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• const ready only local copies

  - by robUK

  Hello gcc 4.4.4 c89 I am just wondering is it worth passing a const into a function. i.e. void do_something(const char *dest, const int size) The size is a ready-only so I don't want to change it. However, some developers never have this as const has it is a local copy that is being used. The pointer is const as you can change the value in the calling routine. I always have a const on ready-only local copies, as it confirms to anyone reading my code that it is a ready-only variable. And also, when coding I don't make the mistake of changing it without realizing. Many thanks for any suggestions,

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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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• Pointers in For loops

  - by Bobby

  Quick question: I am a C# guy debugging a C++ app so I am not used to memory management. In the following code: for(int i = 0; i < TlmMsgDB.CMTGetTelemMsgDBCount(); i++) { CMTTelemetryMsgCls* telm = TlmMsgDB.CMTGetTelemetryMsg(i); CMT_SINT32_Tdef id = telm->CMTGetPackingMapID(); ManualScheduleTables.SetManualMsg(i,id); ManualScheduleTables.SetManExec(i,false); } Am I leaking memory every iteration b/c of CMTTelemetryMsgCls* telm = TlmMsgDB.CMTGetTelemetryMsg(i);? The "CMTGetTelemetryMsg(int)" method returns a pointer. Do I have to "delete telm;" at the end of each iteration?

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• CSS menu is flickering when scrolling through it with hover effects

  - by kritop

  I hope i described the problem well!? You can see it here: http://dealmob.de/index_dev.html when u hover over the menu up and down fast u see the that its not staying, insteads its flickering like you would change the margins/paddings by few pixels. Any advice on how to solve this problem? thanks a lot like requested: #topcities { float:right; } #topcities li { padding-left:5px; width:100px; } #topcities li:hover { cursor:pointer; color:#000; background: url(images/hover_menue_back.jpg) repeat-x #FFF; -moz-border-radius: 5px; -webkit-border-radius: 5px; border:grey 1px solid; width:100px; }

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• What is the role of asserts in C++ programs that have unit tests?

  - by lhumongous

  Greetings, I've been adding unit tests to some legacy C++ code, and I've run into many scenarios where an assert inside a function will get tripped during a unit test run. A common idiom that I've run across is functions that take pointer arguments and immediately assert if the argument is NULL. I could easily get around this by disabling asserts when I'm unit testing. But I'm starting to wonder if unit tests are supposed to alleviate the need for runtime asserts. Is this a correct assessment? Are unit tests supposed to replace runtime asserts by happening sooner in the pipeline (ie: the error is caught in a failing test instead of when the program is running). On the other hand, I don't like adding soft fails to code (eg: if(param == NULL) return false;). A runtime assert at least makes it easier to debug a problem in case a unit test missed a bug. Thanks!

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• Simple C++ container class that is thread-safe for writing

  - by conradlee

  I am writing a multi-threaded program using OpenMP in C++. At one point my program forks into many threads, each of which need to add "jobs" to some container that keeps track of all added jobs. Each job can just be a pointer to some object. Basically, I just need the add pointers to some container from several threads at the same time. Is there a simple solution that performs well? After some googling, I found that STL containers are not thread-safe. Some stackoverflow threads address this question, but none that forms a consensus on a simple solution.

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• How do IOS know which viewController is being viewed and hence need viewWillAppear to be called

  - by Jim Thio

  How does iOs know? Does each view has a pointer to it's controller? What happened? When we pop a viewController from navigation, does the navigationController arrange which view should be called? For example: If I added: [[BNUtilitiesQuick window] addSubview:[BNUtilitiesQuick searchController].view]; viewWillAppear will be called. However, window doesn't know the viewController. I am passing the view outlet of the controller not the controller. How can iOs 5 knows that it has to call [[BNUtilitiesQuick searchController] viewWillAppear:YES]

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• UML binary association aggregatee has access to aggregator

  - by user314172

  Firstly, I'd like to thank those who answered my previous question ages ago. Currently I'm engaging more in the design phase UMLs, as this is my first medium scale deployment I'm entrusted with. This is extremely simple, but it bugs me so. If (Component) owns (Manager of Component), and (Manager of Component) has a reference to (Component) through which it manages it; how do you fully describe the relationship? I know it is aggregative, but how do you describe (Manager of Component) possessing a reference/pointer to the (Component) that physically owns the (Manager of Component) ? Example: Lidar owns a LidarManager

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• Passing around objects to network packet handlers ?

  - by xeross

  Hey, I've been writing a networking server for a while now in C++ and have come to the stage to start looking for a way to properly and easily handle all packets. I am so far that I can figure out what kind of packet it is, but now I need to figure out how to get the needed data to the handler functions. I had the following in mind: Have a map of function pointers with the opcode as key and the function pointer as value Have all these functions have 2 arguments, packet and ObjectAccessor ObjectAccessor class contains various functions to fetch various items such as users and alike Perhaps pass the user's guid too so we can fetch it from the objectaccessor I'd like to know the various implementations others have come up with, so please comment on this idea and reply with your own implementations. Thanks, Xeross

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• Shell script exiting the loop after calling another script

  - by Johnyy

  Hi Guys, I have a shell script s1 calling another script s2 in a loop. However s1 can not seem to continue the loop after s2 returns. Commenting out the line that calls s2 will enable the loop to continue. s2 does copy of one file, s1 checks conditions and copy several files using s2. Can anyone give a pointer what is going on here? ... while read line s2 param1 param2 param3 echo "copy done" done < $tempfile echo "out of loop" ... "copy done" is printed, so is "out of loop"

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• What is the logic behind defining macros inside a struct?

  - by systemsfault

  As apparent in the title, I'm questioning the reason behind defining the macros inside a struct. I frequently see this approach in network programming for instance following snippet: struct sniff_tcp { u_short th_sport; /* source port */ u_short th_dport; /* destination port */ tcp_seq th_seq; /* sequence number */ tcp_seq th_ack; /* acknowledgement number */ u_char th_offx2; /* data offset, rsvd */ #define TH_OFF(th) (((th)->th_offx2 & 0xf0) >> 4) u_char th_flags; #define TH_FIN 0x01 #define TH_SYN 0x02 #define TH_RST 0x04 #define TH_PUSH 0x08 #define TH_ACK 0x10 #define TH_URG 0x20 #define TH_ECE 0x40 #define TH_CWR 0x80 #define TH_FLAGS (TH_FIN|TH_SYN|TH_RST|TH_ACK|TH_URG|TH_ECE|TH_CWR) u_short th_win; /* window */ u_short th_sum; /* checksum */ u_short th_urp; /* urgent pointer */ }; This example is from sniffex.c code in tcpdump's web site. Is this for enhancing readability and making code clearer.

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• casting issue with realpath function (c programming)

  - by Ralph

  When I compile the following code: #define _POSIX_C_SOURCE 200112L #define _ISOC99_SOURCE #define __EXTENSIONS__ #include <stdio.h> #include <limits.h> #include <stdlib.h> int main(int argc, char *argv[]) { char *symlinkpath = argv[1]; char actualpath [PATH_MAX]; char *ptr; ptr = realpath(symlinkpath, actualpath); printf("%s\n", ptr); } I get a warning on the line that contains the call to the realpath function, saying: warning: assignment makes pointer from integer without a cast Anybody know what's up? I'm running Ubuntu Linux 9.04

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• Text indent is not working in ie7

  - by saorabh

  I am working on a website and on the top navigation bar there is a search box, I applied the following css on the search submit button #submit{background:url("img/new-search-icon.png") no-repeat scroll -1px 0 #FFFFFF; border:0 none; cursor:pointer; display:block; height:21px; padding:0; position:absolute; right:0; text-indent:-9999px; top:0; width:20px; z-index:2;} My Problem is in IE7 the text indent is not working please help me if you want to see the demo you can view it by clicking here Click here. Please help me.

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• overflow technique in stack

  - by metashockwave

  int main(void) { problem2(); } void doit2(void) { int overflowme[16]; //overflowme[37] =0; } void problem2(void) { int x = 42; doit2(); printf("x is %d\n", x); printf("the address of x is 0x%x\n", &x); } Would someone help me understand why overflowme[37] =0; from the doit2 function will overwrite the value of x? (please include Program Counter and Frame Pointer of the function doit2 in your explanation) Thank you! It works every time with Project properties-Configuration properties-C/C++ -Code Generation-Basic Runtime Checks set to "Default". so it's not an undefined behavior.

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• Manipulating both unicode and ASCII character set in C#

  - by Murlex

  I have this mapping in my C# application string [,] unicode2Ascii = { { "&#3001;", "\x86" } }; ஹ - is the unicode value for a tamil literal "ஹ". This is the raw hex literal for the unicode value saved by MS Word as a byte sequence. I am trying to map these unicode value "strings" to a hex value under 255 (so as to accommodate non-unicode supported systems). I trying to use string.replace like this: S = S.replace(unicode2Ascii[0,0], unicode2Ascii[0,1]); However the resultant ouput has a ? instead of the actual hex 0x86 stored. Any pointer on how I could set the encoding for the second element of that array to something like windows-1252? Or is there a better way to do this conversion? thanks in advance

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• Which tool can list writing access to a specific variable in C?

  - by Lichtblitz

  Unfortunately I'm not even sure how this sort of static analysis is called. It's not really control flow analysis because I'm not looking for function calls and I don't really need data flow analysis because I don't care about the actual values. I just need a tool that lists the locations (file, function) where writing access to a specific variable takes place. I don't even care if that list contained lines that are unreachable. I could imagine that writing a simple parser could suffice for this task but I'm certain that there must be a tool out there that does this simple analysis. As a poor student I would appreciate free or better yet open source tools and if someone could tell me how this type of static analysis is actually called, I would be equally grateful! EDIT: I forgot to mention there's no pointer arithmetic in the code base.

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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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• What's the difference between initializing this structure with these strategies?

  - by mystify

  // the malloc style, which returns a pointer: struct Cat *newCat = malloc(sizeof(struct Cat)); // no malloc...but isn't it actually the same thing? uses memory as well, or not? struct Cat cat = {520.0f, 680.0f, NULL}; Basically, I can get a initialized structure in these two ways. My guess is: It's the same thing, but when I use malloc I also have to free() that. In the second case I don't have to think about memory, because I don't call malloc. Maybe. When should I use the malloc style, and when the other?

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• HRESULT exception not caught in VS 2008

  - by arionik

  Hello all, I've got a stange situation in visual studio 2008 C++. I work on code that was originally written for visual studio 2003, where everything works well. Now, ported to VS 2008, the exception handling, which unfortuantely exists widely in the code, does not work anymore. standard code example: try { HRESULT hr = S_OK; // do stuff... if( FAILED( hr ) ) throw hr; } catch( HRESULT hr ) { // error handling, but we never get here } catch( ... ) { // ... not even here } Under VS 2008, no exception is encountered, but I get a crash somewhere else, indicating that the stack pointer must be screwed up. Did anybody come across this behaviour? Any help is appreciated.

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• AS2: How do I swapDepth of a Shape and a TextField?

  - by Alex Jordan

  AS2 this.createTextField("lbl_txt", this.getNextHighestDepth(), 70, 5, 150, 30) lbl_txt.autoSize = true; lbl_txt.text = "Hello"; var fmt:TextFormat = new TextFormat(); fmt.bold = true; fmt.color = 0x000000; fmt.underline = true; fmt.font = "Arial"; lbl_txt.setTextFormat(fmt); Timeline Layers action button_layer (button_layer is a animation on rollOver) arrow background Desired Result button_layer and action to be topmost layers and cursor to remain a pointer and not switch to text cursor on rollOver. action button_layer arrow lbl_txt (TextField created by AS) background

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• c++: truth assignment warning with arguments?

  - by John

  I use the following to work with arguments in my programs, but it seems to just hand me a warning (just a warning): "warning: suggest parentheses around assignment used as truth value" The beginning of the code is as follows: enum{OPT_DISP_H = 0x2, OPT_DISP_W = 0x1}; int main(int argc, char *argv[]) { int opt = 0x00; char c; while((++argv)[0] && argv[0][0]=='-'){ while(c =* ++argv[0]) switch(c){ case 'h': opt |= OPT_DISP_H; break; //etc.. The while(c =* ++argv[0]) part being where the warning persists. The code works fine, but what does this warning mean opposed to what is used? I think the code is c = *++argv[0], using the pointer. So why does the single = work and what is really recommended to be used?

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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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• I serialized a C++ object, how to allocate memory for it without knowing what type it is?

  - by Neo_b

  Hello, I have serialized a C++ object and I wish to allocate space for it, although I can't use the "new" operator, because I do not know the object's class. I tried using malloc(sizeof(object)), although trying to typecast the pointer to the type the serialized object is of, the program shut down. Where is the information about the object class stored? class object { public: virtual void somefunc(); int someint; }; class objectchild:public object { } object *o=(object*)malloc(sizeof(objectchild)); cout << int(dynamic_cast<objectchild*>(o)) << endl; This causes a program shutdown. Thank you in advance.

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• Printf ubuntu Segmentation fault (core dumped)

  - by Someone

  I have this code: int a; printf("&a = %u\n",(unsigned)&a); printf("a\n"); printf("b\n"); printf("c\n"); printf("d\n"); I tried to print the pointer of a variable. But it fail on the row printf("a\n"); and says Segmentation fault (core dumped) Output: &a = 134525024 Segmentation fault (core dumped) When I remove the row printf("&a = %u\n",(unsigned)&a); from the code, its success. Output: a b c d What worng in my code?

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• HTML5 placing image where i want it on screen

  - by corrigan_sam

  I have a little start screen running and i want the image, which is acting as a button, to placed at a certain point, but when i try to it stays in the same place, and i don't know how i can get it to stay in the place i want it. Here is my code, its is HTML with some css: <style> #SplashScreen{ position:relative; overflow:hidden; } #StartButton { cursor:pointer; position:absoloute; left:100px; top:100px; } </style> <div id="SplashScreen" width="400" height="400"> <h1>Game Title</h1> <img id="StartButton" src="play.png"/> </div> The image just draws underneath the title and not where i want it. Any help?

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