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  • What's the performance penalty of weak_ptr?

    - by Kornel Kisielewicz
    I'm currently designing a object structure for a game, and the most natural organization in my case became a tree. Being a great fan of smart pointers I use shared_ptr's exclusively. However, in this case, the children in the tree will need access to it's parent (example -- beings on map need to be able to access map data -- ergo the data of their parents. The direction of owning is of course that a map owns it's beings, so holds shared pointers to them. To access the map data from within a being we however need a pointer to the parent -- the smart pointer way is to use a reference, ergo a weak_ptr. However, I once read that locking a weak_ptr is a expensive operation -- maybe that's not true anymore -- but considering that the weak_ptr will be locked very often, I'm concerned that this design is doomed with poor performance. Hence the question: What is the performance penalty of locking a weak_ptr? How significant is it?

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  • Primary reasons why programming language runtimes use stacks?

    - by manuel aldana
    Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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  • grdb not working variables

    - by stupid_idiot
    hi, i know this is kinda retarded but I just can't figure it out. I'm debugging this: xor eax,eax mov ah,[var1] mov al,[var2] call addition stop: jmp stop var1: db 5 var2: db 6 addition: add ah,al ret the numbers that I find on addresses var1 and var2 are 0x0E and 0x07. I know it's not segmented, but that ain't reason for it to do such escapades, because the addition call works just fine. Could you please explain to me where is my mistake? I see the problem, dunno how to fix it yet though. The thing is, for some reason the instruction pointer starts at 0x100 and all the segment registers at 0x1628. To address the instruction the used combination is i guess [cs:ip] (one of the segment registers and the instruction pointer for sure). The offset to var1 is 0x10 (probably because from the begining of the code it's the 0x10th byte in order), i tried to examine the memory and what i got was: 1628:100 8 bytes 1628:108 8 bytes 1628:110 <- wtf? (assume another 8 bytes) 1628:118 ... whatever tricks are there in the memory [cs:var1] points somewhere else than in my code, which is probably where the label .data would usually address ds.... probably.. i don't know what is supposed to be at 1628:10 ok, i found out what caused the assness and wasted me whole fuckin day. the behaviour described above is just correct, the code is fully functional. what i didn't know is that grdb debugger for some reason sets the begining address to 0x100... the sollution is to insert the directive ORG 0x100 on the first line and that's the whole thing. the code was working because instruction pointer has the right address to first instruction and goes one by one, but your assembler doesn't know what effective address will be your program stored at so it pretty much remains relative to first line of the code which means all the variables (if not using label for data section) will remain pointing as if it started at 0x0. which of course wouldn't work with DOS. and grdb apparently emulates some DOS features... sry for the language, thx everyone for effort, hope this will spare someone's time if having the same problem... heheh.. at least now i know the reason why to use .data section :))))

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  • Silencing GCC warnings when using an "Uncopyable" class

    - by Kazade
    I have several classes that I don't want to be copyable, some of these classes have pointer data members. To make these classes uncopyable I privately inherit the following class template: template <class T> class Uncopyable { protected: Uncopyable() {} virtual ~Uncopyable() {} private: Uncopyable(const Uncopyable &); T & operator=(const T&); }; Which I used like so: class Entity : private Uncopyable<Entity> { } This works fine, however when I compile with -Weffc++ I still get the following warning: class Entity has pointer data members but does not override Entity(const Entity&) or operator=(const Entity&) Why is it still giving me this warning?

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  • Is there a way to use template specialization to separate new from new[]?

    - by Marlon
    I have an auto pointer class and in the constructor I am passing in a pointer. I want to be able to separate new from new[] in the constructor so that I can properly call delete or delete[] in the destructor. Can this be done through template specialization? I don't want to have to pass in a boolean in the constructor. template <typename T> class MyAutoPtr { public: MyAutoPtr(T* aPtr); }; // in use: MyAutoPtr<int> ptr(new int); MyAutoPtr<int> ptr2(new int[10]);

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  • Program crash for array copy with ifort

    - by Stefano Borini
    This program crashes with Illegal instruction: 4 on MacOSX Lion and ifort (IFORT) 12.1.0 20111011 program foo real, pointer :: a(:,:), b(:,:) allocate(a(5400, 5400)) allocate(b(5400, 3600)) a=1.0 b(:, 1:3600) = a(:, 1:3600) print *, a print *, b deallocate(a) deallocate(b) end program The same program works with gfortran. I don't see any problem. Any ideas ? Unrolling the copy and performing the explicit loop over the columns works in both compilers. Note that with allocatable instead of pointer I have no problems. The behavior is the same if the statement is either inside a module or not. I confirm the same behavior on Linux using ifort (IFORT) 12.1.3 20120130.

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  • C++ inheritance and member function pointers

    - by smh
    In C++, can member function pointers be used to point to derived (or even base) class members? EDIT: Perhaps an example will help. Suppose we have a hierarchy of three classes X, Y, Z in order of inheritance. Y therefore has a base class X and a derived class Z. Now we can define a member function pointer p for class Y. This is written as: void (Y::*p)(); (For simplicity, I'll assume we're only interested in functions with the signature void f() ) This pointer p can now be used to point to member functions of class Y. This question (two questions, really) is then: Can p be used to point to a function in the derived class Z? Can p be used to point to a function in the base class X?

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  • Inheritance - initialization problem

    - by dumbquestion
    I have a c++ class derived from a base class in a framework. The derived class doesn't have any data members because I need it to be freely convertible into a base class and back - the framework is responsible for loading and saving the objects and I can't change it. My derived class just has functions for accessing the data. But there are a couple of places where I need to store some temporary local variables to speed up access to data in the base class. mydata* MyClass::getData() { if ( !m_mydata ) { // set to NULL in the constructor m_mydata = some_long_and complex_operation_to_get_the_data_in_the_base() } return m_mydata; } The problem is if I just access the object by casting the base class pointer returned from the framework to MyClass* the ctor for MyClass is never called and m_mydata is junk. Is there a way of only initializing the m_mydata pointer once?

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  • How to approach copying objects with smart pointers as class attributes?

    - by tomislav-maric
    From the boost library documentation I read this: Conceptually, smart pointers are seen as owning the object pointed to, and thus responsible for deletion of the object when it is no longer needed. I have a very simple problem: I want to use RAII for pointer attributes of a class that is Copyable and Assignable. The copy and assignment operations should be deep: every object should have its own copy of the actual data. Also, RTTI needs to be available for the attributes (their type may also be determined at runtime). Should I be searching for an implementation of a Copyable smart pointer (the data are small, so I don't need Copy on Write pointers), or do I delegate the copy operation to the copy constructors of my objects as shown in this answer? Which smart pointer do I choose for simple RAII of a class that is copyable and assignable? (I'm thinking that the unique_ptr with delegated copy/assignment operations to the class copy constructor and assignment operator would make a proper choice, but I am not sure) Here's a pseudocode for the problem using raw pointers, it's just a problem description, not a running C++ code: // Operation interface class ModelOperation { public: virtual void operate = (); }; // Implementation of an operation called Special class SpecialModelOperation : public ModelOperation { private: // Private attributes are present here in a real implementation. public: // Implement operation void operate () {}; }; // All operations conform to ModelOperation interface // These are possible operation names: // class MoreSpecialOperation; // class DifferentOperation; // Concrete model with different operations class MyModel { private: ModelOperation* firstOperation_; ModelOperation* secondOperation_; public: MyModel() : firstOperation_(0), secondOperation_(0) { // Forgetting about run-time type definition from input files here. firstOperation_ = new MoreSpecialOperation(); secondOperation_ = new DifferentOperation(); } void operate() { firstOperation_->operate(); secondOperation_->operate(); } ~MyModel() { delete firstOperation_; firstOperation_ = 0; delete secondOperation_; secondOperation_ = 0; } }; int main() { MyModel modelOne; // Some internal scope { // I want modelTwo to have its own set of copied, not referenced // operations, and at the same time I need RAII to work for it, // as soon as it goes out of scope. MyModel modelTwo (modelOne); } return 0; }

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  • MinMax Heap implementation without an array

    - by user576531
    Hi. I found lots of MinMax Heap implementations, that were storing data in an array. It is realy easy to implement, that is way I am looking for something different. I want to create a MinMax Heap using only elements of the Heap with pointers to left child and right child (and afcourse a key to compare). So the Heap have only pointer to the root object (min level), and a root object have a pointer to his children (max level) and so on. I know how to insert a new object (finding a proper path by using binary represenation of int depending on Heap size), but I don't know how to implement the rest (push up (down) the element, find parent or grandparent). Thx for help

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  • Remove from a std::set<shared_ptr<T>> by T*

    - by Autopulated
    I have a set of shared pointers: std::set<boost::shared_ptr<T>> set; And a pointer: T* p; I would like to efficiently remove the element of set equal to p, but I can't do this with any of the members of set, or any of the standard algorithms, since T* is a completely different type to boost::shared_ptr<T>. A few approaches I can think of are: somehow constructing a new shared_ptr from the pointer that won't take ownership of the pointed to memory (ideal solution, but I can't see how to do this) wrapping / re-implementing shared_ptr so that I can do the above just doing my own binary search over the set Help!

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  • How to use the vtable to determine class type

    - by Alex Silverman
    I was recently on an interview for a position where C/C++ is the primary language and during one question I was told that it's possible to use the vtable to determine which class in a hierarchy a base pointer actually stores. So if, for example you have class A { public: A() {} virtual ~A() {} virtual void method1() {} }; class B : public A { public: B() {} virtual ~B() {} virtual void method1() {} }; and you instantiate A * pFoo = new B(), is it indeed possible to use the vtable to determine whether pFoo contains a pointer to an instance of A or B?

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  • For-Each and Pointers in Java

    - by John
    Ok, so I'm tyring to iterate through an ArrayList and remove a specefic element. However, I am having some trouble using the For-Each like structure. When I run the following code: ArrayList<String> arr = new ArrayList<String>(); //... fill with some values (doesn't really matter) for(String t : arr) { t = " some other value "; //hoping this would change the actual array } for(String t : arr) { System.out.println(t); //however, I still get the same array here } My question in, how can I make 't' a pointer to 'arr' so that I am able to change the values in a for-each loop? I know I could loop through the ArrayList using a different structure, but this one looks so clean and readable, it would just be nice to be able to make 't' a pointer. All comments are appreciated! Even if you say I should just suck it up and use a different construct.

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  • Installation error: INSTALL_FAILED_OLDER_SDK in eclipse

    - by user3014909
    I have an unexpe`ted problem with my Android project. I have a real android device with ice_cream sandwich installed. My app was working fine during the development but after I added a class to the project, I got an error: Installation error: INSTALL_FAILED_OLDER_SDK The problem is that everything is good in the manifest file. The minSdkversion is 8. Here is my manifest file: <?xml version="1.0" encoding="utf-8"?> <manifest xmlns:android="http://schemas.android.com/apk/res/android" package="zabolotnii.pavel.timer" android:versionCode="1" android:versionName="1.0" > <uses-sdk android:minSdkVersion="8" android:targetSdkVersion="18 " /> <application android:allowBackup="true" android:icon="@drawable/ic_launcher" android:label="@string/app_name" android:theme="@style/AppTheme" > <activity android:name="zabolotnii.pavel.timer.TimerActivity" android:label="@string/app_name" > <intent-filter> <action android:name="android.intent.action.MAIN" /> <category android:name="android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest> I don't know, if there is any need to attach the new class ,but I didn't any changes to other code that should led to this error: package zabolotnii.pavel.timer; import android.app.AlertDialog; import android.content.Context; import android.content.DialogInterface; import android.graphics.Paint; import android.graphics.Point; import android.graphics.Rect; import android.graphics.drawable.Drawable; import android.os.Environment; import android.util.DisplayMetrics; import android.util.TypedValue; import android.view.*; import android.widget.*; import java.io.File; import java.io.FilenameFilter; import java.util.*; public class OpenFileDialog extends AlertDialog.Builder { private String currentPath = Environment.getExternalStorageDirectory().getPath(); private List<File> files = new ArrayList<File>(); private TextView title; private ListView listView; private FilenameFilter filenameFilter; private int selectedIndex = -1; private OpenDialogListener listener; private Drawable folderIcon; private Drawable fileIcon; private String accessDeniedMessage; public interface OpenDialogListener { public void OnSelectedFile(String fileName); } private class FileAdapter extends ArrayAdapter<File> { public FileAdapter(Context context, List<File> files) { super(context, android.R.layout.simple_list_item_1, files); } @Override public View getView(int position, View convertView, ViewGroup parent) { TextView view = (TextView) super.getView(position, convertView, parent); File file = getItem(position); if (view != null) { view.setText(file.getName()); if (file.isDirectory()) { setDrawable(view, folderIcon); } else { setDrawable(view, fileIcon); if (selectedIndex == position) view.setBackgroundColor(getContext().getResources().getColor(android.R.color.holo_blue_dark)); else view.setBackgroundColor(getContext().getResources().getColor(android.R.color.transparent)); } } return view; } private void setDrawable(TextView view, Drawable drawable) { if (view != null) { if (drawable != null) { drawable.setBounds(0, 0, 60, 60); view.setCompoundDrawables(drawable, null, null, null); } else { view.setCompoundDrawables(null, null, null, null); } } } } public OpenFileDialog(Context context) { super(context); title = createTitle(context); changeTitle(); LinearLayout linearLayout = createMainLayout(context); linearLayout.addView(createBackItem(context)); listView = createListView(context); linearLayout.addView(listView); setCustomTitle(title) .setView(linearLayout) .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { if (selectedIndex > -1 && listener != null) { listener.OnSelectedFile(listView.getItemAtPosition(selectedIndex).toString()); } } }) .setNegativeButton(android.R.string.cancel, null); } @Override public AlertDialog show() { files.addAll(getFiles(currentPath)); listView.setAdapter(new FileAdapter(getContext(), files)); return super.show(); } public OpenFileDialog setFilter(final String filter) { filenameFilter = new FilenameFilter() { @Override public boolean accept(File file, String fileName) { File tempFile = new File(String.format("%s/%s", file.getPath(), fileName)); if (tempFile.isFile()) return tempFile.getName().matches(filter); return true; } }; return this; } public OpenFileDialog setOpenDialogListener(OpenDialogListener listener) { this.listener = listener; return this; } public OpenFileDialog setFolderIcon(Drawable drawable) { this.folderIcon = drawable; return this; } public OpenFileDialog setFileIcon(Drawable drawable) { this.fileIcon = drawable; return this; } public OpenFileDialog setAccessDeniedMessage(String message) { this.accessDeniedMessage = message; return this; } private static Display getDefaultDisplay(Context context) { return ((WindowManager) context.getSystemService(Context.WINDOW_SERVICE)).getDefaultDisplay(); } private static Point getScreenSize(Context context) { Point screeSize = new Point(); getDefaultDisplay(context).getSize(screeSize); return screeSize; } private static int getLinearLayoutMinHeight(Context context) { return getScreenSize(context).y; } private LinearLayout createMainLayout(Context context) { LinearLayout linearLayout = new LinearLayout(context); linearLayout.setOrientation(LinearLayout.VERTICAL); linearLayout.setMinimumHeight(getLinearLayoutMinHeight(context)); return linearLayout; } private int getItemHeight(Context context) { TypedValue value = new TypedValue(); DisplayMetrics metrics = new DisplayMetrics(); context.getTheme().resolveAttribute(android.R.attr.listPreferredItemHeightSmall, value, true); getDefaultDisplay(context).getMetrics(metrics); return (int) TypedValue.complexToDimension(value.data, metrics); } private TextView createTextView(Context context, int style) { TextView textView = new TextView(context); textView.setTextAppearance(context, style); int itemHeight = getItemHeight(context); textView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, itemHeight)); textView.setMinHeight(itemHeight); textView.setGravity(Gravity.CENTER_VERTICAL); textView.setPadding(15, 0, 0, 0); return textView; } private TextView createTitle(Context context) { TextView textView = createTextView(context, android.R.style.TextAppearance_DeviceDefault_DialogWindowTitle); return textView; } private TextView createBackItem(Context context) { TextView textView = createTextView(context, android.R.style.TextAppearance_DeviceDefault_Small); Drawable drawable = getContext().getResources().getDrawable(android.R.drawable.ic_menu_directions); drawable.setBounds(0, 0, 60, 60); textView.setCompoundDrawables(drawable, null, null, null); textView.setLayoutParams(new ViewGroup.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT)); textView.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View view) { File file = new File(currentPath); File parentDirectory = file.getParentFile(); if (parentDirectory != null) { currentPath = parentDirectory.getPath(); RebuildFiles(((FileAdapter) listView.getAdapter())); } } }); return textView; } public int getTextWidth(String text, Paint paint) { Rect bounds = new Rect(); paint.getTextBounds(text, 0, text.length(), bounds); return bounds.left + bounds.width() + 80; } private void changeTitle() { String titleText = currentPath; int screenWidth = getScreenSize(getContext()).x; int maxWidth = (int) (screenWidth * 0.99); if (getTextWidth(titleText, title.getPaint()) > maxWidth) { while (getTextWidth("..." + titleText, title.getPaint()) > maxWidth) { int start = titleText.indexOf("/", 2); if (start > 0) titleText = titleText.substring(start); else titleText = titleText.substring(2); } title.setText("..." + titleText); } else { title.setText(titleText); } } private List<File> getFiles(String directoryPath) { File directory = new File(directoryPath); List<File> fileList = Arrays.asList(directory.listFiles(filenameFilter)); Collections.sort(fileList, new Comparator<File>() { @Override public int compare(File file, File file2) { if (file.isDirectory() && file2.isFile()) return -1; else if (file.isFile() && file2.isDirectory()) return 1; else return file.getPath().compareTo(file2.getPath()); } }); return fileList; } private void RebuildFiles(ArrayAdapter<File> adapter) { try { List<File> fileList = getFiles(currentPath); files.clear(); selectedIndex = -1; files.addAll(fileList); adapter.notifyDataSetChanged(); changeTitle(); } catch (NullPointerException e) { String message = getContext().getResources().getString(android.R.string.unknownName); if (!accessDeniedMessage.equals("")) message = accessDeniedMessage; Toast.makeText(getContext(), message, Toast.LENGTH_SHORT).show(); } } private ListView createListView(Context context) { ListView listView = new ListView(context); listView.setOnItemClickListener(new AdapterView.OnItemClickListener() { @Override public void onItemClick(AdapterView<?> adapterView, View view, int index, long l) { final ArrayAdapter<File> adapter = (FileAdapter) adapterView.getAdapter(); File file = adapter.getItem(index); if (file.isDirectory()) { currentPath = file.getPath(); RebuildFiles(adapter); } else { if (index != selectedIndex) selectedIndex = index; else selectedIndex = -1; adapter.notifyDataSetChanged(); } } }); return listView; } }

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  • Split text files Accross threads

    - by Kevin
    The problem: I have a few text files (10) with numbers in them on every line. I need to have them split across some threads I create using the pthread library. these threads that are created (worker threads) are to find the largest prime number that gets sent to them (and over all the largest prime from all of the text files). My current thoughts on solutions: I am thinking myself to have two arrays and all of the text files in one array and the other array will contain a binary file that I can read say 1000 lines and send the pointer to the index of that binary file in a struct that contains the id, file pointer, and file position and let it crank through that. a little bit of what I am talking about pthread_create(&threads[index],NULL,calc_sqrt,(void *)threadFields[index]);//Pass struct to each worker Struct: typedef struct threadFields{ int *id, *position; FILE *Fin; }tField; If anyone has any insight or a better solution it would be greatly appreciated Thanks

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  • a nicer way to create structs in a loop

    - by sandra
    Hi guys, I haven't coded in C++ in ages. And recently, I'm trying to work on something involving structs. Like this typedef struct{ int x; int y; } Point; Then in a loop, I'm trying to create new structs and put pointers to them them in a list. Point* p; int i, j; while (condition){ // compute values for i and j with some function... p = new Point; p* = {i, j}; //initialize my struct. list.append(p); //append this pointer to my list. } Now, my question is it possible to simplify this? I mean, the pointer variable *p outside of the loop and calling p = new Point inside the loop. Isn't there a better/nicer syntax for this?

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  • Iterator category

    - by Knowing me knowing you
    In code: //I know that to get this effect (being able to use it with std algorithms) I can inherit like I did in line below: class Iterator //: public std::iterator<std::bidirectional_iterator_tag,T> { private: T** itData_; public: //BUT I WOULD LIKE TO BE ABLE TO DO IT BY HAND AS WELL typedef std::bidirectional_iterator_tag iterator_category; typedef T* value_type;//SHOULD IT BE T AS value_type or T*? typedef std::ptrdiff_t difference_type; typedef T** pointer;//SHOULD IT BE T* AS pointer or T**? typedef T*& reference;//SHOULD IT BE T& AS reference or T*&? }; Basically what I'm asking is if I have my variable of type T** in iterator class is it right assumption that value type for this iterator will be T* and so on as I described in comments in code, right next to relevant lines. Thank you.

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  • Problem with pointers and getstring function

    - by volting
    I am trying to write a function to get a string from the uart1. Its for an embedded system so I don't want to use malloc. The pointer that is passed to the getstring function seems to point to garbage after the gets_e_uart1() is called. I don't use pointers too often so I'm sure it is something really stupid and trivial that Im doing wrong. Regards, V int main() { char *ptr = 0; while(1) { gets_e_uart1(ptr, 100); puts_uart1(ptr); } return 0; }*end main*/ //------------------------------------------------------------------------- //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char buffer_[SIZE_]; stringPtr_ = buffer_; int start_ = 0, end_ = SIZE_ - 1; char errorflag = 0; /*keep geting chars until newline char recieved*/ while((buffer_[start_++] = getchar_uart1())!= 0x0D) { putchar_uart1(buffer_[start_]);//echo it /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { start_ = 0; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(start_ == end_) { buffer_[0] = '\0'; errorflag = 1; } else { buffer_[start_++] = '\0'; } return errorflag; } Update: I decided to go with approach of passing a pointer an array to the function. This works nicely, thanks to everyone for the informative answers. Updated Code: //------------------------------------------------------------------------- //argument 1 should be a pointer to an array, //and the second argument should be the size of the array //gets a string and echos it //returns 0 if there is no error char getstring_e_uart1(char *stringPtr_, const int SIZE_) { char *startPtr_ = stringPtr_; char *endPtr_ = startPtr_ + (SIZE_ - 1); char errorflag = 0; /*keep geting chars until newline char recieved*/ while((*stringPtr_ = getchar_uart1())!= 0x0D) { putchar_uart1(*stringPtr_);//echo it stringPtr_++; /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; errorflag = 1; } } putchar_uart1('\n'); putchar_uart1('\r'); /*check for end of buffer wraparound if neccesary*/ if(stringPtr_ == endPtr_) { stringPtr_ = startPtr_; *stringPtr_ = '\0'; errorflag = 1; } else { *stringPtr_ = '\0'; } return errorflag; }

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  • Unmanaged C++ instantiation question

    - by Jim Jones
    Want to verify that my understanding of how this works. Have an unmanaged C++ Class with one public instance variable: char* character_encoding; and whose only constructor is defined as: TF_StringList(const char* encoding = "cp_1252"); when I use this class in either managed or unmanaged C++, the first thing I do is declare a pointer to an object of this class: const TF_StringList * categories; Then later I instantiate it: categories = new TF_StringList(); this gives me a pointer to an object of type TF_StringList whose variable character_encoding is set to "cp_1252"; So, is all that logic valid? Jim

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  • Bad allocation exceptions in C++

    - by me1982
    Hello, In a school project of mine I was requested to create a program not using STL. In the program I use alot of Pointer* = new Something; if (Pointer == NULL) throw AllocationError(); My question is about allocation errors: 1. is there an autamtic exception thrown by new when allocation fails? 2. if so how can I catch it if I'm not using STL (#include "exception.h) 3. is using the NULL testing enugh? thank you. I'm using eclipseCDT(C++) with MinGW on windows 7.

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  • Somewhat newb question about assy and the heap.

    - by Eric M
    Ultimately I am just trying to figure out how to dynamically allocate heap memory from within assembly. If I call Linux sbrk() from assembly code, can I use the address returned as I would use an address of a statically (ie in the .data section of my program listing) declared chunk of memory? I know Linux uses the hardware MMU if present, so I am not sure if what sbrk returns is a 'raw' pointer to real RAM, or is it a cooked pointer to RAM that may be modified by Linux's VM system? I read this: How are sbrk/brk implemented in Linux?. I suspect I can not use the return value from sbrk() without worry: the MMU fault on access-non-allocated-address must cause the VM to alter the real location in RAM being addressed. Thus assy, not linked against libc or what-have-you, would not know the address has changed. Does this make sense, or am I out to lunch?

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  • Best Practice for CouchDB Document Versioning

    - by Groundwater
    Following my question here I am exmploring ideas for a generic approach to document versioning in CouchDB. While I imagine there may be no canonical approach, I had the following idea and am looking for feedback. I would like to maintain readable document ids as much as possible, so a document existing at /document1 would contain a pointer document to all existing versions on the system. The actual revision documents would be at something like /document1/308ef032a3801a where 308ef032a3801a is some random number or hash. Example The pointer document { "_id" : "document1", "versions" : [ "document1/308ef032a3801a" ] } The version document { "_id" : "document1/308ef032a3801a", ... actual content }

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  • Why is comparing against "end()" iterator legal?

    - by sharptooth
    According to C++ standard (3.7.3.2/4) using (not only dereferencing, but also copying, casting, whatever else) an invalid pointer is undefined behavior (in case of doubt also see this question). Now the typical code to traverse an STL containter looks like this: std::vector<int> toTraverse; //populate the vector for( std::vector<int>::iterator it = toTraverse.begin(); it != toTraverse.end(); ++it ) { //process( *it ); } std::vector::end() is an iterator onto the hypothetic element beyond the last element of the containter. There's no element there, therefore using a pointer through that iterator is undefined behavior. Now how does the != end() work then? I mean in order to do the comparison an iterator needs to be constructed wrapping an invalid address and then that invalid address will have to be used in a comparison which again is undefined behavior. Is such comparison legal and why?

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  • template typename question

    - by stephenteh
    Hi, I have a problem with template and wondering is there a possible way to achieve what I wanted to do. Here is my question. template <typename T> class A { public: typedef T* pointer; typedef const pointer const_pointer; A() {} template <typename D> A(const D& d) { // how can I store the D type // so I can refer it later on // outside of this function } };

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