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  • Is it safe to catch an access violation in this scenario?

    - by Eloff
    I've read a lot, including here on SO that suggests this is a very bad idea in general and that the only thing you can do safely is exit the program. I'm not sure that this is true. This is for a pooling memory allocator that hands off large allocations to malloc. During pool_free() a pointer needs to be checked it it belongs to a pool or was allocated with malloc. By rounding the address down to the nearest 1MB boundary, I get a pointer to the beginning of a block of memory in the pool, or undefined if malloc was used. In the first case I can easily verify that the block of memory belongs to the pool, but, if it does not I will either fail this verification, or I will get an access violation (note that this is a read-only process). Could I not catch this with SEH (Windows) or handle the signal (POSIX) and simply treat it as a failed verification? (i.e. this is only possible if malloc was used, so pass the ptr to free())

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  • Linux Kernel - Slab Allocator Question

    - by Drex
    I am playing around with the kernel and am looking at the kmem_cache files_cachep belonging to fork.c. It detects the sizeof(files_struct). My question is this: I have altered files_struct and added a rb_root (red/black tree root) using the built-in functionality in linux/rbtree.h. I can properly insert values into this tree. However, at some point, a segfault occurs and GDB backtraces the following information: (gdb) backtrace 0 0x08066ad7 in page_ok (page=) at arch/um/os-Linux/sys-i386/task_size.c:31 1 0x08066bdf in os_get_top_address () at arch/um/os-Linux/sys-i386/task_size.c:100 2 0x0804a216 in linux_main (argc=1, argv=0xbfb05f14) at arch/um/kernel/um_arch.c:277 3 0x0804acdc in main (argc=1, argv=0xbfb05f14, envp=0xbfb05f1c) at arch/um/os-Linux/main.c:150 I have spent many hours trying to figure out why there is a segfault given that the red/black tree inserts properly. I'm thinking it's a memory allocation issue with new processes made by fork() of a parent process. Could this be the case and could it have something to do with kmem_cache files_cachep?

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  • Generate multiple graphics from within an R function

    - by William Doane
    I'd like to spawn several graphics windows from within a function in R using ggplot graphics... testf <- function(a, b) { devAskNewPage(TRUE) qplot(a, b); # grid.newpage(recording = TRUE) dev.new() qplot(a, a+a); # grid.newpage(recording = TRUE) dev.new() qplot(b, b+b); } library(ggplot2) x <- rnorm(50) y <- rnorm(50) testf(x, y) However, neither dev.new() nor grid.newpage() seems to flush the preceding plot. I know that, in R, functions normally only produce the last thing they evaluate, but I'd like to understand the process better and to learn of any possible workarounds. Thoughts?

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  • Question regarding built-in type variable is returned from a function

    - by Chan
    Hello, If a local object is returned in a function call, it has to do at least three steps: 1. Copy constructor is called to hold a copy. 2. Destroy local object. 3. A copy is return. For example: x = y + z If x is an integer object. A copy of y + z should be returned, then a new object is created, then assignment operator of x will take this object as parameter. So my question is: Is the same process used for built-in type such as int, double...? If they're not the same, how's it done? Thanks, Chan

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  • Wordpress include custom page

    - by Josef
    Hi, I'm sure this is a simple question. But how do I get Wordpress at startup to ignore trying to load a Page or Post and instead load my custom page? When in the Wordpress bootstrap process is it decided which php-page is going to load? I will have the following url: bt.local/wp/ads/1 And would like a php-page called ads.php to be loaded and load the ad with adid = 1. What's the best way to solve this? (there's no Post called ads and there's no Page called Ads). Thank you! KR Josef

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  • Can "\Device\NamedPipe\\Win32Pipes" handles cause "Too many open files" error?

    - by Igor Oks
    Continuing from this question: When I am trying to do fopen on Windows, I get a "Too many open files" error. I tried to analyze, how many open files I have, and seems like not too much. But when I executed Process Explorer, I noticed that I have many open handles with similar names: "\Device\NamedPipe\Win32Pipes.00000590.000000e2", "\Device\NamedPipe\Win32Pipes.00000590.000000e3", etc. I see that the number of these handles is exactly equal to the number of the iterations that my program executed, before it returned "Too many open files" and stopped. I am looking for an answer, what are these handles, and could they actually cause the "Too many open files" error? In my program I am loading files from remote drive, and I am creating TCP/IP connections. Could one of these operations create these handles?

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  • How to call an external webservice in asp.net

    - by prince23
    hi, i have an webservice written by java application now. i need to use that webservice in my application and send a parameter to it. For example lets say this is the path of the webservice : http://localhost:1838/Ajax/WebService.as now once i click the button in my page[emp.aspx] i need to call the above webservice path 2: what is the use of creating an proxy for an webservice using wsdl tool can anyone tell me the syntax for it? so what is the process i need to follow to consume an webservice written in another applcation or domain looking forward for an solution thank you

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  • Tools and ways to generate HTML help for built-in help system (QtHelp)?

    - by BastiBense
    Hello, I'm in the progress of implementing a built-in help system based on QtHelp into my application. Since QtHelp is based on Qt's help collection files, I need to produce a set of HTML pages. Since I won't be writing the documentation alone (a few of my colleagues will write, too), I am looking for the best way to produce these files. We are internally using a Wiki, and I know that the documentation should be written in some kind of markup language instead of giving all authors a WYSIWYG HTML editor. So my question is, are there tools out there which help with the process of generating documentation that can be exported as a set of HTML files, and possibly, as PDFs, too?. Thanks in advance! Update: I'm already using Doxygen for C++ documentation generation. But I'm not exactly looking for an API-Documentation generator, but something like LaTeX, which allows you to format the documentation contents like a markup document (much like a Wiki).

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  • Is SEO knowledge important for web developers?

    - by splattne
    Looking for some SEO (Search engine optimization) questions on Stackoverflow, I saw ambivalent reactions to these questions. Some were closed as "not programming related" or were downvoted, others were answered and got upvoted. It seems that many developers think SEO was something "dirty" or belonged in the realm of spam. IMHO designing for search engines and practising SEO techniques adds important value to the final product like, for example, a good user interface. Should SEO really be left to specialized non-programmers? Shouldn't web developers have profound SEO knowledge? Or is it okay to apply SEO as a post-development process?

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  • Compressing large text data before storing into db?

    - by Steel Plume
    Hello, I have application which retrieves many large log files from a system LAN. Currently I put all log files on Postgresql, the table has a column type TEXT and I don't plan any search on this text column because I use another external process which nightly retrieves all files and scans for sensitive pattern. So the column value could be also a BLOB or a CLOB, but now my question is the following, the database has already its compression system, but could I improve this compression manually like with common compressor utilities? And above all WHAT IF I manually pre-compress the large file and then I put as binary into the data table, is it unuseful as database system provides its internal compression?

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  • Error in R for missing object

    - by griffin
    I have several nested functions, some of which as called in lapply clauses. In the process, sometimes I don't set a default for a parameter and instead check if it was supplied using the missing function. I'm getting a strange error right now when I'm not passing a value for a parameter, it has no default, yet missing resolves to FALSE. And when I try to use or check the parameter in any other way (using length, exists, etc.), I get an error: Error in try(length(x)) : argument "data" is missing, with no default Has anyone experienced this failure of the missing function before?

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  • Database query optimization

    - by hdx
    Ok my Giant friends once again I seek a little space in your shoulders :P Here is the issue, I have a python script that is fixing some database issues but it is taking way too long, the main update statement is this: cursor.execute("UPDATE jiveuser SET username = '%s' WHERE userid = %d" % (newName,userId)) That is getting called about 9500 times with different newName and userid pairs... Any suggestions on how to speed up the process? Maybe somehow a way where I can do all updates with just one query? Any help will be much appreciated! PS: Postgres is the db being used.

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  • Choosing MooTools over Google closure?

    - by Shekhar
    I am in a process to select javascript library for our new web application. This app is not very UI heavy but has forms, reports, search, calendars, tabs and target multiple countries like most web apps. We are a tiny team. Biggest concern is maintainability and readability of the code. We are Python programmers. After evaluating many other javascript frameworks we have narrowed down to mootools and google-closure. We loved mootools syntax. It took us no time to learn. It's like Python. On other hand we were stumped seeing private/public in google closure. It's tempting to go for mootools however, I would love to hear from you about specific advantages these frameworks offer over each other.

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  • directx 9 hlsl vs. directx 10 hlsl : syntex the same.

    - by numerical25
    For the past month or so I been busting my behind trying to learn directx. So I been mixing back back and fourth from directx 9 to directx 10. One of the major changes I've seen in the two is how to process vectors in the graphics card. one of the drastic changes I notice is how you get the gpu to recognize your structs. In directx 9 you define the Flexible Vertex Formats your typical set up would be like this... #define CUSTOMFVF (D3DFVF_XYZRHW | D3DFVF_DIFFUSE) in directx 10 I believe the equivalent is the input vertex description D3D10_INPUT_ELEMENT_DESC layout[] = { {"POSITION",0,DXGI_FORMAT_R32G32B32_FLOAT, 0 , 0, D3D10_INPUT_PER_VERTEX_DATA, 0}, {"COLOR",0,DXGI_FORMAT_R32G32B32A32_FLOAT, 0 , 12, D3D10_INPUT_PER_VERTEX_DATA, 0} }; I notice in directx 10. it is more descriptive. besides this, what are some of the drastic changes made. and is the hlsl syntax the same for both.

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  • Can you dynamically resize a java.util.concurrent.ThreadPoolExecutor while it still has tasks waitin

    - by Edward Shtern
    I'm working with a java.util.concurrent.ThreadPoolExecutor to process a number of items in parallel. Although the threading itself works fine, at times we've run into other resource constraints due to actions happening in the threads, which made us want to dial down the number of Threads in the pool. I'd like to know if there's a way to dial down the number of the threads while the threads area actually working. I know that you can call setMaximumPoolSize() and/or setCorePoolSize(), but these only resize the pool once threads become idle, but they don't become idle until there are no tasks waiting in the queue.

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  • Core dump utility for .NET

    - by Dave
    In my past life as a COBOL mainframe developer I made extensive use of a tool called Abendaid which, in the event of an exception, would give me a complete memory dump including a formatted list of every variable in memory as well as a complete stack trace of the program with the offending statement highlighted. This made pinpointing the cause of an error much simpler and saved a lot of step-through debugging and/or trace statements. Now I've made the transition to C# and .NET web development I find that the information provided by ASP.NET only tells half the story, giving me a stack trace, but not any of the variable or class information. This makes debugging more difficult as you then have to run the process again with the debugger to try and reproduce the error, not easy with intermittent errors or with assemblies that run under the likes of SQL Server or CRM. I've looked around quite a lot for something that does this but I can't find anything obvious. Does anyone have any idea if there is one, or if not, what I'd need to start with in order to write one?

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  • Interview - Program on Computer

    - by Gilad Naor
    Spent some time searching, couldn't find exactly what I'm after. We like giving hands-on programming exercises as part of the interview process. The interviewee gets a laptop, with the editor and compiler of his choice. He or she then get a programming exercise and has about an hour to code it. Depending on the nature of the question, internet access is either allowed or forbidden. I'm looking for good general questions for a junior developer. I don't care what language they choose to program in. C++ is as good as Python or Scheme, as long as (s)he can program in it (this rules out "can you write a correct copy-constructor" style questions). I just want to see how they code, if their code is self-documenting, if they write tests, check edge-cases, etc. What kind of questions would you ask?

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  • Linux issues on setting a timer function

    - by laura
    I am creating a process with 2 children, 1 of the children is responsible to read questions (line by line from a file), output every question and reading the answer, and the other one is responsable to measure the time elapsed and notify the user at each past 1 minute about the remaining time. My problem is that i couldn't find any useful example of how i can make this set time function to work. Here is what i have tried so far. The problem is that it outputs the same elapsed time every time and never gets out from the loop. #include<time.h> #define T 600000 int main(){ clock_t start, end; double elapsed; start = clock(); end = start + T; while(clock() < end){ elapsed = (double) (end - clock()) / CLOCKS_PER_SEC; printf("you have %f seconds left\n", elapsed); sleep(60); } return 0; }

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  • Action works, but test doesn't (Shoulda)

    - by trobrock
    I am trying to test my update action in Rails with this: context "on PUT to :update" do setup do @countdown = Factory(:countdown) @new_countdown = Factory.stub(:countdown) put :update, :id => @countdown.id, :name => @new_countdown.name, :end => @new_countdown.end end should_respond_with :redirect should_redirect_to("the countdowns view") { countdown_url(assigns(:countdown)) } should_assign_to :countdown should_set_the_flash_to /updated/i should "save :countdown with new attributes" do @countdown = Countdown.find(@countdown.id) assert_equal @new_countdown.name, @countdown.name assert_equal 0, (@new_countdown.end - @countdown.end).to_i end end When I actually go through the updating process using the scaffold that was built it updates the record fine, but the tests give me this error: 1) Failure: test: on PUT to :update should save :countdown with new attributes. (CountdownsControllerTest) [/test/functional/countdowns_controller_test.rb:86:in `__bind_1276353837_121269' /Library/Ruby/Gems/1.8/gems/thoughtbot-shoulda-2.10.2/lib/shoulda/context.rb:351:in `call' /Library/Ruby/Gems/1.8/gems/thoughtbot-shoulda-2.10.2/lib/shoulda/context.rb:351:in `test: on PUT to :update should save :countdown with new attributes. ']: <"Countdown 8"> expected but was <"Countdown 7">.

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  • Python threads all executing on a single core

    - by Rob Lourens
    I have a Python program that spawns many threads, runs 4 at a time, and each performs an expensive operation. Pseudocode: for object in list: t = Thread(target=process, args=(object)) # if fewer than 4 threads are currently running, t.start(). Otherwise, add t to queue But when the program is run, Activity Monitor in OS X shows that 1 of the 4 logical cores is at 100% and the others are at nearly 0. Obviously I can't force the OS to do anything but I've never had to pay attention to performance in multi-threaded code like this before so I was wondering if I'm just missing or misunderstanding something. Thanks.

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  • Use of (non) qualified names

    - by AProgrammer
    If I want to use the name baz defined in package foo|bar|quz, I've several choices: provide fbq as a short name for foo|bar|quz and use fbq|baz use foo|bar|quz|baz import baz from foo|bar|quz|baz and then use baz (or an alias given in the import process) import all public symbols from foo|bar|quz|baz and then use baz For the languages I know, my perception is that the best practice is to use the first two ways (I'll use one or the other depending on the specific package full name and the number of symbols I need from it). I'd use the third only in a language which doesn't provide the first and hunt for supporting tools to write the import statements. And in my opinion the fourth should be reserved to package designed with than import in mind, for instance if all exported symbols start with a prefix or contains the name of the package. My questions: what is in your opinion the best practice for your favorite languages? what would you suggest in a new language? what would you suggest in an old language adding such a feature?

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  • Cannot insert a breakpoint in shared Library

    - by ronan
    Friends While debugging an application of of the function is defined in a shared library which is written by another vendor . and I get an error like warning: Cannot insert breakpoint 0: in /opt/trims/uat/lib/libTIPS_Oleca.sl warning: This is because your shared libraries are not mapped private. To attach to a process and debug its shared libraries you must prepare the program with "/opt/langtools/bin/pxdb -s on a.out or "chatr +dbg enable a.out ".** warning: Add this to your Makefile for debug builds warning: so that each rebuilt debuggable a.out would warning: have this feature turned on. Temporarily disabling shared library breakpoints:0 Now the problem is I cannot modify the shared library . How do I resolve this error ? Many Thanks

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  • Xap file contents changes if built in Visual Studio or build server

    - by arch
    I'm using MEF with my Silverlight 4 app to dynamically load xap files. To optimize this process, I've removed various assemblies from my xaps since I know they've already been loaded by the base xap. This reduces the size of my dynamically loaded xaps. I accomplished this by setting the "Copy Local" flag for each assembly reference to "false". This all seems to work fine when I build in Visual Studio 2010 - my xaps are much smaller. However, when the same projects are built by the build server, all the excluded references are once again in the xap file hence tripling the size of the xap. I've read several blogs/articles regarding similar experiences but no resolution. Very frustrating - any help is appreciated.

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  • How to generate one large dependency map for the whole project that builds with makefiles?

    - by Stan
    I have a gigantic project that is built using makefiles. Running make at the root of the project takes over 20 minutes when no files have changed (i.e. just traversing the project and checking for updated files). I'd like to create a dependency map that will tell me which directories I need to run 'make' in based on the file(s) changed. I already have a list of updated files that I can get from my version control system, and I'd like to skip the 20 minutes of traversing and get straight to the locations that do need to be recompiled. The project has a mix of several languages and custom tools, so this would ideally be language-independent (i.e. it would only process all makefiles to generate dependencies). I'll settle for a C/C++-specific solution, too, as the majority of the project is in C++. The project is built on Linux.

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  • SOAP - Why do I need to query for the values for an update?

    - by Phill Pafford
    I'm taking over a project and wanted to understand if this is common practice using SOAP. The process that is currently in place I have to query all the values before I do an update cause I need to pass back all the values that are not being updated. Does this sound right? Example Values: fname=phill lname=pafford address=123 main phone:222-555-1212 So if I just wanted to update the phone number I need to query for the record, get all the values and submit these values for an update. Example Update Values: fname=phill lname=pafford address=123 main phone:111-555-1212 I just want to know if this is common practice or should I change the functionality of this?

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