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  • Java and C++ on Stack Unwinding issue

    - by sahs-i-muhterem
    As far as I know, in case of an uncaught exception, C++ destroys the local variables immediately, Java releases the references and leaves the rest for the garbage collector. Is this right? What exactly is the difference between Java and C++ on this issue? in other words, which of these two languages is considered better in terms of stack unwinding issue? :)

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  • Help debugging c fifos code - stack smashing detected - open call not functioning - removing pipes

    - by nunos
    I have three bugs/questions regarding the source code pasted below: stack smashing deteced: In order to compile and not have that error I have addedd the gcc compile flag -fno-stack-protector. However, this should be just a temporary solution, since I would like to find where the cause for this is and correct it. However, I haven't been able to do so. Any clues? For some reason, the last open function call doesn't work and the programs just stops there, without an error, even though the fifo already exists. I want to delete the pipes from the filesystem after before terminating the processes. I have added close and unlink statements at the end, but the fifos are not removed. What am I doing wrong? Thanks very much in advance. P.S.: I am pasting here the whole source file for additional clarity. Just ignore the comments, since they are in my own native language. server.c: #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <errno.h> #define MAX_INPUT_LENGTH 100 #define FIFO_NAME_MAX_LEN 20 #define FIFO_DIR "/tmp/" #define FIFO_NAME_CMD_CLI_TO_SRV "lrc_cmd_cli_to_srv" typedef enum { false, true } bool; bool background = false; char* logfile = NULL; void read_from_fifo(int fd, char** var) { int n_bytes; read(fd, &n_bytes, sizeof(int)); *var = (char *) malloc (n_bytes); read(fd, *var, n_bytes); printf("read %d bytes '%s'\n", n_bytes, *var); } void write_to_fifo(int fd, char* data) { int n_bytes = (strlen(data)+1) * sizeof(char); write(fd, &n_bytes, sizeof(int)); //primeiro envia o numero de bytes que a proxima instrucao write ira enviar write(fd, data, n_bytes); printf("writing %d bytes '%s'\n", n_bytes, data); } int main(int argc, char* argv[]) { //CRIA FIFO CMD_CLI_TO_SRV, se ainda nao existir char* fifo_name_cmd_cli_to_srv; fifo_name_cmd_cli_to_srv = (char*) malloc ( (strlen(FIFO_NAME_CMD_CLI_TO_SRV) + strlen(FIFO_DIR) + 1) * sizeof(char) ); strcpy(fifo_name_cmd_cli_to_srv, FIFO_DIR); strcat(fifo_name_cmd_cli_to_srv, FIFO_NAME_CMD_CLI_TO_SRV); int n = mkfifo(fifo_name_cmd_cli_to_srv, 0660); //TODO ver permissoes if (n < 0 && errno != EEXIST) //se houver erro, e nao for por causa de ja haver um com o mesmo nome, termina o programa { fprintf(stderr, "erro ao criar o fifo\n"); fprintf(stderr, "errno: %d\n", errno); exit(4); } //se por acaso já existir, nao cria o fifo e continua o programa normalmente //le informacao enviada pelo cliente, nesta ordem: //1. pid (em formato char*) do processo cliente //2. comando /CONNECT //3. nome de fifo INFO_SRV_TO_CLIXXX //4. nome de fifo MSG_SRV_TO_CLIXXX char* command; char* fifo_name_info_srv_to_cli; char* fifo_name_msg_srv_to_cli; char* client_pid_string; int client_pid; int fd_cmd_cli_to_srv, fd_info_srv_to_cli; fd_cmd_cli_to_srv = open(fifo_name_cmd_cli_to_srv, O_RDONLY); read_from_fifo(fd_cmd_cli_to_srv, &client_pid_string); client_pid = atoi(client_pid_string); read_from_fifo(fd_cmd_cli_to_srv, &command); //recebe commando /CONNECT read_from_fifo(fd_cmd_cli_to_srv, &fifo_name_info_srv_to_cli); //recebe nome de fifo INFO_SRV_TO_CLIXXX read_from_fifo(fd_cmd_cli_to_srv, &fifo_name_msg_srv_to_cli); //recebe nome de fifo MSG_TO_SRV_TO_CLIXXX //CIRA FIFO MSG_CLIXXX_TO_SRV char fifo_name_msg_cli_to_srv[FIFO_NAME_MAX_LEN]; strcpy(fifo_name_msg_cli_to_srv, FIFO_DIR); strcat(fifo_name_msg_cli_to_srv, "lrc_msg_cli"); strcat(fifo_name_msg_cli_to_srv, client_pid_string); strcat(fifo_name_msg_cli_to_srv, "_to_srv"); n = mkfifo(fifo_name_msg_cli_to_srv, 0660); if (n < 0) { fprintf(stderr, "error creating %s\n", fifo_name_msg_cli_to_srv); fprintf(stderr, "errno: %d\n", errno); exit(5); } //envia ao cliente a resposta ao commando /CONNECT fd_info_srv_to_cli = open(fifo_name_info_srv_to_cli, O_WRONLY); write_to_fifo(fd_info_srv_to_cli, fifo_name_msg_cli_to_srv); free(logfile); free(fifo_name_cmd_cli_to_srv); close(fd_cmd_cli_to_srv); unlink(fifo_name_cmd_cli_to_srv); unlink(fifo_name_msg_cli_to_srv); unlink(fifo_name_msg_srv_to_cli); unlink(fifo_name_info_srv_to_cli); printf("fim\n"); return 0; } client.c: #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h> #include <errno.h> #define MAX_INPUT_LENGTH 100 #define PID_BUFFER_LEN 10 #define FIFO_NAME_CMD_CLI_TO_SRV "lrc_cmd_cli_to_srv" #define FIFO_NAME_INFO_SRV_TO_CLI "lrc_info_srv_to_cli" #define FIFO_NAME_MSG_SRV_TO_CLI "lrc_msg_srv_to_cli" #define COMMAND_MAX_LEN 100 #define FIFO_DIR "/tmp/" typedef enum { false, true } bool; char* nickname; char* name; char* email; void write_to_fifo(int fd, char* data) { int n_bytes = (strlen(data)+1) * sizeof(char); write(fd, &n_bytes, sizeof(int)); //primeiro envia o numero de bytes que a proxima instrucao write ira enviar write(fd, data, n_bytes); printf("writing %d bytes '%s'\n", n_bytes, data); } void read_from_fifo(int fd, char** var) { int n_bytes; read(fd, &n_bytes, sizeof(int)); *var = (char *) malloc (n_bytes); printf("read '%s'\n", *var); read(fd, *var, n_bytes); } int main(int argc, char* argv[]) { pid_t pid = getpid(); //CRIA FIFO INFO_SRV_TO_CLIXXX char pid_string[PID_BUFFER_LEN]; sprintf(pid_string, "%d", pid); char* fifo_name_info_srv_to_cli; fifo_name_info_srv_to_cli = (char *) malloc ( (strlen(FIFO_DIR) + strlen(FIFO_NAME_INFO_SRV_TO_CLI) + strlen(pid_string) + 1 ) * sizeof(char) ); strcpy(fifo_name_info_srv_to_cli, FIFO_DIR); strcat(fifo_name_info_srv_to_cli, FIFO_NAME_INFO_SRV_TO_CLI); strcat(fifo_name_info_srv_to_cli, pid_string); int n = mkfifo(fifo_name_info_srv_to_cli, 0660); if (n < 0) { fprintf(stderr, "error creating %s\n", fifo_name_info_srv_to_cli); fprintf(stderr, "errno: %d\n", errno); exit(6); } int fd_cmd_cli_to_srv, fd_info_srv_to_cli; fd_cmd_cli_to_srv = open("/tmp/lrc_cmd_cli_to_srv", O_WRONLY); char command[COMMAND_MAX_LEN]; printf("> "); scanf("%s", command); while (strcmp(command, "/CONNECT")) { printf("O primeiro comando deverá ser \"/CONNECT\"\n"); printf("> "); scanf("%s", command); } //CRIA FIFO MSG_SRV_TO_CLIXXX char* fifo_name_msg_srv_to_cli; fifo_name_msg_srv_to_cli = (char *) malloc ( (strlen(FIFO_DIR) + strlen(FIFO_NAME_MSG_SRV_TO_CLI) + strlen(pid_string) + 1) * sizeof(char) ); strcpy(fifo_name_msg_srv_to_cli, FIFO_DIR); strcat(fifo_name_msg_srv_to_cli, FIFO_NAME_MSG_SRV_TO_CLI); strcat(fifo_name_msg_srv_to_cli, pid_string); n = mkfifo(fifo_name_msg_srv_to_cli, 0660); if (n < 0) { fprintf(stderr, "error creating %s\n", fifo_name_info_srv_to_cli); fprintf(stderr, "errno: %d\n", errno); exit(7); } // ENVIA COMANDO /CONNECT write_to_fifo(fd_cmd_cli_to_srv, pid_string); //envia pid do processo cliente write_to_fifo(fd_cmd_cli_to_srv, command); //envia commando /CONNECT write_to_fifo(fd_cmd_cli_to_srv, fifo_name_info_srv_to_cli); //envia nome de fifo INFO_SRV_TO_CLIXXX write_to_fifo(fd_cmd_cli_to_srv, fifo_name_msg_srv_to_cli); //envia nome de fifo MSG_TO_SRV_TO_CLIXXX // recebe do servidor a resposta ao comanddo /CONNECT printf("msg1\n"); printf("vamos tentar abrir %s\n", fifo_name_info_srv_to_cli); fd_info_srv_to_cli = open(fifo_name_info_srv_to_cli, O_RDONLY); printf("%s aberto", fifo_name_info_srv_to_cli); if (fd_info_srv_to_cli < 0) { fprintf(stderr, "erro ao criar %s\n", fifo_name_info_srv_to_cli); fprintf(stderr, "errno: %d\n", errno); } printf("msg2\n"); char* fifo_name_msg_cli_to_srv; printf("msg3\n"); read_from_fifo(fd_info_srv_to_cli, &fifo_name_msg_cli_to_srv); printf("msg4\n"); free(nickname); free(name); free(email); free(fifo_name_info_srv_to_cli); free(fifo_name_msg_srv_to_cli); unlink(fifo_name_msg_srv_to_cli); unlink(fifo_name_info_srv_to_cli); printf("fim\n"); return 0; } makefile: CC = gcc CFLAGS = -Wall -lpthread -fno-stack-protector all: client server client: client.c $(CC) $(CFLAGS) client.c -o client server: server.c $(CC) $(CFLAGS) server.c -o server clean: rm -f client server *~

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  • free() on stack memory

    - by vidicon
    I'm supporting some c code on Solaris, and I've seen something weird at least I think it is: char new_login[64]; ... strcpy(new_login, (char *)login); ... free(new_login); My understanding is that since the variable is a local array the memory comes from the stack and does not need to be freed, and moreover since no malloc/calloc/realloc was used the behaviour is undefined. This is a real-time system so I think it is a waste of cycles. Am I missing something obvious?

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  • How to implement a graph-structured stack?

    - by Emil
    Ok, so I would like to make a GLR parser generator. I know there exist such programs better than what I will probably make, but I am doing this for fun/learning so that's not important. I have been reading about GLR parsing and I think I have a decent high level understanding of it now. But now it's time to get down to business. The graph-structured stack (GSS) is the key data structure for use in GLR parsers. Conceptually I know how GSS works, but none of the sources I looked at so far explain how to implement GSS. I don't even have an authoritative list of operations to support. Can someone point me to some good sample code/tutorial for GSS? Google didn't help so far. I hope this question is not too vague.

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  • Are stack based arrays possible in C#?

    - by Bob
    Let's say, hypothetically (read: I don't think I actually need this, but I am curious as the idea popped into my head), one wanted an array of memory set aside locally on the stack, not on the heap. For instance, something like this: private void someFunction() { int[20] stackArray; //C style; I know the size and it's set in stone } I'm guessing the answer is no. All I've been able to find is heap based arrays. If someone were to need this, would there be any workarounds? Is there any way to set aside a certain amount of sequential memory in a "value type" way? Or are structs with named parameters the only way (like the way the Matrix struct in XNA has 16 named parameters (M11-M44))?

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  • Stack memory in Android

    - by Matt
    I'm writing an app that has a foreground service, content provider, and a Activity front end that binds to the service and gets back a List of objects using AIDL. The service does work and updates a database. If I leave the activity open for 4-8+ hours, and go to the "Running Services" section under settings on the phone (Nexus One) an unusually large amount of memory being used is shown (~42MB). I figure there is a leak. When I check the heap memory i get Heap size:~18MB, ~2MB allocated, ~16MB free. Analyzing the hprof in Eclipse MAT seems fine, which leads me to theorize that memory is leaking on the stack. Is this even possible? If it is, what can I do to stop or investigate the leak? Is the reported memory usage on the "Running Services" section of android even correct (I assume it is)? Another note: I have been unable to reproduce this issue when the UI is not up (with only the service running)

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  • Stack calling convention between .NET & C on WinCE 6.0

    - by bernard
    Hi there. I'm porting a DLL written in C from WinCE 5.0 to WinCE 6.0 on an ARM target. This DLL is called by a .NET software. On WinCE5.0, everything runs fine. On WinCE6, I have the following problem: on InitInstance() of my DLL, I can call anything without problem (for example MessageBox()) or uses recursivity. Passed that point, the DLL is called by .NET code. And then it fails: even the arguments passed by .NET code seem weird. I can call MessageBox() once, but I can't call a function that calls MessageBox() and then that calls itself: recursivity is broken. It seems that the .NET code uses the stack in a different way than my C code. I'm very unfamillar with the Windows world and the company that gives me the .NET application does not understand yet why there is such a failure. Any pointer/hint/advice welcome! Thanks!

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  • C++ stack memory still valid?

    - by jbu
    Hi all, If I create an object on the stack and push it into a list, then the object loses scope (outside of the for loop in the example below) will the object still exist in the list? If the list still holds the object, is that data now invalid/possibly corrupt? Please let me know, and please explain the reasoning.. Thanks, jbu class SomeObject{ public: AnotherObject x; } //And then... void someMethod() { std::list<SomeObject> my_list; for(int i = 0; i < SOME_NUMBER; i++) { SomeObject tmp; my_list.push_back(tmp); //after the for loop iteration, tmp loses scope } my_list.front(); //at this point will my_list be full of valid SomeObjects or will the SomeObjects no longer be valid, even if they still point to dirty data }

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  • What is the effect of running an application with "Unlimited Stack" size

    - by NSA
    Hello All, I have inherited some code that I need to maintain that can be less than stable at times. The previous people are no longer available to query as to why they ran the application in an environment with unlimited stack set, I am curious what the effects of this could be? The application seems to have some unpredictable memory bugs that we cannot find and running the application under valgrind is not an option because it slows the application down so much that we cannot actually run it. So any thoughts on what the effects of this might be are appreciated. Thank you.

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  • Adding "this" to the parents stack for "each" in jQuery

    - by Matrym
    This question is a bit of a two-parter. First, the title question. Here's what I've got: // Report all of the parents $(this).parents().each(function(i){ // Collect the parts in a var var $crumb = ''; // Get the tag name of the parent $crumb += "<span class='tagName'>"+this.tagName+"</span>"; // And finally, report it $breadcrumbs.prepend($crumb); }); Unfortunately, this doesn't include the actual element itself, only the parents. Is there any way of saying something like "this and parents"? Now, the second question. If I were unable to add to the stack, how would I separate the guts of that function into another function, while retaining the "this" ability of it? Would it be something like: // Function to report the findings function crumble(e){ // Collect the parts in a var var $crumb = ''; // Get the tag name of the parent $crumb += "<span class='tagName'>"+this.tagName+"</span>"; // And finally, report it $breadcrumbs.prepend($crumb); }; $(this).parents().each(crumble()); Thanks in advance for your time!

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  • Stack and Hash joint

    - by Alexandru
    I'm trying to write a data structure which is a combination of Stack and HashSet with fast push/pop/membership (I'm looking for constant time operations). Think of Python's OrderedDict. I tried a few things and I came up with the following code: HashInt and SetInt. I need to add some documentation to the source, but basically I use a hash with linear probing to store indices in a vector of the keys. Since linear probing always puts the last element at the end of a continuous range of already filled cells, pop() can be implemented very easy without a sophisticated remove operation. I have the following problems: the data structure consumes a lot of memory (some improvement is obvious: stackKeys is larger than needed). some operations are slower than if I have used fastutil (eg: pop(), even push() in some scenarios). I tried rewriting the classes using fastutil and trove4j, but the overall speed of my application halved. What performance improvements would you suggest for my code? What open-source library/code do you know that I can try?

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  • segmentation fault on Unix - possible stack corruption

    - by bob
    hello, i'm looking at a core from a process running in Unix. Usually I can work my around and root into the backtrace to try identify a memory issue. In this case, I'm not sure how to proceed. Firstly the backtrace only gives 3 frames where I would expect alot more. For those frames, all the function parameters presented appears to completely invalid. There are not what I would expect. Some pointer parameters have the following associated with them - Cannot access memory at address Would this suggest some kind of complete stack corruption. I ran the process with libumem and all the buffers were reported as being clean. umem_status reported nothing either. so basically I'm stumped. What is the likely causes? What should I look for in code since libumem appears to have reported no errors. Any suggestions on how I can debug furhter? any extra features in mdb I should consider? thank you.

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  • How to debug anomalous C memory/stack problems

    - by EBM
    Hello, Sorry I can't be specific with code, but the problems I am seeing are anomalous. Character string values seem to be getting changed depending on other, unrelated code. For example, the value of the argument that is passed around below will change merely depending on if I comment out one or two of the fprintf() calls! By the last fprintf() the value is typically completely empty (and no, I have checked to make sure I am not modifying the argument directly... all I have to do is comment out a fprintf() or add another fprintf() and the value of the string will change at certain points!): static process_args(char *arg) { /* debug */ fprintf(stderr, "Function arg is %s\n", arg); ...do a bunch of stuff including call another function that uses alloc()... /* debug */ fprintf(stderr, "Function arg is now %s\n", arg); } int main(int argc, char *argv[]) { char *my_arg; ... do a bunch of stuff ... /* just to show you it's nothing to do with the argv array */ my_string = strdup(argv[1]); /* debug */ fprintf(stderr, "Argument 1 is %s\n", my_string); process_args(my_string); } There's more code all around, so I can't ask for someone to debug my program -- what I want to know is HOW can I debug why character strings like this are getting their memory changed or overwritten based on unrelated code. Is my memory limited? My stack too small? How do I tell? What else can I do to track down the issue? My program isn't huge, it's like a thousand lines of code give or take and a couple dynamically linked external libs, but nothing out of the ordinary. HELP! TIA!

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  • Why is my Pre to Postfix code not working?

    - by Anthony Glyadchenko
    For a class assignment, I have to use two stacks in C++ to make an equation to be converted to its left to right equivalent: 2+4*(3+4*8) -- 35*4+2 -- 142 Here is the main code: #include <iostream> #include <cstring> #include "ctStack.h" using namespace std; int main (int argc, char * const argv[]) { string expression = "2+4*2"; ctstack *output = new ctstack(expression.length()); ctstack *stack = new ctstack(expression.length()); bool previousIsANum = false; for(int i = 0; i < expression.length(); i++){ switch (expression[i]){ case '(': previousIsANum = false; stack->cmstackPush(expression[i]); break; case ')': previousIsANum = false; char x; while (x != '('){ stack->cmstackPop(x); output->cmstackPush(x); } break; case '0': case '1': case '2': case '3': case '4': case '5': case '6': case '7': case '8': case '9': cout << "A number" << endl; previousIsANum = true; output->cmstackPush(expression[i]); break; case '+': previousIsANum = false; cout << "+" << endl; break; case '-': previousIsANum = false; cout << "-" << endl; break; case '*': previousIsANum = false; cout << "*" << endl; break; case '/': previousIsANum = false; cout << "/" << endl; break; default: break; } } char i = ' '; while (stack->ltopOfStack > 0){ stack->cmstackPop(i); output->cmstackPush(i); cout << i << endl; } return 0; } Here is the stack code (watch out!): #include <cstdio> #include <assert.h> #include <new.h> #include <stdlib.h> #include <iostream> class ctstack { private: long* lpstack ; // the stack itself long ltrue ; // constructor sets to 1 long lfalse ; // constructor sets to 0 // offset to top of the stack long lmaxEleInStack ; // maximum possible elements of stack public: long ltopOfStack ; ctstack ( long lnbrOfEleToAllocInStack ) { // Constructor lfalse = 0 ; // set to zero ltrue = 1 ; // set to one assert ( lnbrOfEleToAllocInStack > 0 ) ; // assure positive argument ltopOfStack = -1 ; // ltopOfStack is really an index lmaxEleInStack = lnbrOfEleToAllocInStack ; // set lmaxEleInStack to max ele lpstack = new long [ lmaxEleInStack ] ; // allocate stack assert ( lpstack ) ; // assure new succeeded } ~ctstack ( ) { // Destructor delete [ ] lpstack ; // Delete the stack itself } ctstack& operator= ( const ctstack& ctoriginStack) { // Assignment if ( this == &ctoriginStack ) // verify x not assigned to x return *this ; if ( this -> lmaxEleInStack < ctoriginStack . lmaxEleInStack ) { // if destination stack is smaller than delete [ ] this -> lpstack ; // original stack, delete dest and alloc this -> lpstack = // sufficient memory new long [ ctoriginStack . lmaxEleInStack ] ; assert ( this -> lpstack ) ; // assure new succeeded // reset stack size attribute this -> lmaxEleInStack = ctoriginStack . lmaxEleInStack ; } // copy original to destination stack for ( long i = 0 ; i < ctoriginStack . lmaxEleInStack ; i ++ ) *( this -> lpstack + i ) = *( ctoriginStack . lpstack + i ) ; this -> ltopOfStack = ctoriginStack . ltopOfStack ; // reset stack position attribute return *this ; } long cmstackPush (char lplaceInStack ) { // Push Method if ( ltopOfStack == lmaxEleInStack - 1 ) // stack is full can't add element return lfalse ; ltopOfStack ++ ; // acquire free slot *(lpstack + ltopOfStack ) = lplaceInStack ; // add element return ltrue ; // any number other than zero is true } long cmstackPop (char& lretrievedStackEle ) { // Pop Method if ( ltopOfStack < 0 ) { // stack has no elements lretrievedStackEle = -1 ; // dummy element return lfalse ; } lretrievedStackEle = *( lpstack + ltopOfStack ) ; // stack has element -- return it ltopOfStack -- ; // stack is pop'd return ltrue ; // any number other than zero is true } long cmstackLookAtTop (char& lretrievedStackEle ) { // Pop Method if ( ltopOfStack < 0 ) { // stack has no elements lretrievedStackEle = -1 ; // dummy element return lfalse ; } lretrievedStackEle = *( lpstack + ltopOfStack ) ; // stack has element -- return it return ltrue ; // any number other than zero is true } long cmstackHasAnEle (char& lretrievedTopOfStack ) { // Has element method lretrievedTopOfStack = ltopOfStack ; return ltopOfStack < 0 ? lfalse : ltrue ; // 0 - false stack does not have any ele } // 1 - true stack has at least one element long cmstackMaxNbrOfEle (char& lretrievedMaxStackEle ) { // Maximum element method lretrievedMaxStackEle = lmaxEleInStack ; // return stack size in reference var return ltrue ; // Return Maximum Size of Stack } } ; Thanks, Anthony.

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  • Sub-Zero’s Glasses Get Broken [Video]

    - by Asian Angel
    Sub-Zero and Liu Kang are in the middle of a serious round of combat when an unexpected problem occurs. Sub-Zero apparently decided to keep his glasses in his pocket and one bicycle kick later they are history. Will this be the only problem to occur during the fight or are things going to get worse? Sub-Zero’s Glasses Are Broken [Dorkly] HTG Explains: What Is Windows RT and What Does It Mean To Me? HTG Explains: How Windows 8′s Secure Boot Feature Works & What It Means for Linux Hack Your Kindle for Easy Font Customization

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  • Problems with Android Fragment back stack

    - by DexterMoon
    I've got a massive problem with the way the android fragment backstack seems to work and would be most grateful for any help that is offered. Imagine you have 3 Fragments [1] [2] [3] I want the user to be able to navigate [1] > [2] > [3] but on the way back (pressing back button) [3] > [1]. As I would have imagined this would be accomplished by not calling addToBackStack(..) when creating the transaction that brings fragment [2] into the fragment holder defined in XML. The reality of this seems as though that if I dont want [2] to appear again when user presses back button on [3], I must not call addToBackStack in the transaction that shows fragment [3]. This seems completely counter-intuitive (perhaps coming from the iOS world). Anyway if i do it this way, when I go from [1] > [2] and press back I arrive back at [1] as expected. If I go [1] > [2] > [3] and then press back I jump back to [1] (as expected). Now the strange behavior happens when I try and jump to [2] again from [1]. First of all [3] is briefly displayed before [2] comes into view. If I press back at this point [3] is displayed, and if I press back once again the app exits. Can anyone help me to understand whats going on here? And here is the layout xml file for my main activity: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical" > <fragment android:id="@+id/headerFragment" android:layout_width="match_parent" android:layout_height="wrap_content" class="com.fragment_test.FragmentControls" > <!-- Preview: layout=@layout/details --> </fragment> <FrameLayout android:id="@+id/detailFragment" android:layout_width="match_parent" android:layout_height="fill_parent" /> Update This is the code I'm using to build by nav heirarchy Fragment frag; FragmentTransaction transaction; //Create The first fragment [1], add it to the view, BUT Dont add the transaction to the backstack frag = new Fragment1(); transaction = getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.detailFragment, frag); transaction.commit(); //Create the second [2] fragment, add it to the view and add the transaction that replaces the first fragment to the backstack frag = new Fragment2(); transaction = getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.detailFragment, frag); transaction.addToBackStack(null); transaction.commit(); //Create third fragment frag = new Fragment3(); transaction = getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.detailFragment, frag); transaction.commit(); //END OF SETUP CODE------------------------- //NOW: //Press back once and then issue the following code: frag = new Fragment2(); transaction = getSupportFragmentManager().beginTransaction(); transaction.replace(R.id.detailFragment, frag); transaction.addToBackStack(null); transaction.commit(); //Now press back again and you end up at fragment [3] not [1] Many thanks

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  • Gateway IP Returns to Zero

    - by Robert Smith
    When you set a static IP under Ubuntu 12.04.1, you must supply the desired machine IP and the gateway IP, all using the Network Manager. When I first entered them and rebooted, everything worked great. On the second boot, however, Firefox could find no Web page. Upon checking, I discovered that the gateway IP had returned to zero. Now, no matter how often I resupply it, it returns to zero immediately after NM "saves" it: that is, appears as zero when redisplayed. The only way I can get to the Internet is to restore DHCP operation. I need to use static IP for access to my home network. Would appreciate any suggestion. --Robert Smith

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  • Should integer divide by zero halt execution?

    - by Pyrolistical
    I know that modern languages handle integer divide by zero as an error just like the hardware does, but what if we could design a whole new language? Ignoring existing hardware, what should a programming language does when an integer divide by zero occurs? Should it return a NaN of type integer? Or should it mirror IEEE 754 float and return +/- Infinity? Or is the existing design choice correct, and an error should be thrown? Is there a language that handles integer divide by zero nicely? EDIT When I said ignore existing hardware, I mean don't assume integer is represented as 32 bits, it can be represented in anyway you can to imagine.

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  • Class members allocation on heap/stack? C++

    - by simplebutperfect
    If a class is declared as follows: class MyClass { char * MyMember; MyClass() { MyMember = new char[250]; } ~MyClass() { delete[] MyMember; } }; And it could be done like this: class MyClass { char MyMember[250]; }; How does a class gets allocated on heap, like if i do MyClass * Mine = new MyClass(); Does the allocated memory also allocates the 250 bytes in the second example along with the class instantiation? And will the member be valid for the whole lifetime of MyClass object? As for the first example, is it practical to allocate class members on heap?

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  • gdb stack strangeness

    - by aaa
    Hi I get this weird backtrace (sometimes): (gdb) bt #0 0x00002b36465a5d4c in AY16_Loop_M16 () from /opt/intel/mkl/10.0.3.020/lib/em64t/libmkl_mc.so #1 0x00000000000021da in ?? () #2 0x00000000000021da in ?? () #3 0xbf3e9dec2f04aeff in ?? () #4 0xbf480541bd29306a in ?? () #5 0xbf3e6017955273e8 in ?? () #6 0xbf442b937c2c1f37 in ?? () #7 0x3f5580165832d744 in ?? () ... Any ideas why i cant see the symbols? Compiled with debugging syms of course. The same session gives symbols at other points.

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  • Android NDK Gaussian Blur radius stuck at 60

    - by rennoDeniro
    I implemented this NDK imeplementation of a Gaussian Blur, But I am having problems. I cannot increase the radius above 60, otherwise the activity just closes returning to a previous activity. No error message, nothing? Does anyone know why this could be? Note: This blur is based on the quasimondo implementation, here #include <jni.h> #include <string.h> #include <math.h> #include <stdio.h> #include <android/log.h> #include <android/bitmap.h> #define LOG_TAG "libbitmaputils" #define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__) #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__) typedef struct { uint8_t red; uint8_t green; uint8_t blue; uint8_t alpha; } rgba; JNIEXPORT void JNICALL Java_com_insert_your_package_ClassName_functionToBlur(JNIEnv* env, jobject obj, jobject bitmapIn, jobject bitmapOut, jint radius) { LOGI("Blurring bitmap..."); // Properties AndroidBitmapInfo infoIn; void* pixelsIn; AndroidBitmapInfo infoOut; void* pixelsOut; int ret; // Get image info if ((ret = AndroidBitmap_getInfo(env, bitmapIn, &infoIn)) < 0 || (ret = AndroidBitmap_getInfo(env, bitmapOut, &infoOut)) < 0) { LOGE("AndroidBitmap_getInfo() failed ! error=%d", ret); return; } // Check image if (infoIn.format != ANDROID_BITMAP_FORMAT_RGBA_8888 || infoOut.format != ANDROID_BITMAP_FORMAT_RGBA_8888) { LOGE("Bitmap format is not RGBA_8888!"); LOGE("==> %d %d", infoIn.format, infoOut.format); return; } // Lock all images if ((ret = AndroidBitmap_lockPixels(env, bitmapIn, &pixelsIn)) < 0 || (ret = AndroidBitmap_lockPixels(env, bitmapOut, &pixelsOut)) < 0) { LOGE("AndroidBitmap_lockPixels() failed ! error=%d", ret); } int h = infoIn.height; int w = infoIn.width; LOGI("Image size is: %i %i", w, h); rgba* input = (rgba*) pixelsIn; rgba* output = (rgba*) pixelsOut; int wm = w - 1; int hm = h - 1; int wh = w * h; int whMax = max(w, h); int div = radius + radius + 1; int r[wh]; int g[wh]; int b[wh]; int rsum, gsum, bsum, x, y, i, yp, yi, yw; rgba p; int vmin[whMax]; int divsum = (div + 1) >> 1; divsum *= divsum; int dv[256 * divsum]; for (i = 0; i < 256 * divsum; i++) { dv[i] = (i / divsum); } yw = yi = 0; int stack[div][3]; int stackpointer; int stackstart; int rbs; int ir; int ip; int r1 = radius + 1; int routsum, goutsum, boutsum; int rinsum, ginsum, binsum; for (y = 0; y < h; y++) { rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0; for (i = -radius; i <= radius; i++) { p = input[yi + min(wm, max(i, 0))]; ir = i + radius; // same as sir stack[ir][0] = p.red; stack[ir][1] = p.green; stack[ir][2] = p.blue; rbs = r1 - abs(i); rsum += stack[ir][0] * rbs; gsum += stack[ir][1] * rbs; bsum += stack[ir][2] * rbs; if (i > 0) { rinsum += stack[ir][0]; ginsum += stack[ir][1]; binsum += stack[ir][2]; } else { routsum += stack[ir][0]; goutsum += stack[ir][1]; boutsum += stack[ir][2]; } } stackpointer = radius; for (x = 0; x < w; x++) { r[yi] = dv[rsum]; g[yi] = dv[gsum]; b[yi] = dv[bsum]; rsum -= routsum; gsum -= goutsum; bsum -= boutsum; stackstart = stackpointer - radius + div; ir = stackstart % div; // same as sir routsum -= stack[ir][0]; goutsum -= stack[ir][1]; boutsum -= stack[ir][2]; if (y == 0) { vmin[x] = min(x + radius + 1, wm); } p = input[yw + vmin[x]]; stack[ir][0] = p.red; stack[ir][1] = p.green; stack[ir][2] = p.blue; rinsum += stack[ir][0]; ginsum += stack[ir][1]; binsum += stack[ir][2]; rsum += rinsum; gsum += ginsum; bsum += binsum; stackpointer = (stackpointer + 1) % div; ir = (stackpointer) % div; // same as sir routsum += stack[ir][0]; goutsum += stack[ir][1]; boutsum += stack[ir][2]; rinsum -= stack[ir][0]; ginsum -= stack[ir][1]; binsum -= stack[ir][2]; yi++; } yw += w; } for (x = 0; x < w; x++) { rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0; yp = -radius * w; for (i = -radius; i <= radius; i++) { yi = max(0, yp) + x; ir = i + radius; // same as sir stack[ir][0] = r[yi]; stack[ir][1] = g[yi]; stack[ir][2] = b[yi]; rbs = r1 - abs(i); rsum += r[yi] * rbs; gsum += g[yi] * rbs; bsum += b[yi] * rbs; if (i > 0) { rinsum += stack[ir][0]; ginsum += stack[ir][1]; binsum += stack[ir][2]; } else { routsum += stack[ir][0]; goutsum += stack[ir][1]; boutsum += stack[ir][2]; } if (i < hm) { yp += w; } } yi = x; stackpointer = radius; for (y = 0; y < h; y++) { output[yi].red = dv[rsum]; output[yi].green = dv[gsum]; output[yi].blue = dv[bsum]; rsum -= routsum; gsum -= goutsum; bsum -= boutsum; stackstart = stackpointer - radius + div; ir = stackstart % div; // same as sir routsum -= stack[ir][0]; goutsum -= stack[ir][1]; boutsum -= stack[ir][2]; if (x == 0) vmin[y] = min(y + r1, hm) * w; ip = x + vmin[y]; stack[ir][0] = r[ip]; stack[ir][1] = g[ip]; stack[ir][2] = b[ip]; rinsum += stack[ir][0]; ginsum += stack[ir][1]; binsum += stack[ir][2]; rsum += rinsum; gsum += ginsum; bsum += binsum; stackpointer = (stackpointer + 1) % div; ir = stackpointer; // same as sir routsum += stack[ir][0]; goutsum += stack[ir][1]; boutsum += stack[ir][2]; rinsum -= stack[ir][0]; ginsum -= stack[ir][1]; binsum -= stack[ir][2]; yi += w; } } // Unlocks everything AndroidBitmap_unlockPixels(env, bitmapIn); AndroidBitmap_unlockPixels(env, bitmapOut); LOGI ("Bitmap blurred."); } int min(int a, int b) { return a > b ? b : a; } int max(int a, int b) { return a > b ? a : b; }

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  • Enum types, FlagAttribute & Zero value

    - by nmgomes
    We all know about Enums types and use them every single day. What is not that often used is to decorate the Enum type with the FlagsAttribute. When an Enum type has the FlagsAttribute we can assign multiple values to it and thus combine multiple information into a single enum. The enum values should be a power of two so that a bit set is achieved. Here is a typical Enum type: public enum OperationMode { /// <summary> /// No operation mode /// </summary> None = 0, /// <summary> /// Standard operation mode /// </summary> Standard = 1, /// <summary> /// Accept bubble requests mode /// </summary> Parent = 2 } In such scenario no values combination are possible. In the following scenario a default operation mode exists and combination is used: [Flags] public enum OperationMode { /// <summary> /// Asynchronous operation mode /// </summary> Async = 0, /// <summary> /// Synchronous operation mode /// </summary> Sync = 1, /// <summary> /// Accept bubble requests mode /// </summary> Parent = 2 } Now, it’s possible to do statements like: [DefaultValue(OperationMode.Async)] [TypeConverter(typeof(EnumConverter))] public OperationMode Mode { get; set; } /// <summary> /// Gets a value indicating whether this instance supports request from childrens. /// </summary> public bool IsParent { get { return (this.Mode & OperationMode.Parent) == OperationMode.Parent; } } or switch (this.Mode) { case OperationMode.Sync | OperationMode.Parent: Console.WriteLine("Sync,Parent"); break;[…]  But there is something that you should never forget: Zero is the absorber element for the bitwise AND operation. So, checking for OperationMode.Async (the Zero value) mode just like the OperationMode.Parent mode makes no sense since it will always be true: (this.Mode & 0x0) == 0x0 Instead, inverse logic should be used: OperationMode.Async = !OperationMode.Sync public bool IsAsync { get { return (this.Mode & ContentManagerOperationMode.Sync) != ContentManagerOperationMode.Sync; } } or public bool IsAsync { get { return (int)this.Mode == 0; } } Final Note: Benefits Allow multiple values combination The above samples snippets were taken from an ASP.NET control and enabled the following markup usage: <my:Control runat="server" Mode="Sync,Parent"> Drawback Zero value is the absorber element for the bitwise AND operation Be very carefully when evaluating the Zero value, either evaluate the enum value as an integer or use inverse logic.

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