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  • Get the lua command when a c function is called

    - by gamernb
    Supposed I register many different function names in Lua to the same function in C. Now, everytime my C function is called, is there a way to determine which function name was invoked? for example: int runCommand(lua_State *lua) { const char *name = // getFunctionName(lua) ? how would I do this part for(int i = 0; i < functions.size; i++) if(functions[i].name == name) functions[i].Call() } int main() { ... lua_register(lua, "delay", runCommand); lua_register(lua, "execute", runCommand); lua_register(lua, "loadPlugin", runCommand); lua_register(lua, "loadModule", runCommand); lua_register(lua, "delay", runCommand); } So, how do I get the name of what ever function called it?

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  • dangling pointer, reason for value change after free()?

    - by Aman Jain
    In the following code segment, after free(x), why does y becomes 0? As per my understanding, the memory in the heap that was being pointed to by x, and is still being pointed by y, hasn't been allocated to someone else, so how can it change to 0? And moreover, I don't think it is free(x) that changed it to 0. Any comments? #include <stdio.h> int main ( int argc, char *argv[] ) { int *y = NULL; int *x = NULL; x = malloc(4); *x = 5; y = x; printf("[%d]\n", *y); //prints 5 free(x); printf("[%d]\n", *y); //why doesn't print 5?, prints 0 instead return 0; }

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  • Query next/previous record

    - by Rob
    I'm trying to find a better way to get the next or previous record from a table. Let's say I have a blog or news table: CREATE TABLE news ( news_id INT UNSIGNED NOT NULL PRIMARY KEY AUTO_INCREMENT, news_datestamp DATETIME NOT NULL, news_author VARCHAR(100) NOT NULL, news_title VARCHAR(100) NOT NULL, news_text MEDIUMTEXT NOT NULL ); Now on the frontend I want navigation buttons for the next or previous records, if i'm sorting by news_id, I can do something rather simple like: SELECT MIN(news_id) AS next_news_id FROM news WHERE news_id > '$old_news_id' LIMIT 1 SELECT MAX(news_id) AS prev_news_id FROM news WHERE news_id < '$old_news_id' LIMIT 1 But the news can be sorted by any field, and I don't necessarily know which field is sorted on, so this won't work if the user sorts on news_author for example. I've resorted to the rather ugly and inefficient method of sorting the entire table and looping through all records until I find the record I need. $res = mysql_query("SELECT news_id FROM news ORDER BY `$sort_column` $sort_way"); $found = $prev = $next = 0; while(list($id) = mysql_fetch_row($res)) { if($found) { $next = $id; break; } if($id == $old_news_id) { $found = true; continue; } $prev = $id; } There's got to be a better way.

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  • Bitwise OR of constants

    - by ryyst
    While reading some documentation here, I came across this: unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit; NSDateComponents *comps = [gregorian components:unitFlags fromDate:date]; I have no idea how this works. I read up on the bitwise operators in C, but I do not understand how you can fit three (or more!) constants inside one int and later being able to somehow extract them back from the int? Digging further down the documentation, I also found this, which is probably related: typedef enum { kCFCalendarUnitEra = (1 << 1), kCFCalendarUnitYear = (1 << 2), kCFCalendarUnitMonth = (1 << 3), kCFCalendarUnitDay = (1 << 4), kCFCalendarUnitHour = (1 << 5), kCFCalendarUnitMinute = (1 << 6), kCFCalendarUnitSecond = (1 << 7), kCFCalendarUnitWeek = (1 << 8), kCFCalendarUnitWeekday = (1 << 9), kCFCalendarUnitWeekdayOrdinal = (1 << 10), } CFCalendarUnit; How do the (1 << 3) statements / variables work? I'm sorry if this is trivial, but could someone please enlighten me by either explaining or maybe posting a link to a good explanation? Thanks! -- ry

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  • OpenCL - incremental summation during compute

    - by user1721997
    I'm absolutelly novice in OpenCL programming. For my app. (molecular simulaton) I wrote a kernel for calculate intermolecular potential of lennard-jones liquid. In this kernel I need to compute cumulative value of the potential of all particles with one: __kernel void Molsim(__global const float* inmatrix, __global float* fi, const int c, const float r1, const float r2, const float r3, const float rc, const float epsilon, const float sigma, const float h1, const float h23) { float fi0; float fi1; float d; unsigned int i = get_global_id(0); //number of particles (typically 2000) if(c!=i) { // potential before particle movement d=sqrt(pow((0.5*h1-fabs(0.5*h1-fabs(inmatrix[c*3]-inmatrix[i*3]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(inmatrix[c*3+1]-inmatrix[i*3+1]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(inmatrix[c*3+2]-inmatrix[i*3+2]))),2.0)); if(d<rc) { fi0=4.0*epsilon*(pow(sigma/d,12.0)-pow(sigma/d,6.0)); } else { fi0=0; } // potential after particle movement d=sqrt(pow((0.5*h1-fabs(0.5*h1-fabs(r1-inmatrix[i*3]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(r2-inmatrix[i*3+1]))),2.0)+pow((0.5*h23-fabs(0.5*h23-fabs(r3-inmatrix[i*3+2]))),2.0)); if(d<rc) { fi1=4.0*epsilon*(pow(sigma/d,12.0)-pow(sigma/d,6.0)); } else { fi1=0; } // cumulative difference of potentials fi[0]+=fi1-fi0; } } My problem is in the line: fi[0]+=fi1-fi0;. In the one-element vector fi[0] are wrong results. I read something about sum reduction, but I do not know how to do it during the calculation. Exist any simple solution of my problem?

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  • [C++] instantiating bitset using hex character.

    - by bndz
    Hey, I'm trying to figure out how to instantiate a 4 bit bitset based on a hex character. For instance, If I have a character with value 'F', I want to create a bitset of size 4 initialized to 1111 or if it is A, i want to initialize it to 1010. I could use a bunch of if statements like so: fn(char c) { bitset<4 temp; if(c == 'F') temp.set(); //... if(c == '9') { temp.set(1); temp.set(3); } //... } This isn't efficient, is there a way of easily converting the string to a decimal integer and constructing the bitset using the last 4 bits of the int? Thanks for any help.

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  • Visual Studio 2005 - VC++ compiler C1001 on Windows 7

    - by Fritz H
    When I try to build a simple "Hello World" C++ app on Windows 7 Beta, using Visual Studio 2005 (VC++2005) I get a rather generic error C1001 error (Internal compiler error) The compiler seems to just crash, and Windows pops up its (un)helpful This program has stopped working dialog. The file it complains about is mcp1.cpp. Has anyone come across this before? Cheers, Fritz EDIT: The code is: #include <iostream> int main(int argc, char** argv) { std::cout << "Hello!"; return 0; } EDIT 2: I have installed SP1 as well as SP1 for Vista. VS popped up a warning saying it needs SP1 for Vista, but installing it makes no difference. No ideas about what I can possibly do to fix this?

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  • How to create a generic C free function .

    - by nomemory
    I have some C structures related to a 'list' data structure. They look like this. struct nmlist_element_s { void *data; struct nmlist_element_s *next; }; typedef struct nmlist_element_s nmlist_element; struct nmlist_s { void (*destructor)(void *data); int (*cmp)(const void *e1, const void *e2); unsigned int size; nmlist_element *head; nmlist_element *tail; }; typedef struct nmlist_s nmlist; This way I can have different data types being hold in "nmlist_element-data" . The "constructor" (in terms of OOP) has the following signature: nmlist *nmlist_alloc(void (*destructor)(void *data)); Where "destructor" is specific function that de-allocated "data" (being hold by the nmlist_element). If I want to have a list containing integers as data, my "destructor" would like this: void int_destructor(void *data) { free((int*)data); } Still i find it rather "unfriendly" for me to write a destructor functions for every simple primitive data type. So is there a trick to write something like this ? (for primitives): void "x"_destructor(void *data, "x") { free(("x" *)data); } PS: I am not a macro fan myself, and in my short experience regarding C, i don't use them, unless necessary.

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  • remote function with pthread

    - by user311130
    Hi all, I wrote some code in c, using pthread (I configured the linker and compiler in eclipse IDE first). #include <pthread.h> #include "starter.h" #include "UI.h" Page* MM; Page* Disk; PCB* all_pcb_array; void* display_prompt(void *id){ printf("Hello111\n"); return NULL; } int main(int argc, char** argv) { printf("Hello\n"); pthread_t *thread = (pthread_t*) malloc (sizeof(pthread_t)); pthread_create(thread, NULL, display_prompt, NULL); printf("Hello\n"); return 1; } that works fine. However, when I move display_prompt to UI.h no "Hello111 " output is printed. anyone know how to solve that? Elad

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  • Puzzle: Overload a C++ function according to the return value

    - by Motti
    We all know that you can overload a function according to the parameters: int mul(int i, int j) { return i*j; } std::string mul(char c, int n) { return std::string(n, c); } Can you overload a function according to the return value? Define a function that returns different things according to how the return value is used: int n = mul(6, 3); // n = 18 std::string s = mul(6, 3); // s = "666" // Note that both invocations take the exact same parameters (same types) You can assume the first parameter is between 0-9, no need to verify the input or have any error handling.

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  • How to convert a C++ program that uses CUDA into MEX

    - by Harold Wellington Graves
    For work, I am converting the Image Denoising program that comes with the CUDA SDK into a MATLAB program. As far as I know, I have made all the necessary changes required by MATLAB, but when I try to call mex on it, MATLAB returns a bunch of linkage errors that I have no idea how to fix. If anyone has any suggestions on what I might be doing wrong, I would greatly appreciate it. The command I am giving MATLAB is: mex imageDenoisingGL.cpp -I..\..\common\inc -IC:\CUDA\include -L..\..\common\lib -lglut32 And the output from MATLAB is a bunch of these: imageDenoisingGL.obj : error LNK2019: unresolved external symbol __imp__cutCheckCmdLineFlag@12 referenced in function "void __cdecl __cutilExit(int,char * *)" (?__cutilExit@@YAXHPAPAD@Z) I am running: Windows XP x32 Visual Studio 2005 MATLAB 2007a

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  • Escape doube and single backslashes in a string in Ruby

    - by Nick Gorbikoff
    Hello. I'm trying to access a network path in my ruby script on a windows platform in a format like this. \\servername\some windows share\folder 1\folder2\ Now If I try to use this as a path, it won't work. Single backslashes are not properly escaped for this script. path = "\\servername\some windows share\folder 1\folder2\" d = Dir.new(path) I tried everything I could think of to properly escape slashes in the path. However I can't escape that single backslash - because of it's special meaning. I tried single quotes, double quotes, escaping backslash itself, using alternate quotes such as %Q{} or %q{}, using ascii to char conversion. Nothing works in a sense that I'm not doing it right. :-) Right now the temp solution is to Map a network drive N:\ pointing to that path and access it that way, but that not a solution. Does anyone have any idea how to properly escape single backslashes? Thank you

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  • Is Boost.Tuple compatible with C++0x variadic templates ?

    - by Thomas Petit
    Hi, I was playing around with variadic templates (gcc 4.5) and hit this problem : template <typename... Args> boost::tuple<Args...> my_make_tuple(Args... args) { return boost::tuple<Args...>(args...); } int main (void) { boost::tuple<int, char> t = my_make_tuple(8, 'c'); } GCC error message : sorry, unimplemented: cannot expand 'Arg ...' into a fixed-length argument list In function 'int my_make_tuple(Arg ...)' If I replace every occurrence of boost::tuple by std::tuple, it compiles fine. Is there a problem in boost tuple implementation ? Or is this a gcc bug ? I must stick with Boost.Tuple for now. Do you know any workaround ? Thanks.

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  • PHP Escaping from HTML, faster, cleanner?!

    - by rno
    I've read about it from the php website (http://us3.php.net/manual/en/language.basic-syntax.phpmode.php) Using: echo "<html tag>" is slower and also annoying because you got to escape char like " with \" But what's about using $output = <<< EOF <html code> EOF; Then later on in the code I can use $output .= <<< EOF <some more html code> EOF; then when I want to print it: echo "$output"; I think it's a great idea, but really wonder what you PHP guru think about it. Cheers, rno

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  • Infinite gtk warnings when I right click on the icon --CLOSED

    - 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? UPDATE This problem also exists with gtk-demo , is it a gtk bug? Can someone verify that? Platform: windows XP UPDATE AGAIN This is indeed a gtk bug,which is un-fixable.

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  • Selecting an area from displayed image using CImg library

    - by sravan
    hi all, i use CImg for my image processing work. I had written a small piece of code which is follows: #include "../CImg.h" #include <iostream> using namespace std; using namespace cimg_library; int main(int argc,char**argv) { CImg<int> img(argv[1]); CImgDisplay disp; disp.assign(img); while(!disp.is_closed) disp.wait(); return 0; } Now i want to select an area from the displayed image. Can some one tell me how to select an area from displayed image and store the selected pixels, and display the selected region in different display window. If some one can provide code, it will be of great help to me. Thank you all

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  • Does malloc() allocate a contiguous block of memory?

    - by user66854
    I have a piece of code written by a very old school programmer :-) . it goes something like this typedef struct ts_request { ts_request_buffer_header_def header; char package[1]; } ts_request_def; ts_request_buffer_def* request_buffer = malloc(sizeof(ts_request_def) + (2 * 1024 * 1024)); the programmer basically is working on a buffer overflow concept. I know the code looks dodgy. so my questions are: Does malloc always allocate contiguous block of memory ?. because in this code if the blocks are not contiguous , the code will fail big time Doing free(request_buffer) , will it free all the bytes allocated by malloc i.e sizeof(ts_request_def) + (2 * 1024 * 1024), or only the bytes of the size of the structure sizeof(ts_request_def) Do you see any evident problems with this approach , i need to discuss this with my boss and would like to point out any loopholes with this approach

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  • Error in IE8 Browser -> Message: Object doesn't support this property or method

    - by tibin mathew
    Hi All, In my joomla project(http://crystalwrightlive.com) home page there is one sliding banner section, but this banner not working in IE browser (working fine in FF browser) and showing following error: Webpage error details User Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 5.1; Trident/4.0; GTB6; InfoPath.2) Timestamp: Sat, 8 May 2010 06:42:15 UTC Message: Object doesn't support this property or method Line: 1 Char: 1 Code: 0 URI: http://crystalwrightlive.com/index.php In index page included a jquery file: http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js when i removed this JS file, no error but this JQuery file needed for this sliding banner. How can i fix this issue, Please anyone help me!!!!

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  • Division by zero: Undefined Behavior or Implementation Defined in C and/or C++ ?

    - by SiegeX
    Regarding division by zero, the standards say: C99 6.5.5p5 - The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined. C++03 5.6.4 - The binary / operator yields the quotient, and the binary % operator yields the remainder from the division of the first expression by the second. If the second operand of / or % is zero the behavior is undefined. If we were to take the above paragraphs at face value, the answer is clearly Undefined Behavior for both languages. However, if we look further down in the C99 standard we see the following paragraph which appears to be contradictory(1): C99 7.12p4 - The macro INFINITY expands to a constant expression of type float representing positive or unsigned infinity, if available; Do the standards have some sort of golden rule where Undefined Behavior cannot be superseded by a (potentially) contradictory statement? Barring that, I don't think it's unreasonable to conclude that if your implementation defines the INFINITY macro, division by zero is defined to be such. However, if your implementation does not define such a macro, the behavior is Undefined. I'm curious what the consensus on this matter for each of the two languages. Would the answer change if we are talking about integer division int i = 1 / 0 versus floating point division float i = 1.0 / 0.0 ? Note (1) The C++03 standard talks about the library which includes the INFINITY macro.

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  • lua string printing

    - by anon
    In C, I have format strings, something like: char *msg = "wlll you marry me" fprintf(stderr, "%s, %s?", name, msg); Now, can I do something similar in lua with format strings? I.e. I want something functionally equivalent to: name .. ", " .. msg .. "?" but not so ugly, in lua. Okay, so I can do string.format("%s, %s?", name, msg), but can I go even a step further, something like perl style, where I can go: "%name, %msg?" Thanks!

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  • C 64-bit Pointer Alignment

    - by DuneBug
    Are pointers on a 64-bit system still 4 byte aligned (similar to a double on a 32 bit system)? Or are they note 8 byte aligned? For example, on a 64-bit system how big is the following data structure: struct a { void* ptr; char myChar; } Would the pointer by 8 byte aligned, causing 7 bytes of padding for the character (total = 8 + 8 = 16)? Or would the pointer be 4 byte aligned (4 bytes + 4 bytes) causing 3 bytes of padding (total = 4 + 4 + 4 = 12)? Thanks, Ryan

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  • Using WINAPI ReadConsole

    - by Jim Fell
    I am trying to use the WINAPI ReadConsole() to wait for any keypress at the end of my Win32 console application. CONSOLE_READCONSOLE_CONTROL tControl; char pStr[65536]; DWORD dwBufLen = 1; DWORD dwCtl; tControl_c.nLength = sizeof( CONSOLE_READCONSOLE_CONTROL ); tControl_c.nInitialChars = 0; tControl_c.dwControlKeyState = 0; tControl_c.dwCtrlWakeupMask = NULL; pBuf[0] = 0x00; do { ReadConsole( hConsole_c, pStr, (*pBufLen) * sizeof(TCHAR), pBufLen, &tControl ); } while ( pStr[0] == 0x00 ); The code executes without throwing an exception. However, when the ReadConsole() function executes the error code ERROR_INVALID_HANDLE (0x06) is flagged. I have verified hConsole_c to be a valid handle. Does anyone have any insight as to what I am doing wrongly? I am using Visual C++ 2008 Express Edition. Thanks.

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  • Why does this give a segmentation fault?

    - by nightcracker
    I'm stunned, why does this code give me a segmentation fault? #include <stdio.h> #define LIMIT 1500000 typedef struct { int p; int a; int b; } triplet; int main(int argc, char **argv) { int i; triplet triplets[LIMIT]; for (i = 0; i < 5; i++) { triplets[i].p = 9; // remove this line and everything works fine } printf("%d\n", triplets[15].p); return 0; } EDIT: After changing LIMIT to 150 I no longer get a segmentation fault, it prints random numbers instead.

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  • IE error with jquery counter plugin

    - by Mankey
    I've implemented a jquery counter script (count up from say 50 to 100 with different increments) that I found from this question: jQuery counter to count up to a target number The scripts works great except for in Internet Explorer 8 (and possibly other IE versions?). Here's an error message from IE with the URL to the creator of the script's demo. Message: 'undefined' is null or not an object Line: 32 Char: 17 Code: 0 URI: http://www.ulmanen.fi/stuff/counter.php I'm just wondering if anyone know how this can be fixed. I'm guessing it has to do with el.html() not finding any data but I can't really figure this out. Thanks for any help ^^ I would reply to that post if I could but I can't seem to find any way of doing so (I'm new to stackoverflow, I think I lack privileges).

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  • Retrieving datatypes from underlying database

    - by H4mm3rHead
    Hi, Im making an application that displays information about an underlying database. The database can be anything, but is typically either Oracle, MSSQL or MySQL. I am trying to extract the datatype but cannot seem to get this right. I have a DbConnection because i dont know whether I need a OleDbConnection or an OdbcConnection. On this connection I make a GetSchema("Columns", "mytablename") query and gets the result back. It seems though that there are some inconsistencies with my datatypes or the query returns different datatypes for the different databases. For instance, in my MSSQL database I query and get an integer back (which seems to be the OleDbType) which I map to a datatype. My varchars is now of type char - no length - and this confuses me a bit. I guess my main question is something like: Is there any way of making a uniform way of extracting datatypes across providers and having an "accurate" representation of the datatype?

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