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• memset on array of structures in C++

  - by garry

  I have another memset question. It appears as if the code I am editing may have some issues (or it's not done the same way in different files) A::LRM las[9]; //A and LRM are both structures with BOOLS and INTS memset(&las, 0, sizeof(las)); typedef Sec SecArray[16]; SecArray rad_array; memset(rad_array, 0, sizeof(SecArray)); The second example appears to be correct because rad_array is the same as the first position in the array. Then the sizeof(SecArray)) would make sense. The first one doesn't seem correct to me. All structs are just BOOLs and INTS nothing dynamic in them. My understanding from my other post about memset was that it followed this format. memset("pointer to object", "what to set it to", "size of object") Can anyone tell me what exactly is going on here if I am incorrect with my theory.

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• View is moved 3 pixels

  - by Jakub

  Hello, In my app I move the table view (in order to make the text fields visible when the keyboard appears). The view is looks following: This is the code I use for resizing the view and moving it up: static const NSUInteger navBarHeight = 44; CGRect appFrame = [[UIScreen mainScreen] applicationFrame]; tableView.frame = CGRectMake(0, navBarHeight, appFrame.size.width, appFrame.size.height-navBarHeight-216); //216 for the keyboard NSIndexPath *indPath = [self getIndexPathForTextField:textField]; //get the field the view should scroll to [tableView scrollToRowAtIndexPath:indPath atScrollPosition:UITableViewScrollPositionMiddle animated:YES]; The problem is that when the view is moved up it also moves 3 pixels into right direction (it is hard to see the difference in the screenshot, but it is visible when the animation is on and I measured the difference with PixelStick tool). Here it is how it looks after the move: My analysis shows that scrolling the table does not influence the move to the right. Any ideas what is wrong in the code above that makes the view move to the right?

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• C++ iterators & loop optimization

  - by Quantum7

  I see a lot of c++ code that looks like this: for( const_iterator it = list.begin(), const_iterator ite = list.end(); it != ite; ++it) As opposed to the more concise version: for( const_iterator it = list.begin(); it != list.end(); ++it) Will there be any difference in speed between these two conventions? Naively the first will be slightly faster since list.end() is only called once. But since the iterator is const, it seems like the compiler will pull this test out of the loop, generating equivalent assembly for both.

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• Why do virtual memory addresses for linux binaries start at 0x8048000?

  - by muteW

  Disassembling an ELF binary on a Ubuntu x86 system I couldn't help but notice that the code(.text) section starts from the virtual address 0x8048000 and all lower memory addresses seem to be unused. This seems to be rather wasteful and all Google turns up is either folklore involving STACK_TOP or protection against null-pointer dereferences. The latter case looks like it can be fixed by using a single page instead of leaving a 128MB gap. So my question is this - is there a definitive answer to why the layout has been fixed to these values or is it just an arbitrary choice?

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• Possible to convert list of #defines into strings (C++)

  - by brandonC

  Suppose I have a list of #defines in a header file for an external library. These #defines represent error codes returned from functions. I want to write a conversion function that can take as an input an error code and return as an output a string literal representing the actual #define name. As an example, if I have #define NO_ERROR 0 #define ONE_KIND_OF_ERROR 1 #define ANOTHER_KIND_OF_ERROR 2 I would like a function to be able to called like int errorCode = doSomeLibraryFunction(); if (errorCode) writeToLog(convertToString(errorCode)); And have convertToString() be able to auto-convert that error code without being a giant switch-case looking like const char* convertToString(int errorCode) { switch (errorCode) { case NO_ERROR: return "NO_ERROR"; case ONE_KIND_OF_ERROR: return "ONE_KIND_OF_ERROR"; ... ... ... I have a feeling that if this is possible, it would be possible using templates and metaprogramming, but that would only work the error codes were actually a type and not a bunch of processor macros. Thanks

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• Official definition of CSCI (Computer Software Configuration Item)

  - by Andreas_D

  I'm looking for the most official definition of CSCI / Configuration Item - not just what it is but what we have to deliver / can expect when a contract defines subsystems which shall be developed as configuration items. I spend some time with my famous search tool and found a lot of explanations for CSCI (wikipedia, acronym directories, ...) but I haven't found a standard or a pointer to a standard (like ISO-xxx) yet which tells (1) what it is and (2) what has to be done from a QM/CM point of view. I just ask, because a contractors QM representative stated during an acceptance test, that CI only requires to not forget the CI in the configuration plan and to assign a serial number ... I expected to see some SRS, SDD, ICD, SVD, SIP, ... documents and acceptance test documentation for those subsystems...

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• SQL tables using VARCHAR with UTF8 (with respect to multi byte character length)

  - by Elius

  Like in Oracle VARCHAR( 60 CHAR ) I would like to specify a varchar field with variable length depending on the inserted characters. for example: create table X (text varchar(3)) insert into X (text) VALUES ('äöü') Should be possible (with UTF8 as the default charset of the database). On DB2 I got this Error: DB2 SQL Error: SQLCODE=-302, SQLSTATE=22001 (Character data, right truncation occurred; for example, an update or insert value is a string that is too long for the column, or a datetime value cannot be assigned to a host variable, because it is too small.) I'm looking for solutions for DB2, MsSql, MySql, Hypersonic.

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• The glutKeyboardFunc does not react to key presses immediately

  - by Nibirue

  I have a function glutKeyboardFunc(keyboard), where keyboard has: void keyboard(unsigned char key, int x, int y){ float alpha = 1.0; switch(key){ case 'c': glClearColor(1,0,0,alpha); printf("success"); break; } } This is a summary of the function; it works properly, but only once some other action has occurred. For instance, the printf statement reports success immediately on keystroke 'c', but the background color does not become active until I click somewhere else on the canvas. I want all keystrokes to have an immediate effect.

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• Oracle spatial search within distance

  - by KA_lin

  I have the following table Cities: ID(int),City(char),latitude(float),longitude(float). Now based on a user`s longitude(ex:44.8) and latitude(ex:46.3) I want to search for all the cities near him within 100 miles/KM. I have found some examples but don`t know how to adapt them to my case select * from GEO.Cities a where SDO_WITHIN_DISTANCE([I don`t know], MDSYS.SDO_GEOMETRY(2001, 8307, MDSYS.SDO_POINT_TYPE(44.8,46.3, NULL) ,NULL, NULL), 'distance = 1000') = 'TRUE'; Any help would be appreciated. P.S: If it is possible to have the distance and to be sorted P.P.S: I want to do it in this way due to performance issues, I have done this in this way http://www.scribd.com/doc/2569355/Geo-Distance-Search-with-MySQL but it takes too long...

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• Reading long lines from text file

  - by sonofdelphi

  I am using the following code for reading lines from a text-file. What is the best method for handling the case where the line is greater than the limit SIZE_MAX_LINE? void TextFileReader::read(string inFilename) { ifstream xInFile(inFilename.c_str()); if(!xInFile){ return; } char acLine[SIZE_MAX_LINE + 1]; while(xInFile){ xInFile.getline(acLine, SIZE_MAX_LINE); if(xInFile){ m_sStream.append(acLine); //Appending read line to string } } xInFile.close(); }

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• crc24 from c to python

  - by biiiiiaw

  can someone please translate this code to python? i have tried and tried again, but have not managed it: #define CRC24_INIT 0xB704CEL #define CRC24_POLY 0x1864CFBL typedef long crc24; crc24 crc_octets(unsigned char *octets, size_t len) { crc24 crc = CRC24_INIT; int i; while (len--) { crc ^= (*octets++) << 16; for (i = 0; i < 8; i++) { crc <<= 1; if (crc & 0x1000000) crc ^= CRC24_POLY; } } return crc & 0xFFFFFFL; } i have the rotate left function (ROL24(value,bits_to_rotate_by)), which i know works since i got it from a source code of a reputable programmer, but i dont get the * and ++ on octet. i only sort of understand how ++ works in c++, and i dont know what * is at all

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• How to call a function from a shared library?

  - by Frank

  What is the easiest and safest way to call a function from a shared library / dll? I am mostly interested in doing this on linux, but it would be better if there were a platform-independent way. Could someone provide example code to show how to make the following work, where the user has compiled his own version of foo into a shared library? // function prototype, implementation loaded at runtime: std::string foo(const std::string); int main(int argc, char** argv) { LoadLibrary(argv[1]); // loads library implementing foo std::cout << "Result: " << foo("test"); return 0; } BTW, I know how to compile the shared lib (foo.so), I just need to know an easy way to load it at runtime.

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• Expected symbol problems with this function declaration

  - by Derek

  I am just getting back into the C programming realm and I am having an issue that I think is linker related. I am using cmake for the first time as well, so that could be adding to my frustration. I have included a third party header file that contains a typedef that my code is trying to use, and it has this line: typedef struct a a_t so my code has a_t *var; //later..... var->member;// this line throws the error which throws the error: dereferencing pointer to incomplete type So am I just missing another include file, or is this a linker issue? I am building this code in QtCreator and using cmake. I can dive on a_t to see that typedef declaration in the included header, but I can't seem to dive on "struct a" itself to see where it's coming from. Thanks

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• How to get notified of modification in the memory in Linux

  - by Song Yuan

  In a userspace program in Linux, I get a piece of memory via allocation from the heap, then the pointer is distributed to a lot of other components running in other threads to use. I would like to get notified when the said piece of memory is modified. I can of course develop a custom userspace solution for other components to use when they try to modify the memory. The problem in my case is that these are legacy components and they can write to memory in many occasions. So I'm wondering whether there is a similar API like inotify (get notified when file is changed) or other approaches in order to get notified when a piece of memory is changed. I considered using mmap and inotify, which obviously won't work if the changes are not flushed. Any suggestions are appreciated :-)

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• Resolve circular typedef dependency?

  - by Nick

  What is the best way to resolve the following circular dependency in typedef-ing these structs? Note the C language tag - I'm looking for a solution in standard gcc C. typedef struct { char* name; int age; int lefthanded; People* friends; } Person; typedef struct { int count; int max; Person* data; } People;

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• How do I change the class of an object to a subclass of its current class in C++?

  - by Jared P

  I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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• boost scoped_lock mutex crashes

  - by JahSumbar

  hello, I have protected a std::queue's access functions, push, pop, size, with boost::mutexes and boost::mutex::scoped_lock in these functions from time to time it crashes in a scoped lock the call stack is this: 0 0x0040f005 boost::detail::win32::interlocked_bit_test_and_set include/boost/thread/win32/thread_primitives.hpp 361 1 0x0040e879 boost::detail::basic_timed_mutex::timed_lock include/boost/thread/win32/basic_timed_mutex.hpp 68 2 0x0040e9d3 boost::detail::basic_timed_mutex::lock include/boost/thread/win32/basic_timed_mutex.hpp 64 3 0x0040b96b boost::unique_lock<boost::mutex>::lock include/boost/thread/locks.hpp 349 4 0x0040b998 unique_lock include/boost/thread/locks.hpp 227 5 0x00403837 MyClass::inboxSize - this is my inboxSize function that uses this code: MyClass::inboxSize () { boost::mutex::scoped_lock scoped_lock(m_inboxMutex); return m_inbox.size(); } and the mutex is declared like this: boost::mutex m_inboxMutex; it crashes at the last pasted line in this function: inline bool interlocked_bit_test_and_set(long* x,long bit) { long const value=1<<bit; long old=*x; and x has this value: 0xababac17 Thanks for the help

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• C++ volatile required when spinning on boost::shared_ptr operator bool()?

  - by JaredC

  I have two threads referencing the same boost::shared_ptr: boost::shared_ptr<Widget> shared; On thread is spinning, waiting for the other thread to reset the boost::shared_ptr: while(shared) boost::thread::yield(); And at some point the other thread will call: shared.reset(); My question is whether or not I need to declare the shared pointer as volatile to prevent the compiler from optimizing the call to shared.operator bool() out of the loop and never detecting the change? I know that if I were simply looping on a variable, waiting for it to reach 0 I would need volatile, but I'm not sure if boost::shared_ptr is implemented in such a way that it is not necessary here.

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• C input loop for shell

  - by AustinM

  So I'm working on creating a very simple C program that just preforms shell commands. This is what I have so far: #include <stdio.h> int main() { char input[30]; fputs("$ ", stdout); fflush(stdout); fgets(input, sizeof input, stdin); system(input); } It works, but only for one command. For example if I compile and type ./cmd I get the $ prompt. If I type ls I get what I'm supposed to get. But then it exits and goes back to the regular system shell. How can I make it so after the user types a command it goes back to the "$" input.

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• How to return a copy of the data in C++

  - by Josh Curren

  I am trying to return a new copy of the data in a C++ Template class. The following code is getting this error: invalid conversion from ‘int*’ to ‘int’. If I remove the new T then I am not returning a copy of the data but a pointer to it. template<class T> T OrderedList<T>::get( int k ) { Node<T>* n = list; for( int i = 0; i < k; i++ ) { n=n->get_link(); } return new T( n->get_data() ); // This line is getting the error ********** }

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• Printing escape character

  - by danutenshu

  When I am given "d""\"/""b", I need to print out the statement character for character. (d, b, a slash, a backslash, and 5 quotes) in C++. The only errors that show now are the lines if(i.at(j)="\\") and else if(i.at(j)="\""). Also, how should the outside double apostrophes be excluded? #include <iostream> #include <cstdlib> using namespace std; int main (int argc, const char* argv[] ) { string i= argv[1]; for (int j=0; j>=sizeof(i)-1; j++) { if(i.at(j)="\\") { cout << "\\"; } else if(i.at(j)="\"") { cout << "\""; } else { cout << i.at(j); } } return 0; }

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• How to get path to current exe file on Linux?

  - by user1519221

  The code below gives current path to exe file on Linux: #include <iostream> std::string getExePath() { char result[ PATH_MAX ]; ssize_t count = readlink( "/proc/self/exe", result, PATH_MAX ); return std::string( result, (count > 0) ? count : 0 ); } int main() { std::cout << getExePath() << std::endl; return 0; } The problem is that when I run it gives me current path to exe and name of the exe, e.g.: /home/.../Test/main.exe I would like to get only /home/.../Test/ I know that I can parse it, but is there any nicer way to do that?

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• How do I get the inner arrays length in a 2d array in C#?

  - by Phukab

  Lets say I create a jagged 2d array like so: public static char[,] phoneLetterMapping = { {'0'}, {'1'}, {'A', 'B', 'C'} }; Now, given the first index of the array, I would like to be able to get the length of the inner array. So, I would like to be able to do something like: phoneLetterMapping[2].length I can do that in Java. But the intellisense menu doesn't return the normal members of an array when I type in the first bracket of the [][] 2d array. So, how do I get the inner array lengths in my 2d array in C#?

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• CSS Position Help (horizontal sidebar showing up when animate content over)

  - by jstacks

  Let me try my best to explain what I'd like to have happen, show you the code I have an hopefully I can get some help. So, I'm trying to do a sliding navigation UI from the left side of the screen (like a lot of mobile apps). The main content slides over, displaying the navigation menu beneath. Right now the browser thinks the screen is getting wider and introduces a horizontal scroll bar. However, I don't want that to happen... How do I get the div to animate off screen but not enlarge the width of the screen (i.e. keep it partially off screen)? Anyway here is my fiddle: http://jsfiddle.net/2vP67/6/ And here is the code within the post: HTML <div id='wrapper'> <div id='navWide'> </div> <div id='containerWide'> </div> <div id='containerTall'> <div id='container'> <div id='nav'> <div id='navNavigate'> Open Menu </div> <div id='navNavigateHide'> Close Menu </div> </div> </div> </div> <div id='sideContainerTall'> <div id='sideContainer'> <div id='sideNav'>Side Navigation </div> </div> </div> </div> CSS #wrapper { width:100%; min-width:1000px; height:100%; min-height:100%; position:relative; top:0; left:0; z-index:0; } #navWide { color: #ffffff; background:#222222; width:100%; min-width:1000px; height:45px; position:fixed; top:0; left:0; z-index:100; } #containerWide { width:100%; min-width:1000px; min-height:100%; position:absolute; top:45px; z-index:100; } #containerTall { color: #000000; background:#dadada; width:960px; min-height:100%; margin-left:-480px; position:absolute; top:0; left:50%; z-index:1000; } /***** main container *****/ #container { width:960px; min-height:585px; } #nav { color: #ffffff; background:#222222; width:960px; height:45px; position:fixed; top:0; z-index:10000; } #navNavigate { background:yellow; font-size:10px; color:#888888; width:32px; height:32px; padding:7px 6px 6px 6px; float:left; cursor:pointer; } #navNavigateHide { background:yellow; font-size:10px; color:#888888; width:32px; height:32px; padding:7px 6px 6px 6px; float:left; cursor:pointer; display:none; } #sideContainerTall { background:#888888; width:264px; min-height:100%; margin-left:-480px; position:absolute; top:0; left:50%; z-index:500; } #sideContainer { width:264px; min-height:585px; display:none; } #sideContainerTall { background:#888888; width:264px; min-height:100%; margin-left:-480px; position:absolute; top:0; left:50%; z-index:500; } #sideContainer { width:264px; min-height:585px; display:none; } #sideNav { width:264px; height:648px; float:left; } Javascript $(document).ready(function() { $('div#navNavigate').click(function() { $('div#navNavigate').hide(); $('div#navNavigateHide').show(); $('div#sideContainer').show(); $('div#containerTall').animate({ 'left': '+=264px' }); }); $('div#navNavigateHide').click(function() { $('div#navNavigate').show(); $('div#navNavigateHide').hide(); $('div#containerTall').animate({ 'left': '-=264px' }, function() { $('div#sideContainer').hide(); }); }); });

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• Infinite gtk warnings when I right click on the icon

  - by Runner

  From this tuto: #include <gtk/gtk.h> int main( int argc, char *argv[]) { GtkWidget *window; gtk_init(&argc, &argv); window = gtk_window_new(GTK_WINDOW_TOPLEVEL); gtk_widget_show(window); gtk_main(); return 0; } I run the executable and right click on the icon,then infinite warnings(the same) reported: GLib-WARNING **: g_main_context_check() called recursively from within a source's check() or prepare() member. Anyone knows how to fix this warning?

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