognize it. I messed around and discovered that it will not recognize chips in many positions, and I couldn't get it to recognize all three of these chips at the same time. In particular, if I put the 512MB chips in A and B it would only use 1, but AC, AD, BD, and CD worked. I didn't try BC, I believe. Only some of these continue to work when I switch the 1GB chip into one of these positions. Can I have some advice as to how to position these chips to get all 2GB used? How about if I get another 1GB chip - where should I put the two? And what about the RAM maximum Crucial says? Can I go above 2GB, if I get another 1GB chip? Right now, I have a 512MB chip in A and the 1GB chip in C. EDIT: I read some other posts and tried dmidecode in Ubuntu to clarify the max memory question, that wasn't a major part anyways. It says my max memory module size is 1024M (OK) and my max memory size is 4096M (doesn't agree with Crucial OR the Asus web site, maybe it will only work while in Linux and BIOS won't OK it?).

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• PostgreSQL lots of large Arrays and Writes

  - by strife911

  Hi, I am running a python program that spawns 8 threads and as each thread launch its own postmaster process via psycopg2. This is to maximize the use of my CPU-cores (8). Each thread call a series of SQL Functions. Most of these functions go through many thousands of rows each associated to a large FLOAT8[] Array (250-300) values by using unnest() and multiplying each FLOAT8 by an another FLOAT8 associated to each row. This Array approach minimized the size of the Indexes and the Tables. The Function ends with an Insert into another Table of a row of the same form (pk INT4, array FLOAT8[]). Some SQL Functions called by python will Update a row of these kind of Tables (with large Arrays). Now I currently have configured PostgreSQL to use most of the memory for cache (effective_cache_size of 57 GB I think) and only a small amount of it for shared memory (1GB I think). First, I was wondering what the difference between Cache and Shared memory was in regards to PostgreSQL (and my application). What I have noticed is that only about 20-40% of my total CPU processing power is used during the most Read intensive parts of the application (Select unnest(array) etc). So secondly, I was wondering what I could do to improve this so that 100% of the CPU is used. Based on my observations, it does not seem to have anything to do with python or its GIL. Thanks

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