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• How do I safely destroy a dialog window of a wxPython application?

  - by Akira

  I created a wxPython application which shows some messages on a dialog window. The dialog window is needed to be force-destroyed by the application before I click the dialog OK button. I used wx.lib.delayedresult to make the destroy call. My code is: import wx dlg=wx.MessageDialog(somewindow,'somemessage') from wx.lib.delayedresult import startWorker def _c(d): dlg.EndModal(0) dlg.Destroy() def _w(): import time time.sleep(1.0) startWorker(_c,_w) dlg.ShowModal() This can do what I desire to do while I got a error message below: (python:15150): Gtk-CRITICAL **: gtk_widget_destroy: assertion `GTK_IS_WIDGET (widget)' failed How do I "safely" destroy a dialog without clicking the dialog button?

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• It's easy to set a breakpoint when debugging VBA, but how about a "startpoint" or a "skippoint"?

  - by PowerUser

  I'm debugging a subroutine in my VBA code. I want to ignore the first half and just run the second half. So, is there a way to set a 'startpoint'? Also, is there an easy way to ignore a specific line of code other than commenting? If not, I'll just continue commenting out all the code I don't want run. The problem with this, of course, is that I have to remember to uncomment the critical code before I send it on to Production.

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• TB3.0.10: Messages being sent back to me

  - by punkinette64

  Hello, I don't know if this will make any sense to you; but here goes. When I send an email and I get a response, more often than not, in the 'to:' is my email address. However, my email address also ends up in the 'from' column.The 'reply-from' address is nowhere to be found;so I don't have any address with which I can send my reply, as both of them have just my email address. What am I doing wrong here? Is there some set-up in my TOOLOPTIONS set-up incorrectly? The set-up in OPTIONS is pretty difficult to understand and it doesn't offer any 'to' or 'reply-from' choices. This is critical because I just cannot answer my emails because there is no one I can send a reply to. Please, please try to help me. If you have the answer, please email me at: [email protected] Thank you. Blessings. Shiloh

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• TB3.0.10: Messages being sent back to me

  - by punkinette64

  Hello, I don't know if this will make any sense to you; but here goes. When I send an email and I get a response, more often than not, in the 'to:' is my email address. However, my email address also ends up in the 'from' column.The 'reply-from' address is nowhere to be found;so I don't have any address with which I can send my reply, as both of them have just my email address. What am I doing wrong here? Is there some set-up in my TOOLOPTIONS set-up incorrectly? The set-up in OPTIONS is pretty difficult to understand and it doesn't offer any 'to' or 'reply-from' choices. This is critical because I just cannot answer my emails because there is no one I can send a reply to. Please, please try to help me. If you have the answer, please email me at: [email protected] Thank you. Blessings. Shiloh

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• How can i mock or test my deferred execution functionality?

  - by cottsak

  I have what could be seen as a bizarre hybrid of IQueryable<T> and IList<T> collections of domain objects passed up my application stack. I'm trying to maintain as much of the 'late querying' or 'lazy loading' as possible. I do this in two ways: By using a LinqToSql data layer and passing IQueryable<T>s through by repositories and to my app layer. Then after my app layer passing IList<T>s but where certain elements in the object/aggregate graph are 'chained' with delegates so as to defer their loading. Sometimes even the delegate contents rely on IQueryable<T> sources and the DataContext are injected. This works for me so far. What is blindingly difficult is proving that this design actually works. Ie. If i defeat the 'lazy' part somewhere and my execution happens early then the whole thing is a waste of time. I'd like to be able to TDD this somehow. I don't know a lot about delegates or thread safety as it applies to delegates acting on the same source. I'd like to be able to mock the DataContext and somehow trace both methods of deferring (IQueryable<T>'s SQL and the delegates) the loading so that i can have tests that prove that both functions are working at different levels/layers of the app/stack. As it's crucial that the deferring works for the design to be of any value, i'd like to see tests fail when i break the design at a given level (separate from the live implementation). Is this possible?

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• what are the recent dataStructure and algorithms that one should know?

  - by Shamik

  Recently I came across the SkipList data structure. It really helped me to solve one otherwise critical problem to be solved. I was struggling to solve the same problem with Balanced Binary tree but it became very complex as the tree needs to be always balanced and I wanted to know the existence of not only a particular value but values in certain range. SkipList helped me to solve that problem effectively. I am wondering what else data structures that I need to know? I know - Array, List, Stack, Queue, Linked List, hashtable, tree and its different forms like B-tree, Trie etc. Would like to know if you find some other data structure/concept very interesting to know yet effective enough to be used in a daily development cycle.

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• Preprocessor "macro function" vs. function pointer - best practice?

  - by Dustin

  I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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• How to: Inline assembler in C++ (under Visual Studio 2010)

  - by toxic shock

  I'm writing a performance-critical, number-crunching C++ project where 70% of the time is used by the 200 line core module. I'd like to optimize the core using inline assembly, but I'm completely new to this. I do, however, know some x86 assembly languages including the one used by GCC and NASM. All I know: I have to put the assembler instructions in _asm{} where I want them to be. Problem: I have no clue where to start. What is in which register at the moment my inline assembly comes into play?

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• Performance hit from C++ style casts?

  - by Trevor Boyd Smith

  I am new to C++ style casts and I am worried that using C++ style casts will ruin the performance of my application because I have a real-time-critical deadline in my interrupt-service-routine. I heard that some casts will even throw exceptions! I would like to use the C++ style casts because it would make my code more "robust". However, if there is any performance hit then I will probably not use C++ style casts and will instead spend more time testing the code that uses C-style casts. Has anyone done any rigorous testing/profiling to compare the performance of C++ style casts to C style casts? What were your results? What conclusions did you draw?

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• assignment vs std::swap and merging and keeping duplicates in seperate object

  - by rubenvb

  Say I have two std::set<std::string>s. The first one, old_options, needs to be merged with additional options, contained in new_options. I can't just use std::merge (well, I do, but not only that) because I also check for doubles and warn the user about this accordingly. To this effect, I have void merge_options( set<string> &old_options, const set<string> &new_options ) { // find duplicates and create merged_options, a stringset containing the merged options // handle duplicated the way I want to // ... old_options = merged_options; } Is it better to use std::swap( merged_options, old_options ); or the assignment I have? Is there a better way to filter duplicates and return the merged set than consecutive calls to std::set_intersection and std::set_union to detect dupes and merge the sets? I know it's slower than one traversal and doing both at once, but these sets are small (performance is not critical) and I trust the Standard more than I trust myself.

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• Password security; Is this safe?

  - by Camran

  I asked a question yesterday about password safety... I am new at security... I am using a mysql db, and need to store users passwords there. I have been told in answers that hashing and THEN saving the HASHED value of the password is the correct way of doing this. So basically I want to verify with you guys this is correct now. It is a classifieds website, and for each classified the user puts, he has to enter a password so that he/she can remove the classified using that password later on (when product is sold for example). In a file called "put_ad.php" I use the $_POST method to fetch the pass from a form. Then I hash it and put it into a mysql table. Then whenever the users wants to delete the ad, I check the entered password by hashing it and comparing the hashed value of the entered passw against the hashed value in the mysql db, right? BUT, what if I as an admin want to delete a classified, is there a method to "Unhash" the password easily? sha1 is used currently btw. some code is very much appreciated. Thanks

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• Is there any class in the .NET Framework to represent a holding container for objects?

  - by Charles Prakash Dasari

  I am looking for a class that defines a holding structure for an object. The value for this object could be set at a later time than when this container is created. It is useful to pass such a structure in lambdas or in callback functions etc. Say: class HoldObject<T> { public T Value { get; set; } public bool IsValueSet(); public void WaitUntilHasValue(); } // and then we could use it like so ... HoldObject<byte[]> downloadedBytes = new HoldObject<byte[]>(); DownloadBytes("http://www.stackoverflow.com", sender => downloadedBytes.Value = sender.GetBytes()); It is rather easy to define this structure, but I am trying to see if one is available in FCL. I also want this to be an efficient structure that has all needed features like thread safety, efficient waiting etc. Any help is greatly appreciated.

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• Does it make sense to study COBOL?

  - by Alon

  I have had a talk with a friend of mine about the relative vulnerability of different types of IT workers to unexpected unemployment (e.g. layoffs, company going out of business, obsolete skills etc.) as it seems COBOL developers (or maintainers?) seems very secure in their positions, regardless of the state if the economy or even how good they are. With so much critical COBOL code being around on the one side and the deminishing number of COBOL know-hows on the other , it actually makes sense to recommend someone starting their way in the IT world and looking for a relativity secure job to study and intern in COBOL! what do you think ?

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• Architecture of a secure application that encrypts data in the database.

  - by Przemyslaw Rózycki

  I need to design an application that protects some data in a database against root attack. It means, that even if the aggressor takes control over the machine where data is stored or machine with the application server, he can't read some business critical data from the database. This is a customer's requirement. I'm going to encrypt data with some assymetric algorithm and I need some good ideas, where to store private keys, so that data is secure as well as the application usability was quite comfortable? We can assume, for simplicity, that only one key pair is used.

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• Resources for memory management in embedded application

  - by Elazar Leibovich

  How should I manage memory in my mission critical embedded application? I found some articles with google, but couldn't pinpoint a really useful practical guide. The DO-178b forbids dynamic memory allocations, but how will you manage the memory than? preallocate everything in advance and send a pointer to each function that needs allocation? Allocate it on the stack? Use a global static allocator (but then it's very similar to dynamic allocation)? Answers can be of the form of regular answer, reference to a resource, or reference to good opensource embedded system for example. clarification: The issue here is not whether or not memory management is availible for the embedded system. But what is a good design for an embedded system, to maximize reliability.

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• Can I use memcpy in C++ to copy classes that have no pointers or virtual functions

  - by Shane MacLaughlin

  Say I have a class, something like the following; class MyClass { public: MyClass(); int a,b,c; double x,y,z; }; #define PageSize 1000000 MyClass Array1[PageSize],Array2[PageSize]; If my class has not pointers or virtual methods, is it safe to use the following? memcpy(Array1,Array2,PageSize*sizeof(MyClass)); The reason I ask, is that I'm dealing with very large collections of paged data, as decribed here, where performance is critical, and memcpy offers significant performance advantages over iterative assignment. I suspect it should be ok, as the 'this' pointer is an implicit parameter rather than anything stored, but are there any other hidden nasties I should be aware of?

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• How much trust can I put behind a computer system? How can I measure trust?

  - by danmine

  How much trust can I put in a standard computer running windows? To what certainty can I be sure it will run my code the way I wrote it? How can I be sure that if I declare something like "int j = 5;", j will alway be 5? Is there a way to measure trust in a standard x86 computer system? What kind of protections are there to make sure that j = 5? I'm thinking about critical systems where nothing can be off even by one bit and everything must run exactly the way it was written to run.

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• how to "lock" live site when doing (phing) deployment

  - by Jorre

  On http://www.slideshare.net/eljefe/automated-deployment-with-phing in slide 15 they are talking about "locking the live site" when doing deployment. We are running multiple webshops in a SAAS application where it is possible that users are adding products, buying products and paying for products online, and so on... When deploying we want to do this as clean as possible, so that not payments or orders or other critical data will be lost. We have a deployment scenario set up using phing (amazing tool!) but we are missing one crucial step being the "locking of the live site" while deploying. What is a possible way to lock a live site and bring it back online after deploying?

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• Using stringstream instead of `sscanf` to parse a fixed-format string

  - by John Dibling

  I would like to use the facilities provided by stringstream to extract values from a fixed-format string as a type-safe alternative to sscanf. How can I do this? Consider the following specific use case. I have a std::string in the following fixed format: YYYYMMDDHHMMSSmmm Where: YYYY = 4 digits representing the year MM = 2 digits representing the month ('0' padded to 2 characters) DD = 2 digits representing the day ('0' padded to 2 characters) HH = 2 digits representing the hour ('0' padded to 2 characters) MM = 2 digits representing the minute ('0' padded to 2 characters) SS = 2 digits representing the second ('0' padded to 2 characters) mmm = 3 digits representing the milliseconds ('0' padded to 3 characters) Previously I was doing something along these lines: string s = "20101220110651184"; unsigned year = 0, month = 0, day = 0, hour = 0, minute = 0, second = 0, milli = 0; sscanf(s.c_str(), "%4u%2u%2u%2u%2u%2u%3u", &year, &month, &day, &hour, &minute, &second, &milli ); The width values are magic numbers, and that's ok. I'd like to use streams to extract these values and convert them to unsigneds in the interest of type safety. But when I try this: stringstream ss; ss << "20101220110651184"; ss >> setw(4) >> year; year retains the value 0. It should be 2010. How do I do what I'm trying to do? I can't use Boost or any other 3rd party library, nor can I use C++0x.

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• How to create a GtkImage from a Cairo context?

  - by Zurbo82

  I got a paint function that works using a Cairo context and the end result should be a GtkImage (without intermediate image creation). I tried to use the gdk_cairo_create function but this code: ... GdkPixbuf *pixbuf = gdk_pixbuf_new (GDK_COLORSPACE_RGB, FALSE, 8, 22, 22); GtkWidget *image = gtk_image_new_from_pixbuf (pixbuf); GdkDrawable *drawable = image->window; cairo_t *ctx = gdk_cairo_create (drawable); my_cairo_paint_function (ctx); ... fails with: Gdk-CRITICAL **: IA__gdk_cairo_create: assertion `GDK_IS_DRAWABLE (drawable)' failed Same with a simple: #include <gtk/gtk.h> #include <cairo.h> int main (int argc, char *argv[]) { gtk_init(&argc, &argv); cairo_t *ctx = gdk_cairo_create (gtk_widget_get_window (gtk_image_new_from_file ("foobar.png"))); gtk_main(); return 0; } I don't understand why this fails. Any help is appreciated!

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• server reboot has caused django project to lose directories

  - by wmfox3

  A fully functional Django project as well as a couple in development have all broken following the rebooting of the server. In addition to some pieces of the Django admin returning errors as well as missing .js and .css files, I'm getting errors like this when viewing pages that include images uploaded through the admin. Exception Type: TemplateSyntaxError Exception Value: Caught an exception while rendering: (2, 'No such file or directory') Exception Location: /usr/lib/pymodules/python2.6/django/template/debug.py in render_node, line 81 Python Executable: /usr/bin/python Python Version: 2.6.4 So did the reboot stomp on some part of my configuration/setup or did it fail to restart a critical piece?

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• Torrents: Can I protect my software by sending wrong bytes?

  - by Martijn Courteaux

  Hi, It's a topic that everyone interests. How can I protect my software against stealing, hacking, reverse engineering? I was thinking: Do my best to protect the program for reverse engineering. Then people will crack it and seed it with torrents. Then I download my own cracked software with a torrent with my own torrent-software. My own torrent-software has then to seed incorrect data (bytes). Of course it has to seed critical bytes. So people who want to steal my software download my wrong bytes. Just that bytes that are important to startup, saving and loading data, etc... So if the stealer download from me (and seed it later) can't do anything with it, because it is broken. Is this idea relevant? Maybe, good torrent-clients check hashes from more peers to check if the packages (containing my broken bytes) I want to seed are correct or not? Thanks

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• Good simple C/C++ FTP and SFTP client library recommendation for embedded Linux

  - by Roman Nikitchenko

  Could anyone recommend FTP / SFTP client C/C++ library for Linux-based embedded system? I know about Curl library but I need something as simple as possible just to download files from FTP / SFTP servers. Is there any recommendation to look for? Yes, SFTP support is critical. Actually I can even sacrifice multi-threading because I need only one stream at a time. And I'd like it to be able to work through memory buffers but this should be not a problem. Thank you in advance.

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• "Cannot use fixed local inside lambda expression"

  - by JulianR

  I have an XNA 3.0 project that compiled just fine in VS2008, but that gives compile errors in VS2010 (with XNA 4.0 CTP). The error: Cannot use fixed local 'depthPtr' inside an anonymous method, lambda expression, or query expression depthPtr is a fixed float* into an array, that is used inside a Parallel.For lambda expression from System.Threading. As I said, this compiled and ran just fine on VS2008, but it does not on VS2010, even when targeting .NET 3.5. Has this changed in .NET 4.0, and even so, shouldn't it still compile when I choose .NET 3.5 as the target framework? Searching for the term "Cannot use fixed local" yields exactly one (useless) result, both in Google and Bing. If this has changed, what is the reason for this? I can imagine capturing a fixed pointer-type in a closure could get a bit weird, is that why? So I'm guessing this is bad practice? And before anyone asks: no, the use of pointers is not absolutely critical here. I would still like to know though :)

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• Securing a REST API

  - by Christopher McCann

  I am in the middle of developing a REST API - the first one I ever have. The data being passed through the API is not of such a critical nature that there will be loss of life, economics etc if it was intercepted but at the same time I would like it to be secure. The data being transferred is simply like the data that would be transferred on Twitter or Facebook - not overly confidential but still should be kept private. What is the best way to secure this data? Am I best to use HTTP Basic Auth over SSL or should I be looking into something like OAuth. I have never really used REST much before so bit of a first for me. Thanks

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