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  • Setting WCF service for multiple client calls

    - by user348255
    Hi all, I have made a WCF service which is defined like this: [ServiceBehavior(InstanceContextMode = InstanceContextMode.Single, ConcurrencyMode = ConcurrencyMode.Multiple)] binding is done using netTcpBinding. We support 50+ clients that call the server from time to time. Each client opens a channel using channelfactory once it is loaded and uses that channel for all calls (creates the channel and proxy only once). we have built a small load tester that imitates the client by calling the server by 50 different threads at once (using 50 different channels). when we run this tester, after the 10th client tries to connect, all other client fail connecting. We have set throttling to 100. My questions are: 1. is it correct for each client to create a channel and use it through the client life time? or, do i need to use a using statement for each call to the server (create and distroy a new channel for each call). 2. does the service have a limit of channel connections to it? other then throttling? thanks alot, Guy.

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  • The application has stopped unexpectedly: How to Debug?

    - by Android Eve
    Please note, unlike many other questions having the subject title "application has stopped unexpectedly", I am not asking for troubleshooting a particular problem. Rather, I am asking for an outline of the best strategy for an Android/Eclipse/Java rookie to tackle this formidable task of digesting huge amounts of information in order to develop (and debug!) a simple Android application. In my case, I took the sample skeleton app from the SDK, modified it slightly and what did I get the moment I try to run it? The application (process.com.example.android.skeletonapp) has stopped unexpectedly. Please try again. OK, so I know that I have to look LogCat. It's full of timestamped lines staring at me... What do I do now? What do I need to look for? Is there a way to single-step the program, to find the statement that makes the app crash? (I thought Java programs never crash, but apparently I was mistaken) How do I place a breakpoint? Can you recommend an Android debug tutorial online, other than this one?

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  • jQuery validation plugin - no error messages instead custom backgrounds

    - by Skoota
    I am using the jQuery validation plugin. The form which is being validated has custom background images for the text input fields, so instead of showing an error message for invalid fields I would like to change the background image. Making things a bit trickier is that the background image for the fields is on a different div absolutely positioned behind the text field (which has a transparent background and no border). I will spare going into the reasons for this design decision here (it's related to margins within the text field) but I thought it should be mentioned since it is critical to this question. Therefore, I have two questions: How can I stop the display of the error messages all-together? How can I instead tell the validation plugin if, for example, the name field (e.g. <input id=name ... />) is invalid then it should change the background for the relevant div (e.g. <div id=name-bg... ></div>)? Thanks for any assistance!

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  • Using Lucene to index private data, should I have a separate index for each user or a single index

    - by Nathan Bayles
    I am developing an Azure based website and I want to provide search capabilities using Lucene. (structured json objects would be indexed and stored in Lucene and other content such as Word documents, etc. would be indexed in lucene but stored in blob storage) I want the search to be secure, such that one user would never see a document belonging to another user. I want to allow ad-hoc searches as typed by the user. Lastly, I want to query programmatically to return predefined sets of data, such as "all notes for user X". I think I understand how to add properties to each document to achieve these 3 objectives. (I am listing them here so if anyone is kind enough to answer, they will have better idea of what I am trying to do) My questions revolve around performance and security. Can I improve document security by having a separate index for each user, or is including the user's ID as a parameter in each search sufficient? Can I improve indexing speed and total throughput of the system by having a separate index for each user? My thinking is that having separate indexes would allow me to scale the system by having multiple index writers (perhaps even on different server instances) working at the same time, each on their own index. Any insight would be greatly appreciated. Regards, Nate

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  • Why does setting the margin on a div not affect the position of child content?

    - by DanM
    I'd like to understand a little more clearly how css margins work with divs and child content. If I try this... <div style="clear: both; margin-top: 2em;"> <input type="submit" value="Save" /> </div> ...the Save button is right up against the User Role (margin fail): If I change it to this... <div style="clear: both;"> <input style="margin-top: 2em;" type="submit" value="Save" /> </div> ...there is a gap between the Save button and the User Role (margin win): Questions: Can someone explain what I'm observing? Why doesn't putting a margin on the div cause the input to move down? Why must I put the margin on the input itself? There must be some fundamental law of css I am not grasping.

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  • Sharing a global/static variable between a process and DLL

    - by minjang
    I'd like to share a static/global variable only between a process and a dll that is invoked by the process. The exe and dll are in the same memory address space. I don't want the variable to be shared among other processes. Elaboration of the problem: Say that there is a static/global variable x in a.cpp. Both the exe foo.exe and the dll bar.dll have a.cpp, so the variable x is in both images. Now, foo.exe dynamically loads (or statically) bar.dll. Then, the problem is whether the variable x is shared by the exe and dll, or not. In Windows, these two guys never share the x: the exe and dll will have a separate copy of x. However, in Linux, the exe and dll do share the variable x. Unfortunately, I want the behavior of Linux. I first considered using pragma data_seg on Windows. However, even if I correctly setup the shared data segment, foo.exe and bar.dll never shares the x. Recall that bar.dll is loaded into the address space of foo.exe. However, if I run another instance of foo.exe, then x is shared. But, I don't want x to be shared by different processes. So, using data_seg was failed. I may it use a memory-mapped file by making an unique name between exe and dll, which I'm trying now. Two questions: Why the behavior of Linux and Windows is different? Can anyone explain more about this? What would be most easiest way to solve this problem on Windows?

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  • Writing a synchronized thread-safety wrapper for NavigableMap

    - by polygenelubricants
    java.util.Collections currently provide the following utility methods for creating synchronized wrapper for various collection interfaces: synchronizedCollection(Collection<T> c) synchronizedList(List<T> list) synchronizedMap(Map<K,V> m) synchronizedSet(Set<T> s) synchronizedSortedMap(SortedMap<K,V> m) synchronizedSortedSet(SortedSet<T> s) Analogously, it also has 6 unmodifiedXXX overloads. The glaring omission here are the utility methods for NavigableMap<K,V>. It's true that it extends SortedMap, but so does SortedSet extends Set, and Set extends Collection, and Collections have dedicated utility methods for SortedSet and Set. Presumably NavigableMap is a useful abstraction, or else it wouldn't have been there in the first place, and yet there are no utility methods for it. So the questions are: Is there a specific reason why Collections doesn't provide utility methods for NavigableMap? How would you write your own synchronized wrapper for NavigableMap? Glancing at the source code for OpenJDK version of Collections.java seems to suggest that this is just a "mechanical" process Is it true that in general you can add synchronized thread-safetiness feature like this? If it's such a mechanical process, can it be automated? (Eclipse plug-in, etc) Is this code repetition necessary, or could it have been avoided by a different OOP design pattern?

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  • How to use urlencoded urls with the GA tracking code

    - by Fake51
    I've got a site where a booking page has an iframe embedded with the actual booking form. I need to track traffic from the parent site to the child iframe. This should all work just fine with the normal GA code, using javascript like: <script type="text/javascript"> try { var pageTracker = _gat._getTracker("<UA CODE HERE>"); pageTracker._setDomainName("none"); pageTracker._setAllowLinker(true); pageTracker._setAllowHash(false); pageTracker._trackPageview(); } catch(err) {}</script> And then ofcourse using the _getLinkerUrl() function to get a url with the proper parameters. So far so good - this basically works (at least I know the principle works as I've got it working on other pages). However, and this is the problem: the server that serves up the page in the iframe was configured by a complete and utter moron (or, alternatively, created by a complete and utter moron). It chokes on '=' characters, so in order to request the iframe page I need to urlencode the '=' signs - but the GA code seems unable to parse the url when this is done. So the questions: 1. has anyone come across this? 2. does anyone know of any solutions to this problem?

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  • How to use JSF h:messages better?

    - by gurupriyan.e
    My Objective is to use h:messages to convey user - error and confirmation messages.The CSS styles to show these two different messages are different, In fact I would like to use an image beside the confirmation message. for Eg: <tr> <td><img/></td><td><h:msg></td> </td>. So I tried to add messages to the Faces Context based on 2 different client ids <tr> <td height="5"> <h:messages style="color:darkred" id="error_message" /> </td> </tr> <tr> <td width="89%" class="InfoMsg" align="center"> <h:messages id="confirm_message" /> </td> </tr> and in the java layer FacesMessage facesMessage = new FacesMessage(Constants.saveMessageConfirm); FacesContext.getCurrentInstance().addMessage(Constants.STATIC_CONFIRM_MSG_CLIENT_ID, facesMessage); But, even if i add messages to client Id confirm_message - and only to confirm_message - and not to error_message - The message is shown twice in 2 different styles (refer the HTML above) 2 Questions : 1) What is the problem here? 2) If I want to show the image inside a td in the second tr and conditionaly show that second tr when confirm messages are present - what is the best way? Thanks,

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  • Error monitoring/handling on webservers

    - by Industrial
    Hi everybody, We have a web server that we're about to launch a number of applications onto. They will all share database and memcached servers, but each application has it's own mySQL database and all memcached keys per application, is prefixed. Possible scenario: If a memcached server in our cluster goes boom, we want someone (operative system admin) to be automatically contacted by email/iphone push notification or in any other appropriate way. If we we're about to install 150 identical applications for our customers on our servers, and a memcached server dies - all 150 applications will individually find this out and contact our system admin, which most certainly is going to think about getting a new job where he or she isn't about to be woken up by getting 150 messages sent 4:15 in the morning. Possible solution: One idea is to set up an external server for error handling that gets a $_POST or cURL request sent, and handles storage of the error message depending on the seriousness of the actual error message. It would of course check upon receiving the error call, that if the same memcached server have already been reported as offline, there would be no need to spam the system admin with additional reminders... The questions: What's a good approach on how to handle errors? How does the big guys in the industry handle this? Thanks!

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  • jQuery: How to reverse sortable('serialize') arrays from last to first?

    - by Binyamin
    The discussion begins http://stackoverflow.com/questions/654535/jquery-what-to-do-with-the-list-that-sortableserialize-returns/2920760#2920760 How to reverse it from last to first, updateList.php?id[]=5&id[]=4&id[]=3&id[]=2&id[]=1&&action=update? <ul> <li id="oreder-5">5</li> <li id="oreder-4">4</li> <li id="oreder-3">3</li> <li id="oreder-2">2</li> <li id="oreder-1">1</li> <ul> My code: $(document).ready(function(){ order=[]; $('#list ul').children('li').each(function(idx, elm) { order.push(elm.id.split('-')[1]) }); $.post('updateList.php', {'order[]': order, action: 'update'}); function slideout(){ setTimeout(function(){ $("#response").slideUp("slow", function () {}); }, 2000); } $("#response").hide(); $(function() { $("#list ul").sortable({ opacity: 0.8, cursor: 'move', update: function() { var order = $(this).sortable("serialize") + '&action=update'; $.post("updateList.php", order, function(theResponse){ $("#response").html(theResponse); $("#response").slideDown('slow'); slideout(); }); }}); }); });

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  • Better language or checking tool?

    - by rwallace
    This is primarily aimed at programmers who use unmanaged languages like C and C++ in preference to managed languages, forgoing some forms of error checking to obtain benefits like the ability to work in extremely resource constrained systems or the last increment of performance, though I would also be interested in answers from those who use managed languages. Which of the following would be of most value? A language that would optionally compile to CLR byte code or to machine code via C, and would provide things like optional array bounds checking, more support for memory management in environments where you can't use garbage collection, and faster compile times than typical C++ projects. (Think e.g. Ada or Eiffel with Python syntax.) A tool that would take existing C code and perform static analysis to look for things like potential null pointer dereferences and array overflows. (Think e.g. an open source equivalent to Coverity.) Something else I haven't thought of. Or put another way, when you're using C family languages, is the top of your wish list more expressiveness, better error checking or something else? The reason I'm asking is that I have a design and prototype parser for #1, and an outline design for #2, and I'm wondering which would be the better use of resources to work on after my current project is up and running; but I think the answers may be useful for other tools programmers also. (As usual with questions of this nature, if the answer you would give is already there, please upvote it.)

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  • Populate table fields on query execution

    - by Jason
    I'm trying to build an ASP site that populates a Table based on the results of a selection in a ListBox. In order to do this, I've created a GridView table inside a div element. Currently the default behavior is to show all the items in the specified table in sortable order. However, I'd like to refine this further to allow for display of matches based on the results from the ListBox selection, but am not sure how to execute this. The ListBox fires off a OnSelectionChanged event to the method defined below and the GridView element is defined as <asp:GridView ID="dataListings" runat="server" AllowSorting="True" AutoGenerateColumns="False" DataSourceID="LinqDataSource1" OnDataBinding="ListBox1_SelectedIndexChanged"> protected void ListBox1_SelectedIndexChanged(object sender, EventArgs e) { int itemSelected = selectTopics.SelectedIndex; string[] listing = null; switch (itemSelected)//assign listing the array of course numbers { case 0: break; case 1: listing = arts; break; case 2: listing = currentEvents; break; .... More cases here default: listing = arts; break; } using (OLLIDBDataContext odb = new OLLIDBDataContext()) { var q = from c in odb.tbl_CoursesAndWorkshops where listing.Contains(c.tbl_Course_Description.tbl_CoursesAndWorkshops.course_workshop_number) select c; dataListings.DataSource = q; dataListings.DataBind(); } } However, this method never gets fired. I can see a request being made when changing the selection, but setting a breakpoint at the method declaration does nothing at all. Based on this, setup, I have three related questions What do I need to modify to get the OnSelectionChanged event handler to fire? How can I alter the GridView area to be empty on page load? How do I send the results from the dataListings.DataBind() execution to show in the GridView?

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  • Rails Heroku Gemfile.lock error - push rejected (open source)

    - by KJ50
    I am trying to push my open source RoR application to Heroku but I'm having an issue making the initial push. I have read many similar questions, but none of those answers has helped to solve my problem. I have tried bundle update and bundle install various times. I also have tried removing and then re-committing my Gemfile.lock file, however I get this same error still... $ git push heroku master Counting objects: 5199, done. Compressing objects: 100% (3086/3086), done. Writing objects: 100% (5199/5199), 4.57 MiB | 131 KiB/s, done. Total 5199 (delta 3418), reused 3152 (delta 1962) -----> Removing .DS_Store files -----> Ruby app detected -----> Compiling Ruby/NoLockfile ! ! Gemfile.lock required. Please check it in. ! ! Push rejected, failed to compile Ruby app To [email protected]:frozen-springs-4725.git ! [remote rejected] master -> master (pre-receive hook declined) error: failed to push some refs to '[email protected]:frozen-springs-4725.git' Since my application uses MongoDB with MongoMapper, I suspect that I have some configuration incorrect. My code can be found here on Github (I'm currently working on the heroku branch). Feel free to clone our repository and try it yourself. If anyone has any insight which could help me resolve this issue I would be very thankful!

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  • Getting tree construction with ANTLR

    - by prosseek
    As asked and answered in http://stackoverflow.com/questions/2999755/removing-left-recursion-in-antlr , I could remove the left recursion E - E + T|T T - T * F|F F - INT | ( E ) After left recursion removal, I get the following one E - TE' E' - null | + TE' T - FT' T' - null | * FT' Then, how to make the tree construction with the modified grammar? With the input 1+2, I want to have a tree ^('+' ^(INT 1) ^(INT 2)). Or similar. grammar T; options { output=AST; language=Python; ASTLabelType=CommonTree; } start : e - e ; e : t ep - ??? ; ep : | '+' t ep - ??? ; t : f tp - ??? ; tp : | '*' f tp - ??? ; f : INT | '(' e ')' - e ; INT : '0'..'9'+ ; WS: (' '|'\n'|'\r')+ {$channel=HIDDEN;} ;

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  • filling colors on a map - PHP

    - by jeremy
    I am trying to determine how to fill colors onto a map - such as the "Risk" board game map. I've done this before with HTML tables, by pulling an HTML color code from a SQL table and then just using it to fill the cell the color I want it. But for a non-square map, I'm not sure where to look. I have created a very simple two color map - its white with black borders. My desired result is having the 'regions' on the map shaded with a color, based on data in a sql table (just like the "fill" button in Paint). This looks like what I need: http://php.net/manual/en/function.imagefilltoborder.php and now.. how to define the borders... At the moment I have tried nothing, because the question was: how do I have PHP fill parts of an image? I have tried making an image in Paint, and then scratching my head wondering how to fill parts of it. Having stumbled upon a link, let me focus this a bit more: It appears that with imagefilltoborder that I can put an image on my server, perhaps one that looks like a black and white version of the RISK map - black borders and white everything else. Some questions: Is it correct that the 'border' variable should use the color of my border (whatever value black is) so that the code can "see" where the border is? Is it correct that I'll just need to figure out X,Y coords to begin the fill? Does this work if I have 10 different spots to fill on the map? Can I use varying colors from code or pulled from SQL to assign different colors to those 10 spots, and use 10 different X,Y coords to get them all?

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  • Faster Insertion of Records into a Table with SQLAlchemy

    - by Kyle Brandt
    I am parsing a log and inserting it into either MySQL or SQLite using SQLAlchemy and Python. Right now I open a connection to the DB, and as I loop over each line, I insert it after it is parsed (This is just one big table right now, not very experienced with SQL). I then close the connection when the loop is done. The summarized code is: log_table = schema.Table('log_table', metadata, schema.Column('id', types.Integer, primary_key=True), schema.Column('time', types.DateTime), schema.Column('ip', types.String(length=15)) .... engine = create_engine(...) metadata.bind = engine connection = engine.connect() .... for line in file_to_parse: m = line_regex.match(line) if m: fields = m.groupdict() pythonified = pythoninfy_log(fields) #Turn them into ints, datatimes, etc if use_sql: ins = log_table.insert(values=pythonified) connection.execute(ins) parsed += 1 My two questions are: Is there a way to speed up the inserts within this basic framework? Maybe have a Queue of inserts and some insertion threads, some sort of bulk inserts, etc? When I used MySQL, for about ~1.2 million records the insert time was 15 minutes. With SQLite, the insert time was a little over an hour. Does that time difference between the db engines seem about right, or does it mean I am doing something very wrong?

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  • Android: How to periodically check current location without draining the battery

    - by uyahalom
    I have a background service which works periodically by timer.scheduleAtFixedRate. It wakes up every amount of time (let's say 60 seconds for example) and checks for the location. The location is checked by locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 60000, 5, listener); and the actual location is collected from the listener's onLocationChanged. Now, when the phone is outside and GPS reception is good, this works fine. But, if the phone is inside, the GPS is almost always active - looking for a signal, and the battery is drained rapidly. I created another thread using a Handler and a Runnable in order to conrol the GPS active time accurately: I used locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, listener); and locManager.removeUpdates(listener); so I can open and close the GPS as I want. In this case, I can open the GPS for the exact amount of time, but found out that it doesn't lock in an area with good reception even after 10 seconds. So here I'm draining the battery again... I'm using API level 7, hence I cannot use locationManager.requestSingleUpdate. I have two questions: Is there any way to optimize this process? Will upgrading to API level 9 (and use locationManager.requestSingleUpdate) improve the process significantly? I mean, does it worth upgrading?

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  • Random syntactical error in my php code that I can't find

    - by user348538
    Ordinarily I hate coming here with newbie code questions but nobody can find the error with this code. Maybe you guys can :-) <?php defined('SYSPATH') or die('No direct script access.'); /** * to interact with photos * * @author Max Padraig Wolfgang Bucknell-Leahy */ class Model_Photos { private $apiKey = '12664498208a1380fe49fb1b5a238ef0'; private $secret = '03d43dee65a34513'; private $perms = 'read'; private $sigString = 'test'; private $apiSig = md5($_sigString); private $authArray = array('api_key' => $apiKey, 'perms' => $perms, 'api_sig' => $apiSig); private $authArrayImploded = implode('&', $authArray); private $authLink = 'http://www.flickr.com/services/auth/?' . $authArrayImploded; public function get_photos($number = 5) { if(file_exists(APPPATH . 'cache/main_cache.xml') { echo $authLink; } else { echo 'not so good'; /** */ } } } $class = new Model_Photos; $class->get_photos; the error is: Parse error: syntax error, unexpected '(', expecting ',' or ';' in /home/p14s9nnd/public_html/testing.php on line 15 Thank you in advance and sorry Regards, Max

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  • Drupal module for complex hours of operation / office hours

    - by Eronarn
    Background: I am building a website in Drupal that links together a wide variety of social service providers for the purposes of discovery, collaboration, and all that good stuff. The goal is to make a website that is simple to browse for consumers of these services and simple to update for providers of these services. The beta has been very well received, but I want to switch to a different information schema before the site goes live. Specific question: I am looking for a module (or other solution) that... Stores this data in Drupal (i.e., no GCal) Supports a wide variety of repeats Is intuitive for people editing the node (no Cron-style interfaces, please!) I have looked into several modules on drupal.org and none seem to meet all of these criteria. I've also searched here, and while this question is similar: http://stackoverflow.com/questions/2794149/drupal-create-a-node-with-employee-working-hours my needs are too complex for the offered solution. Some of these providers have "hours" such as "the third Wednesday of every month", or "open during Winter months", or separate hotline & office hours. Likewise, the Date Repeat module doesn't cut it as stands currently. I'm comfortable hacking what I need into an existing module - I just don't want to duplicate effort! If you have a suggestion on what module might be a good starting point, I'd appreciate that input, too. Thanks. <3

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  • Dimension Reduction in Categorical Data with missing values

    - by user227290
    I have a regression model in which the dependent variable is continuous but ninety percent of the independent variables are categorical(both ordered and unordered) and around thirty percent of the records have missing values(to make matters worse they are missing randomly without any pattern, that is, more that forty five percent of the data hava at least one missing value). There is no a priori theory to choose the specification of the model so one of the key tasks is dimension reduction before running the regression. While I am aware of several methods for dimension reduction for continuous variables I am not aware of a similar statical literature for categorical data (except, perhaps, as a part of correspondence analysis which is basically a variation of principal component analysis on frequency table). Let me also add that the dataset is of moderate size 500000 observations with 200 variables. I have two questions. Is there a good statistical reference out there for dimension reduction for categorical data along with robust imputation (I think the first issue is imputation and then dimension reduction)? This is linked to implementation of above problem. I have used R extensively earlier and tend to use transcan and impute function heavily for continuous variables and use a variation of tree method to impute categorical values. I have a working knowledge of Python so if something is nice out there for this purpose then I will use it. Any implementation pointers in python or R will be of great help. Thank you.

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  • Keeping track of dependency revisions

    - by Samaursa
    I have a project with several dependencies that are in various repositories. Each time I commit changes to my project, I make sure I write the revision numbers of all the dependent repositories so that in the event I ever have to come back to this revision (let's call it 5), I can immediately know which revisions of the dependent repositories revision 5 is guaranteed to work with, update the dependencies to the specified revisions, compile and run the project. So for example if I have: Dep1 @ Revisions 10 Dep2 @ Revisions 20 Dep3 @ Revisions 10 Proj @ Revisions 35 And let's say that when Proj was on revision 17, the Dep1 revision was 5, Dep2 revision was 13 and Dep3 revision was 3. So in my SVN logs, I recorded something like this: !! Works with Dep1 Rev 5, Dep2 Rev 13, Dep3 Rev 3 To me this seems primitive and makes me believe that there is a better way to do it. Now in one of my other questions, Ivy Dependency Manager has been recommended. I have not looked at it in detail yet (seems complicated and yet another thing I must learn). To me it seems like the log of SVN (and Mercurial etc.) could have been split into Log and Dependencies (if any) where the latter could be switched off if there were no dependencies (unless of course I am unaware of an easier/better solution). This would allow for a cleaner log that maybe even warned at each new commit to check the previously defined dependencies again and make sure they have not changed. So, I was wondering how everyone manages this situations and if you have any tips, techniques, programs, suggestions that you can offer. Thank you.

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  • What does the Kernel Virtual Memory of each process contain?

    - by claws
    When say 3 programs (executables) are loaded into memory the layout might look something like this: I've following questions: Is the concept of Virtual Memory limited to user processes? Because, I am wondering where does the Operating System Kernel, Drivers live? How is its memory layout? I know its operating system specific make your choice (windows/linux). They say, on a 32 bit machine in a 4GB address space. Half of it (or more recently 1GB) is occupied by kernel. I can see in this diagram that "Kernel Virtual memory" is occupying 0xc0000000 - 0xffffffff (= 1 GB). Are they talking about this? or is it something else? Just want to confirm. What exactly does the Kernel Virtual Memory of each of these processes contain? What is its layout? When we do IPC we talk about shared memory. I don't see any memory shared between these processes. Where does it live? Resources (files, registries in windows) are global to all processes. So, the resource/file handle table must be in some global space. Which area would that be in? Where can I know more about this kernel side stuff.

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  • How to catch unintentional function interpositioning with GCC?

    - by SiegeX
    Reading through my book Expert C Programming, I came across the chapter on function interpositioning and how it can lead to some serious hard to find bugs if done unintentionally. The example given in the book is the following: my_source.c mktemp() { ... } main() { mktemp(); getwd(); } libc mktemp(){ ... } getwd(){ ...; mktemp(); ... } According to the book, what happens in main() is that mktemp() (a standard C library function) is interposed by the implementation in my_source.c. Although having main() call my implementation of mktemp() is intended behavior, having getwd() (another C library function) also call my implementation of mktemp() is not. Apparently, this example was a real life bug that existed in SunOS 4.0.3's version of lpr. The book goes on to explain the fix was to add the keyword static to the definition of mktemp() in my_source.c; although changing the name altogether should have fixed this problem as well. This chapter leaves me with some unresolved questions that I hope you guys could answer: Should our software group adopt the practice of putting the keyword static in front of all functions that we don't want to be exposed? Does GCC have a way to warn about function interposition? We certainly don't ever intend on this happening and I'd like to know about it if it does. Can interposition happen with functions introduced by static libraries? Thanks for the help.

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  • mysql get table based on common column between two tables

    - by Zentdayn
    while trying to learn sql i came across "Learn SQL The Hard Way" and i started reading it. Everything was going fine then i thought ,as a way to practice, to make something like given example in the book (example consists in 3 tables pet,person,person_pet and the person_pet table 'links' pets to their owners). I made this: report table +----+-------------+ | id | content | +----+-------------+ | 1 | bank robbery| | 2 | invalid | | 3 | cat on tree | +----+-------------+ notes table +-----------+--------------------+ | report_id | content | +-----------+--------------------+ | 1 | they had guns | | 3 | cat was saved | +-----------+--------------------+ wanted result +-----------+--------------------+---------------+ | report_id | report_content | report_notes | +-----------+--------------------+---------------+ | 1 | bank robbery | they had guns | | 2 | invalid | null or '' | | 3 | cat on tree | cat was saved | +-----------+--------------------+---------------+ I tried a few combinations but no success. My first thought was SELECT report.id,report.content AS report_content,note.content AS note_content FROM report,note WHERE report.id = note.report_id but this only returns the ones that have a match (would not return the invalid report). after this i tried adding IF conditions but i just made it worse. My question is, is this something i will figure out after getting past basic sql or can this be done in simple way? Anyway i would appreciate any help, i pretty much lost with this. Thank you. EDIT: i have looked into related questions but havent yet found one that solves my problem. I probably need to look into other statements such as join or something to sort this out.

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