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  • switching C compiler causes: Error Initializer cannot be specified for a flexible array member

    - by user1054210
    I am trying to convert our code from one IDE to be used in a different one. The current one uses gcc which allows for this structure to be initialized from a variable array. The new tool does not use gcc gives me an error "Initializer cannot be specified for a flexible array member". So can someone help me understand how to set this up? Should I set up a blank array of variable size and then somewhere assign the #define array as seen below? Here would be an example of the code…(this is current implementation current IDE) In one header file that is Build switchable so we can build this on different hardware platforms we have the following #define #define GPIOS \ /* BANK, PIN, SPD, MODE,… */ GPIOINIT( A, 0, 2, AIN, …) \ GPIOINIT( A, 1, 2, AIN, …) \ GPIOINTINIT(A, 2, 2, AIN, …) \ . . . Then in a different header file that is used in all builds we have PLATFORM_CONFIG_T g_platformConfig = { .name = {PLATFORM_NAME}, (bunch of other stuff), .allGpios = { GPIOS /* here I get the error */ }, }; So I am thinking I can make the error line a variable array and assign to it later in some other way? The problem is the actual array "GPIO" is of different types and pin orders on different designs are different.

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  • How to determine if the camera button is half pressed

    - by Matthew
    I am creating a small test camera application, and I would like to be able to implement a feature that allows focus text bars to be present on the screen while the hardware camera button is pressed half way down. I created a camera_ButtonHalfPress event to perform the focus action, but I am unsure of how to toggle the text bars I would like to show on the screen accordingly. Essentially, my goal would be to show the text bars while the camera button is pressed half way down, and then remove them if the button is pressed all the way or the button is released before being pressed all the way down. The button being released is the part I am having trouble with. What I have is as follows: MainPage.xaml.cs private void camera_ButtonHalfPress(object sender, EventArgs e) { //camera.Focus(); // Show the focus brackets. focusBrackets.Visibility = Visibility.Visible; } } private void camera_ButtonFullPress(object sender, EventArgs e) { // Hide the focus brackets. focusBrackets.Visibility = Visibility.Collapsed; camera.CaptureImage(); } } Currently, if the the user decides to release the camera button before it is pressed all the way, the focus brackets persist on the screen. How might I fix this issue?

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  • Alternative or succesor to GDBM

    - by Anon Guy
    We a have a GDBM key-value database as the backend to a load-balanced web-facing application that is in implemented in C++. The data served by the application has grown very large, so our admins have moved the GDBM files from "local" storage (on the webservers, or very close by) to a large, shared, remote, NFS-mounted filesystem. This has affected performance. Our performance tests (in a test environment) show page load times jumping from hundreds of milliseconds (for local disk) to several seconds (over NFS, local network), and sometimes getting as high as 30 seconds. I believe a large part of the problem is that the application makes lots of random reads from the GDBM files, and that these are slow over NFS, and this will be even worse in production (where the front-end and back-end have even more network hardware between them) and as our database gets even bigger. While this is not a critical application, I would like to improve performance, and have some resources available, including the application developer time and Unix admins. My main constraint is time only have the resources for a few weeks. As I see it, my options are: Improve NFS performance by tuning parameters. My instinct is we wont get much out of this, but I have been wrong before, and I don't really know very much about NFS tuning. Move to a different key-value database, such as memcachedb or Tokyo Cabinet. Replace NFS with some other protocol (iSCSI has been mentioned, but i am not familiar with it). How should I approach this problem?

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  • What happens to existing workspaces after upgrading to TFS 2010

    - by e-mre
    Hi, I was looking for some insight about what happens to existing workspaces and files that are already checked-out on people, after an upgrade to TFS2010. Surprisingly enough I can not find any satisfactory information on this. (I am talking about upgrading on new hardware by the way. Fresh TFS instance, upgraded databases) I've checked TFS Installation guide, I searched through the web, all I could find is upgrade scenarios for the server side. Nobody even mentions what happens to source control clients. I've created a virtual machine to test the upgrade process, The upgrade was successful and all my files and workspaces exist in the new server too. The problem is: The new TFS installation has a new instanceID. When I redirected on the clients to the new server, the client seemed unable to match files and file states in the workspace with the ones on the new server. This makes me wonder if it will be possible to keep working after the production upgrade. As I mentioned above I can not find anything on this, it would be great if anyone could point me to some paper or blog post about this. Thanks in advance...

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  • mmap only needed pages of kernel buffer to user space

    - by axeoth
    See also this answer: http://stackoverflow.com/a/10770582/1284631 I need something similar, but without having to allocate a buffer: the buffer is large, in theory, but the user space program only needs to access some parts of it (it mocks some registers of a hardware). As I cannot allocate with vmalloc_user() such a large buffer (kernel 32 bit, in embedded environment, no swap...), I followed the same approach as in the quoted answer, trying to allocate only those pages that are really requested by the user space. So: I use a my_mmap() function for the device file (actually, is the .mmap field of a struct uio_info) to set up the fields of the vma, then, in the vm_area_struct's .fault field (also named my_fault()), I should return a page. except that: In the my_fault() method of vm_area_struct, I cannot obtain a page through: vmf->page=vmalloc_to_page(my_buf + (vmf->pgoff << PAGE_SHIFT)); since there is no allocated buffer: my_buf = vmalloc_user(MY_BUF_SIZE); fails with "allocation failed: out of vmalloc space - use vmalloc= to increase size." (and there is no room or swap to increase that vmalloc= parameter). So, I would need to get a page from the kernel and fill the vmf->page field. How to allocate a page (I assume that the offset of the page is known, as it is vm->pgoff). What base memory should I use instead of my_buf? PS: I also did set up the vma->flags |= VM_NORESERVE; (in the my_mmap()), but not sure if it helps. Is there any vmalloc_user_unreserved()-like function? (let's say, lazy allocation) Also, writing 1 to /proc/sys/vm/overcommit_memory and large values (eg 500) to /proc/sys/vm/overcommit_ratio before trying to my_buf=vmalloc_user(<large_size>) didn't work.

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  • How should I configure grub for booting linux kernel from a USB hard drive?

    - by skolima
    I have a laptop hard drive in an external enclosure which I use as a large pendrive. For an added twist, I have installed Linux on it, so I can boot any machine with my distribution of choice (e.g. for data recovery or repairing a b0rked system or just using a borrowed laptop without destroying the preinstalled Windows). The problem is that, depending on the hardware configuration, the USB hard drive may be visible under different paths. For grub configuration I just use (hda0,0) as it is relative to the device the grub was launched from. I have UUID entries in /etc/fstab. I also specify rootwait in the kernel parameters so that it waits for the USB subsystem to settle down before trying to mount the device. What should I pass to the kernel as root= ? Currently boot from the pendrive once, check the debug messages to see what /dev/sdX device has been assigned to the USB drive by the kernel, then reboot and edit the grub configuration. I can't change anything on the PC besides enabling Boot from USB hard drive in BIOS and setting it to higher priority than internal hard drives. There are various initrd generating scripts which include support for UUID in root device path, unfortunately the Gentoo native one (genkernel) does not support rootwait and I had no luck trying to use others. The boot process goes like this (it is quite similar in Windows): The BIOS chooses the boot device and loads whatever is its MBR (which happens to be grub stage-1). Grub loads it's configuration and stage-2 files from device it has set as root, using (hd0) for the device it was loaded from by BIOS. Grub loads and starts a kernel (still the same numbering, so I can use (hd0,0) again ). Kernel initializes all built-in devices (rootwait does it's magic now). Kernel mounts the partition it was passed as root (this is a kernel parameter, not grub parameter). init.d starts the userland booting process, including mounting things from /etc/fstab. Part 5 is the one giving me problems.

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  • Is it possible to send OSC commands to an iPad via the Camera Connection Kit?

    - by HELVETICADE
    I'm building a small controller device that I'd like to partner with a computer. I've settled on using OSC out from my custom built hardware and am pretty satisfied with what I can get from WOscLib. Two goals I'd like to achieve are portability and a very nice ratio between battery:computing power, and this has lured me towards using iPhoneOS to accomplish my goals. I think the iPad would suit my needs perfectly, except that using wifi to broadcast OSC out from my device requires that device to be connected to a third device with a wifi chip, and this would destroy the goal of portability, whilst also introducing potential latency and stability headaches. My question is pretty simple: Can I push OSC commands FROM my controller TO an iPad via USB and the Camera Connection Kit? If I could accomplish this, the two major goals of my project would be fulfilled very nicely. This seems like it should be a simple little question, but researching this obsessively over the past few weeks has left me more almost more uncertain than if I had done no research at all. I'd really like some more confidence before I go down this route, and it seems like it should be possible. Any insight would be very, very appreciated.

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  • What about race condition in multithreaded reading?

    - by themoob
    Hi, According to an article on IBM.com, "a race condition is a situation in which two or more threads or processes are reading or writing some shared data, and the final result depends on the timing of how the threads are scheduled. Race conditions can lead to unpredictable results and subtle program bugs." . Although the article concerns Java, I have in general been taught the same definition. As far as I know, simple operation of reading from RAM is composed of setting the states of specific input lines (address, read etc.) and reading the states of output lines. This is an operation that obviously cannot be executed simultaneously by two devices and has to be serialized. Now let's suppose we have a situation when a couple of threads access an object in memory. In theory, this access should be serialized in order to prevent race conditions. But e.g. the readers/writers algorithm assumes that an arbitrary number of readers can use the shared memory at the same time. So, the question is: does one have to implement an exclusive lock for read when using multithreading (in WinAPI e.g.)? If not, why? Where is this control implemented - OS, hardware? Best regards, Kuba

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  • Database structure for ecommerce site

    - by imanc
    Hey Guys, I have been tasked with designing an ecommerce solution. The aspect that is causing me the most problems is the database. Currently the site consists of 10+ country based shops each with their own database (all residing on the same mysql instance). For the new site I'd rather all these shop databases be merged into one database so that all tables (products, orders, customers etc.) have a shop_id field. From a programming perspective this seems to make the most sense as we won't have to manage data across multiple databases. Currently the entire site generates about 120k orders a year, but is experiencing fairly heavy growth and we need to design a solution that will scale. In 5 years there may be more than a million orders per year and a database that contains 5 years order history (archiving maybe a solution here). The question is - do we use a single database, or do we keep the database-per-shop structure? I am currently trying to find supporting evidence for either avenue. The company I am designing the solution for prefer the per-shop database structure because they believe it will allow the sites to scale. But my argument is that the shop's database probably won't get that busy over the next few years that they exceed the capacity of a mysql database and a "no expenses spared" hardware set-up. I am wondering if anyone has any advice either way? Does anyone have experience with websites / ecommerce sites that have tables containing millions of records? I know there is probably not a clear answer here, but at what stage do we have too many records or too large table files to have a fast loading site? Also, if anyone has any advice on sources of information - books, websites, etc. where I can do further research, it would be highly appreciated! Cheers, imanc

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  • C# generics when T could be an array

    - by bufferz
    I am writing a C# wrapper for a 3rd party library that reads both single values and arrays from a hardware device, but always returns an object[] array even for one value. This requires repeated calls to object[0] when I'd like the end user to be able to use generics to receive either an array or single value. I want to use generics so the callee can use the wrapper in the following ways: MyWrapper<float> mw = new MyWrapper<float>( ... ); float value = mw.Value; //should return float; MyWrapper<float[]> mw = new MyWrapper<float[]>( ... ); float[] values = mw.Value; //should return float[]; In MyWrapper I have the Value property currently as the following: public T Value { get { if(_wrappedObject.Values.Length > 1) return (T)_wrappedObject.Value; //T could be float[]. this doesn't compile. else return (T)_wrappedObject.Values[0]; //T could be float. this compiles. } } I get a compile error in the first case: Cannot convert type 'object[]' to 'T' If I change MyWrapper.Value to T[] I receive: Cannot convert type 'object[]' to 'T[]' Any ideas of how to achieve my goal? Thanks!

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  • What technologies/tools do people use to implement live websites ?

    - by MadSeb
    Hi, I have the following situation: -I have a server A hooked up to a piece of hardware that sends values and information out of every second. Programs on the server machine can read these values. This server A is in a very remote location so Internet connection is very slow and not reliable but the connection does exist. Let's say it's a weather station in the Arctic. -Users from the home location want to monitorize the weather values somehow. Well, the users can use a remote desktop connection the server A but that would be too too slow. My idea is somehow to have a website on a web server (let's call the webserver - B and B is in a home location ) and make the server A connect to the server B and somehow send values and the web application reads the values and displays them....... but how to do such a system ?? I know I can use MySQL and have the server A connect to a SQL server on server B and send INSERT queries and have the web application running on server B constantly read from the SQL server but I think that would be way way too slow and I think there has to be a better solution. Any ideas ? BTW. The users should be able to send information to the weather station from the website as well ( so an ADMIN user should be allowed to shut down the weather station from the website or whatever) Best regards, MadSeb

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  • Tracking down slow managed DLL loading

    - by Alex K
    I am faced with the following issue and at this point I feel like I'm severely lacking some sort of tool, I just don't know what that tool is, or what exactly it should be doing. Here is the setup: I have a 3rd party DLL that has to be registered in GAC. This all works fine and good on pretty much every machine our software was deployed on before. But now we got 2 machines, seemingly identical to the ones we know work (they are cloned from the same image and stuffed with the same hardware, so pretty much the only difference is software settings, over which I went over and over, and they seem fine). Now the problem, the DLL in GAC takes a very long time to load. At least I believe this is the issue, what I can say definitively is that instantiating a single class from that DLL is the slow part. Once it is loaded, thing fly as they always have. But while on known-good machines the DLL loads so fast that a timestamp in the log doesn't even change, on these 2 machines it take over 1min to load. Knowns: I have no access to the source, so I can't debug through the DLL. Our app is the only one that uses it (so shouldn't be simultaneous access issues). There is only one version of this DLL in existance, so it shouldn't be a matter of version conflict. The GAC reference is being used (if I uninstall the DLL from GAC, an exception will be thrown about the missing GAC reference). Could someone with a greater skill in debug-fu suggest what I can do to track down the root cause of this issue?

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  • Real time location tracking - windows program or browser based?

    - by mawg
    I want to track a few hundred, maybe a few thousand people in real time. Let's say that the hardware aspects are sorted out and I can get the data into a database. Now, I want to get it out and show it, in real-time. Weeeell ... "real-enough" time. Let's say that I want to draw a floorplan of a building and plot everyone every 1 to 5 seconds. (I might want to show only certain "kinds" of people at the click of a button; I will need datamining, etc, but let's stick with the worse case scenario). I am comfortable enough with PHP, though not this sort of thing. I personally would be happier with a windows app coded in Delphi, but the trend seems to be to make everything browser based. So, the question, I guess is whether a browser can handle this and whether there are compelling arguments for a windows-based or browser-based solution. If browser-based can handle this (displaying a few thousand data-points a second), and there are no overwhelming arguments for windows then I guess I will go for browser-based and learn a few new tricks. The obvious advantage being that I could also re-use a large part of my code for (vehicle) tracking on Google maps.

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  • Can i change the view without changing the controller?

    - by Ian Boyd
    Pretend1 there is a place to type in a name:     Name: __________________ When the text box changes, the value is absorbed into the controller, who stores it in data model. Business rules require that a name be entered: if there is no text entered the TextBox should be colored something in the view to indicate baddness; otherwise it can be whatever color the view likes. The TextBox contains a String, the controller handles a String, and the model stores a String. Now lets say i want to improve the view. There is a new kind of text box2 that can be fed not only string-based keyboard input, but also an image. The view (currently) knows how to determine if the image is in the proper format to perform the processing required to extract text out of it. If there is text, then that text can be fed to the controller, who feeds it to the data model. But if the image is invalid, e.g.3 wrong file format invalid dimensions invalid bit depth unhandled or unknown encoding format missing or incorrectly located registration marks contents not recognizable the view can show something to the user that the image is bad. But the telling the user that something is bad is supposed to be the job of the controller. i'm, of course, not going to re-write the controller to handle Image based text-input (e.g. image based names). a. the code is binary locked inside a GUI widget4 b. there other views besides this one, i'm not going to impose a particular view onto the controller c. i just don't wanna. If i have to change things outside of this UI improvement, then i'll just leave the UI unimproved5 So what's the thinking on having different views for the same Model and Controller? Nitpicker's Corner 1 contrived hypothetical example 2 e.g. bar code, g-mask, ocr 3 contrived hypothetical reasons 4 or hardware of a USB bar-code scanner 5 forcing the user to continue to use a DateTimePicker rather than a TextBox

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  • How I May Have Taken A Wrong Path in Programming

    - by Ygam
    I am in a major stump right now. I am a BSIT graduate, but I only started actual programming less than a year ago. I observed that I have the following attitude in programming: I tend to be more of a purist, scorning unelegant approaches to solving problems using code I tend to look at anything in a large scale, planning everything before I start coding, either in simple flowcharts or complex UML charts I have a really strong impulse on refactoring my code, even if I miss deadlines or prolong development times I am obsessed with good directory structures, file naming conventions, class, method, and variable naming conventions I tend to always want to study something new, even, as I said, at the cost of missing deadlines I tend to see software development as something to engineer, to architect; that is, seeing how things relate to each other and how blocks of code can interact (I am a huge fan of loose coupling) i.e the OOP thinking I tend to combine OOP and procedural coding whenever I see fit I want my code to execute fast (thus the elegant approaches and refactoring) This bothers me because I see my colleagues doing much better the other way around (aside from the fact that they started programming since our first year in college). By the other way around I mean, they fire up coding, gets the job done much faster because they don't have to really look at how clean their codes are or how elegant their algorithms are, they don't bother with OOP however big their projects are, they mostly use web APIs, piece them together and voila! Working code! CLients are happy, they get paid fast, at the expense of a really unmaintainable or hard-to-read code that lacks structure and conventions, or slow executions of certain actions (which the common reasoning against would be that internet connections are much faster these days, hardware is more powerful). The excuse I often receive is clients don't care about how you write the code, but they do care about how long you deliver it. If it works then all is good. Now, did my "purist" approach to programming may have been the wrong way to start programming? Should I just dump these purist concepts and just code the hell up because I have seen it: clients don't really care how beautifully coded it is?

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  • Negative number representation across multiple architechture

    - by Donotalo
    I'm working with OKI 431 micro controller. It can communicate with PC with appropriate software installed. An EEPROM is connected in the I2C bus of the micro which works as permanent memory. The PC software can read from and write to this EEPROM. Consider two numbers, B and C, each is two byte integer. B is known to both the PC software and the micro and is a constant. C will be a number so close to B such that B-C will fit in a signed 8 bit integer. After some testing, appropriate value for C will be determined by PC and will be stored into the EEPROM of the micro for later use. Now the micro can store C in two ways: The micro can store whole two byte representing C The micro can store B-C as one byte signed integer, and can later derive C from B and B-C I think that two's complement representation of negative number is now universally accepted by hardware manufacturers. Still I personally don't like negative numbers to be stored in a storage medium which will be accessed by two different architectures because negative number can be represented in different ways. For you information, 431 also uses two's complement. Should I get rid of the headache that negative number can be represented in different ways and accept the one byte solution as my other team member suggested? Or should I stick to the decision of the two byte solution because I don't need to deal with negative numbers? Which one would you prefer and why?

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  • How difficult is it for an old-school programmer to pick up an FPGA kit and make something useful wi

    - by JUST MY correct OPINION
    I'm an old, old, old coder. (How old? I've used paper tape in anger.) I've programmed in a lot of languages and under a lot of paradigms (spaghetti, structured, object-oriented, functional and a smattering of logical). I'm getting bored. FPGAs look interesting to me. I have the crazy notion of resurrecting some of the ancient hardware I worked on in the days using FPGAs. I know this can be done because I've seen PDP-10 and PDP-11 implementations in FPGAs. I'd like to do the same for a few machines that are perhaps not as popular as those two, however. While I am an old, old coder, what I am not is an electronics or computer systems engineer. I'll be learning from scratch if I go down this path. My question, therefore, is two-fold: How difficult will it be for this old dinosaur to pick up and learn FPGAs to the point that interesting (not necessarily practical -- more from a hobbyist perspective) projects can be made? What should I start with learning-wise to go down this path? I know where to get FPGA kits, but I haven't found anything like "FPGAs for Complete Dinosaurs" yet anywhere out there.

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  • What's the best Linux backup solution?

    - by Jon Bright
    We have a four Linux boxes (all running Debian or Ubuntu) on our office network. None of these boxes are especially critical and they're all using RAID. To date, I've therefore been doing backups of the boxes by having a cron job upload tarballs containing the contents of /etc, MySQL dumps and other such changing, non-packaged data to a box at our geographically separate hosting centre. I've realised, however that the tarballs are sufficient to rebuild from, but it's certainly not a painless process to do so (I recently tried this out as part of a hardware upgrade of one of the boxes) long-term, the process isn't sustainable. Each of the boxes is currently producing a tarball of a couple of hundred MB each day, 99% of which is the same as the previous day partly due to the size issue, the backup process requires more manual intervention than I want (to find whatever 5GB file is inflating the size of the tarball and kill it) again due to the size issue, I'm leaving stuff out which it would be nice to include - the contents of users' home directories, for example. There's almost nothing of value there that isn't in source control (and these aren't our main dev boxes), but it would be nice to keep them anyway. there must be a better way So, my question is, how should I be doing this properly? The requirements are: needs to be an offsite backup (one of the main things I'm doing here is protecting against fire/whatever) should require as little manual intervention as possible (I'm lazy, and box-herding isn't my main job) should continue to scale with a couple more boxes, slightly more data, etc. preferably free/open source (cost isn't the issue, but especially for backups, openness seems like a good thing) an option to produce some kind of DVD/Blu-Ray/whatever backup from time to time wouldn't be bad My first thought was that this kind of incremental backup was what tar was created for - create a tar file once each month, add incrementally to it. rsync results to remote box. But others probably have better suggestions.

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  • Forwarding HTTP Request with Direct Server Return

    - by Daniel Crabtree
    I have servers spread across several data centers, each storing different files. I want users to be able to access the files on all servers through a single domain and have the individual servers return the files directly to the users. The following shows a simple example: 1) The user's browser requests http://www.example.com/files/file1.zip 2) Request goes to server A, based on the DNS A record for example.com. 3) Server A analyzes the request and works out that /files/file1.zip is stored on server B. 4) Server A forwards the request to server B. 5) Server B returns file1.zip directly to the user without going through server A. Note: steps 4 and 5 must be transparent to the user and cannot involve sending a redirect to the user as that would violate the requirement of a single domain. From my research, what I want to achieve is called "Direct Server Return" and it is a common setup for load balancing. It is also sometimes called a half reverse proxy. For step 4, it sounds like I need to do MAC Address Translation and then pass the request back onto the network and for servers outside the network of server A tunneling will be required. For step 5, I simply need to configure server B, as per the real servers in a load balancing setup. Namely, server B should have server A's IP address on the loopback interface and it should not answer any ARP requests for that IP address. My problem is how to actually achieve step 4? I have found plenty of hardware and software that can do this for simple load balancing at layer 4, but these solutions fall short and cannot handle the kind of custom routing I require. It seems like I will need to roll my own solution. Ideally, I would like to do the routing / forwarding at the web server level, i.e. in PHP or C# / ASP.net. However, I am open to doing it at a lower level such as Apache or IIS, or at an even lower level, i.e. a custom proxy service in front of everything.

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  • How to optimize a postgreSQL server for a "write once, read many"-type infrastructure ?

    - by mhu
    Greetings, I am working on a piece of software that logs entries (and related tagging) in a PostgreSQL database for storage and retrieval. We never update any data once it has been inserted; we might remove it when the entry gets too old, but this is done at most once a day. Stored entries can be retrieved by users. The insertion of new entries can happen rather fast and regularly, thus the database will commonly hold several millions elements. The tables used are pretty simple : one table for ids, raw content and insertion date; and one table storing tags and their values associated to an id. User search mostly concern tags values, so SELECTs usually consist of JOIN queries on ids on the two tables. To sum it up : 2 tables Lots of INSERT no UPDATE some DELETE, once a day at most some user-generated SELECT with JOIN huge data set What would an optimal server configuration (software and hardware, I assume for example that RAID10 could help) be for my PostgreSQL server, given these requirements ? By optimal, I mean one that allows SELECT queries taking a reasonably little amount of time. I can provide more information about the current setup (like tables, indexes ...) if needed.

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  • Should we retire the term "Context"?

    - by MrGumbe
    I'm not sure if there is a more abused term in the world of programming than "Context." A word that has a very clear meaning in the English language has somehow morphed into a hot mess in software development, where the definition where the connotation can be completely different based on what library you happen to be developing in. Tomcat uses the word context to mean the configuration of a web application. Java applets, on the other hand, use an AppletContext to define attributes of the browser and HTML tag that launched it, but the BeanContext is defined as a container. ASP.NET uses the HttpContext object as a grab bag of state - containing information about the current request / response, session, user, server, and application objects. Context Oriented Programming defines the term as "Any information which is computationally accessible may form part of the context upon which behavioral variations depend," which I translate as "anything in the world." The innards of the Windows OS uses the CONTEXT structure to define properties about the hardware environment. The .NET installation classes, however, use the InstallContext property to represent the command line arguments entered to the installation class. The above doesn't even touch how all of us non-framework developers have used the term. I've seen plenty of developers fall into the subconscious trap of "I can't think of anything else to call this class, so I'll name it 'WidgetContext.'" Do you all agree that before naming our class a "Context," we may want to first consider some more descriptive terms? "Environment", "Configuraton", and "ExecutionState" come readily to mind.

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  • Should a C++ constructor do real work?

    - by Wade Williams
    I'm strugging with some advice I have in the back of my mind but for which I can't remember the reasoning. I seem to remember at some point reading some advice (can't remember the source) that C++ constructors should not do real work. Rather, they should initialize variables only. The advice when on to explain that real work should be done in some sort of init() method, to be called separately after the instance was created. The situation is I have a class that represents a hardware device. It makes logical sense to me for the constructor to call the routines that query the device in order to build up the instance variables that describe the device. In other words, once new instantiates the object, the developer receives an object which is ready to be used, no separate call to object-init() required. Is there a good reason why constructors shouldn't do real work? Obviously it could slow allocation time, but that wouldn't be any different if calling a separate method immediately after allocation. Just trying to figure out what gotchas I not currently considering that might have lead to such advice.

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  • MapView EXC_BAD_ACCESS (SIGSEGV) and KERN_INVALID_ADDRESS

    - by user768113
    I'm having some 'issues' with my application... well, it crashes in an UIViewController that is presented modally, there the user enters information through UITextFields and his location is tracked by a MapView. Lets call this view controller "MapViewController" When the user submits the form, I call a different ViewController - modally again - that processes this info and a third one answers accordingly, then go back to a MenuVC using unwinding segues, which then calls MapViewController and so on. This sequence is repeated many times, but it always crashes in MapViewController. Looking at the crash log, I think that the MapView can be the problem of this or some element in the UI (because of the UIKit framework). I tried to use NSZombie in order to track a memory issue but it doesn't give me a clue about whats happening. Here is the crash log Hardware Model: iPad3,4 Process: MyApp [2253] OS Version: iOS 6.1.3 (10B329) Report Version: 104 Exception Type: EXC_BAD_ACCESS (SIGSEGV) Exception Codes: KERN_INVALID_ADDRESS at 0x00000044 Crashed Thread: 0 Thread 0 name: Dispatch queue: com.apple.main-thread Thread 0 Crashed: 0 IMGSGX554GLDriver 0x328b9be0 0x328ac000 + 56288 1 IMGSGX554GLDriver 0x328b9b8e 0x328ac000 + 56206deallocated instance 2 IMGSGX554GLDriver 0x328bc2f2 0x328ac000 + 66290 3 IMGSGX554GLDriver 0x328baf44 0x328ac000 + 61252 4 libGPUSupportMercury.dylib 0x370f86be 0x370f6000 + 9918 5 GLEngine 0x34ce8bd2 0x34c4f000 + 629714 6 GLEngine 0x34cea30e 0x34c4f000 + 635662 7 GLEngine 0x34c8498e 0x34c4f000 + 219534 8 GLEngine 0x34c81394 0x34c4f000 + 205716 9 VectorKit 0x3957f4de 0x394c7000 + 754910 10 VectorKit 0x3955552e 0x394c7000 + 582958 11 VectorKit 0x394d056e 0x394c7000 + 38254 12 VectorKit 0x394d0416 0x394c7000 + 37910 13 VectorKit 0x394cb7ca 0x394c7000 + 18378 14 VectorKit 0x394c9804 0x394c7000 + 10244 15 VectorKit 0x394c86a2 0x394c7000 + 5794 16 QuartzCore 0x354a07a4 0x35466000 + 239524 17 QuartzCore 0x354a06fc 0x35466000 + 239356 18 IOMobileFramebuffer 0x376f8fd4 0x376f4000 + 20436 19 IOKit 0x344935aa 0x34490000 + 13738 20 CoreFoundation 0x33875888 0x337e9000 + 575624 21 CoreFoundation 0x338803e4 0x337e9000 + 619492 22 CoreFoundation 0x33880386 0x337e9000 + 619398 23 CoreFoundation 0x3387f20a 0x337e9000 + 614922 24 CoreFoundation 0x337f2238 0x337e9000 + 37432 25 CoreFoundation 0x337f20c4 0x337e9000 + 37060 26 GraphicsServices 0x373ad336 0x373a8000 + 21302 27 UIKit 0x3570e2b4 0x356b7000 + 357044 28 MyApp 0x000ea12e 0xe9000 + 4398 29 MyApp 0x000ea0e4 0xe9000 + 4324 I think thats all, additionally, I would like to ask you: if you are using unwind segues then you are releasing view controllers from the memory heap, right? Meanwhile, performing segues let you instantiate those controllers. Technically, MenuVC should be the only VC alive in the heap during the app life cycle if you understand me.

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  • Closing Windows Forms on a Touchscreen

    - by drharris
    Our clients have fat fingers, and so do we. We take touchscreen netbooks apart to insert them into our custom hardware, and I write a software interface that shows up on the touchscreen. The problem is that it has about a 3/4" bezel over the screen, which means hitting that little red "X" becomes a challenge, especially considering reduced capacitive ability on the edges and corners. Is there a way to make this standard close button larger? Of course in the application I can always make really nice 80x80 buttons that are perfectly usable, but there seems to be no way to override the default frame of the form. We have tried enabling Large Fonts and all the built-in accessibility features, but nothing seems to make it large enough to hit successfully. Simply adding a toolbar button is also not much of an option. We prefer to utilize the standard look and feel of a normal Windows application. Alternatively, should we be looking at making some sort of "kiosk mode" where we simply go fullscreen and do nothing involving the taskbar or title bar? How difficult is this to accomplish, if so?

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  • Using virtualization infrastructure for J2EE application distribution- viable alternative?

    - by Dan
    Our company builds custom J2EE web solutions. At the moment, we use standard J2EE distribution mechanisms (ear/war archives). Application servers are generally administered by our clients' IT departments and since we do not have complete control over the environment, a lot of entropy can be introduced into the solution. For example: latest app. server patch not applied conflicting third party libraries inside the app. server root server runtime and tuning parameters not configured (for example, number of connections in database pool) We are looking into using virtualization infrastructure for J2EE application distribution. Instead of sending the ear/war archive, we’d send image with application server node and our application preinstalled. Some of the benefits are same as using with using virtualization infrastructure in general, namely better use of hardware resources. For us, it reduces the entropy of hosting infrastructure - distributing VM should be less affected by hosting environment. So far, the downside I see can be in application server licenses, here they will have to use dedicated servers for our solution, but this is generally already done that way. Also, there is a complexity with maintaining virtualization infrastructure, but this is often something IT departments have more experience with than with administering and fine-tuning J2EE solutions. Anyone has experience with this model? What are the downsides? Will we not just replace one type of complexity with other?

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