java,c++,windows,multithreading , Is there an equivalent of Java 'volatile' in C++?


Is there an equivalent of Java 'volatile' in C++?

Question:

Tag: java,c++,windows,multithreading

In Java, sometimes when accessing the same variable from different threads, each thread will create its own copy of the variable, and so if I set the value of the variable in one thread to 10 and then I tried to read the value of this variable from another thread, I will not get 10 (because the second thread is reading from another copy of the variable!).

To fix this problem in Java, all I had to do is to use the keyword volatile, for example:

volatile int i = 123;

Does this problem also exists in C++? If so, how can I fix it?

Note: I am using Visual C++ 2010.


Answer:

Yes, the same problem exists in C++. But since C already introduce the keyword volatile with a different meaning (not related to threads), and C++ used they keyword in the same way, you can't use volatile in C++ like you can in Java.

Instead, you're probably better off using std::atomic<T> (or boost::). It's not always the most efficient alternative, but it's simple. If this turns out to be a bottleneck, you can relax the std::memory_order used by std::atomic.

Having said that about standard C++, MSVC++ as an extension does guarantee that multiple threads can access a shared volatile variable. IIRC, all threads will eventually see the same value, and no threads will travel back in time. (That is to say, if 0 and 1 are written to a variable sequentially, no thread will ever see the sequence 1,0)


Related:


How can I access the members of a subclass from a superclass with a different constructor?


c++,inheritance,constructor,subclass,superclass
I have the following class and typedef: class Object { protected: long int id; public: Object(void); ~Object(void) {}; long int get_id(void); }; typedef map<string, Object> obj_map; And then I have its child: class Image: public Object { private: path full_path; int x; int y; img image; public: Image(path p, int...

type conversion if flex


java,actionscript-3,flex
I am using Flerry as Java-Flex bridge for my Flex Desktop Application. How to convert List in Java to ArrayCollection in Flex Flex Code:- [Bindable]public var screenList:ArrayCollection; <flerry:NativeObject id="windowControllerObj" source="ls.window.EnumAllWindowNames" singleton="true" fault="windowControllerObj_faultHandler(event)"> <flerry:NativeMethod id="getWindowNames" name="getAllWindowNames" result="windowControllerObj_resultHandler(event)" fault="getWindowNames_faultHandler(event)"/>...

.cpp:23: error: cannot convert ‘std::string’ to ‘const char*’ for argument ‘1’ to ‘int atoi(const char*)’


c++,string
Here a basic code I'm trying to run But I'm having trouble with stoi (it's c++) I keep getting error: ‘stoi’ was not declared in this scope I tried atoi and strtol with this error .cpp:23: error: cannot convert ‘std::string’ to ‘const char*’ for argument ‘1’ to ‘int atoi(const char*)’...

Android set clickable text to go one fragment to another fragment


java,android,android-fragments,spannablestring
I need to do something like this. Suppose I have 2 fragments A and B.There is a text which can be clickable in fragment A and when user click this text , he can go to fragment B. This example helped me to do it but I think it does...

Get current latitude and longitude android


java,android,gps,geolocation,location
Requirement: 1.Sometimes(not everytime) I am getting latitude and longitude 0.0. 2.I want to know how to get the location update after user has enabled the gps from the settings. Here is my code public class GPSTracker extends Service implements LocationListener { private final Context mContext; // flag for GPS status...

dispatch response packet according to packet sequence id


c++,boost,boost-asio
I have a third-part server, and I'm writing a dll interface for it, my clients use my dll to communicate with the server. The protocol uses a long tcp connection, all traffic goes from this tcp connection. There could be sending/receiving multiple packets at the same time, like a send_msg...

Using world coordinates


java,libgdx
I am currently using pixels as units for placing objects within my world, however this can get tedious because I only ever place objects every 16 pixels. For example, I would like to be able to place an object at position 2 and have the object rendered at the pixel...

pointer to pointer dynamic array in C++


c++,arrays,pointers
I've been having bad luck with dynamic pointers when I want to close it. why the application wrote to memory after end of heap buffer? how can I close my array? int main() { . . int **W; W = new int* [n]; for (int i=1; i <= n; i++)...

Method returning std::vector>


c++
As a continuation of a: Thread, I came across a problem with writing a method of a class which returns: std::vector<std::unique_ptr<Object>> I get compiler errors when such a return type is written. There is some problem with delete operand or something ... Generally, I've wanted to write a method which...

BitmapFont class does not have getBound(String) method


java,android,libgdx
Previously I used getBound method for BitmapFont class in libgdx, but now, I am unable to use it. I cannot find the changes in latest version. Any help is appreciated. Thank you...

Can I install 2 or more Android SDK when using Eclipse


java,android,eclipse,sdk,versions
I am new to android developments. I am setting up my android development environment using Eclipse. I have a test smart phone with Android version 4.2.2. The automatic installation installed the latest Android SDK version, which is 5.1.1. My questions are: 1. Do I have to install the SDK version...

Mysterious claim of a missing { in eclipse


java,eclipse
I have a case of a mysterious missing curly brace that I don't see any use for. Eclipse says, "Syntax error on token ";", { expected after this token". Either I am missing something very silly or there is something new I have to learn about Java. This is the...

How to do custom rounding of numbers in Java?


java,rounding
Suppose I want to round numbers that have mantissa greater than 0.3 'up' and those below 'down'. How can I do it in Java? The only thing that came to my mind was Math.round(), but I can't seem to make it follow a certain rule....

SOAP Client, Following an example


java,soap,saaj
I need to consume a SOAP Server named "Mouser" for my company. However I have a problem when I try to send a message. The documentation of my request is : POST /service/searchapi.asmx HTTP/1.1 Host: www.mouser.fr Content-Type: application/soap+xml; charset=utf-8 Content-Length: length <?xml version="1.0" encoding="utf-8"?> <soap12:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap12="http://www.w3.org/2003/05/soap-envelope"> <soap12:Header> <MouserHeader...

Finding embeded xpaths in a String


java,regex
I have a string where I have the user should be able to specify xpaths that will be evaluated at runtime. I was thinking about having a the following way to specify it. String = "Hi my name is (/message/user) how can i help you with (/message/message) "; How can...

Selenium catch popup on close browser


java,selenium,browser
I'm trying to test that when I close my window a popup shows with a warning message. I've tried both driver.close() and driver.quit() after making sure I'm on the proper window but this just terminates the process since my popup doesn't show. I could test it by using the awt...

Android String if-statement


java,android,string
I have a if-statement in the start of my app if (ready.equals("yes")){ ... } and later on my code I have ready="yes"; but the if statement is never called, why? The ready="yes"; is called from a background thread, is that why? public void DownloadFromUrl(final String fileName) { //this is the...

why java API prevents us to call add and remove together?


java,list,collections,listiterator
As per Java API- IllegalStateException - if neither next nor previous have been called, or remove or add have been called after the last call to next or previous remove()- Removes from the list the last element that was returned by next() or previous() (optional operation). This call can only...

PropertyNotFoundException in jsp


java,jsp
Am getting this error in my application javax.el.PropertyNotFoundException: Property 'survey_id' not found on type com.moh.forms.MOH731 javax.el.BeanELResolver$BeanProperties.get(BeanELResolver.java:229) javax.el.BeanELResolver$BeanProperties.access$400(BeanELResolver.java:206) javax.el.BeanELResolver.property(BeanELResolver.java:317) javax.el.BeanELResolver.getValue(BeanELResolver.java:85) This is my MOH731.java @Id @GeneratedValue(strategy = GenerationType.AUTO) private int survey_id; public MOH731 (int survey_id, String uname)...

Unfortunately, (My app) has stopped. Eclipse Android [duplicate]


java,android,eclipse,adt
This question already has an answer here: What is a Null Pointer Exception, and how do I fix it? 12 answers I'm a beginner in android developing and I'm trying to build a simple app but I'm getting this error in the emulator.(Unfortunately,(App) has unexpectedly stopped). LogCat http://i.stack.imgur.com/VZhuL.png package...

Get element starting with letter from List


java,android,list,indexof
I have a list and I want to get the position of the string which starts with specific letter. I am trying this code, but it isn't working. List<String> sp = Arrays.asList(splited); int i2 = sp.indexOf("^w.*$"); ...

Form submit portlet with Spring MVC


java,jsp,spring-mvc,liferay,portlet
I'm trying to achieve a Liferay portlet of submit form using spring MVC. The model: package com.model; public class Person { String firstName; String middleName; public String getFirstName() { return this.firstName; } public String getMiddleName() { return this.middleName; } public void setFirstName(String firstName) { this.firstName=firstName; } public void setMiddleName(String middleName)...

Javadoc: Do parameter and return need an explicit type description


java,types,javadoc
When Javadoc'ing, I don't know whether you should explicitly say whether the parameters are of type String or int. For example /** * This method does something * @param foo an object of type Foo * @param abc the number of doors, of type int * @return the number of...

Same function with and without template


c++,c++11
I am trying to understand a piece of code of C++11. A class contains 2 functions as shown below: class abc { public: void integerA(int x); template<typename typ> void integerA(typ x); }; I am unable to understand benefit of declaring 2 same functions. Why not declare only one template function?...

Implicit use of initializer_list


c++,c++11,initializer-list
§[dcl.init.list] 8.5.4/2: The template std::initializer_list is not predefined; if the header <initializer_list> is not included prior to a use of std::initializer_list — even an implicit use in which the type is not named (7.1.6.4) — the program is ill-formed. Does that mean this program is ill-formed? #include <vector> int main()...

Get network interfaces on remote machine


java,network-programming
I know in java we can do NetworkInterface.getNetworkInterfaces() to get all available network interfaces on local machine. Can we do similar thing where I can pass host name to get the NICs(with IPs) which are up and running?

App Not Downloading Newest Version Of File [Java]


java,caching,download
Okay, I've been trying to figure this out for a few hours and it's starting to kill me. I wrote a primitive version checker for an app I work on every once and awhile. It's just a simple for fun project. The version checker has been a pain though. It...

Get document on some condition in elastic search java API


java,elasticsearch,elasticsearch-plugin
As I know we can parse document in elastic search, And when we search for a keyword, It will return the document using this code of java API:- org.elasticsearch.action.search.SearchResponse searchHits = node.client() .prepareSearch() .setIndices("indices") .setQuery(qb) .setFrom(0).setSize(1000) .addHighlightedField("file.filename") .addHighlightedField("content") .addHighlightedField("meta.title") .setHighlighterPreTags("<span class='badge badge-info'>") .setHighlighterPostTags("</span>") .addFields("*", "_source")...

Getting particular view from expandable listview


java,android,listview,android-fragments,expandablelistview
In my list view I have an textview in expandable group and I want to open the dialog when textview is clicked to fill the information through edittext and update textview. Problem: how could I get the groupview textview item in my fragment oncreateview() method....

viewResolver with more folders inside of WEB-INF/jsp is not working in spring


java,spring,jsp,spring-mvc
<bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView" /> <!-- avoid '???' --> <property name="prefix" value="/WEB-INF/jsp/" /> <property name="suffix" value=".jsp"/> </bean> if i create other subfolders under jsp , for instance /WEB-INF/jsp/reports , /WEB-INF/jsp/insertions how should i configure now the viewResolver to can resolve these new sub folders??...

custom arraylist get distinct


java,android
is there any way to get the distinct values of a custom arraylist? public class mystatistic extends BaseActivity { public String objectid; public String playerid; public String playername; public String enemyid; public String enemyname; public String question; public mystatistik(String objectid, String playerid, String playername, String enemyid, String enemyname, String question)...

How to block writes to standard output in java (System.out.println())


java,logging,stdout
In Java, how to block code from writing to system out? My app calls a 3rd party library that spams logs by issuing numerous System.out.println() calls. I don't have legal rights to decompile and patch the library. I'm running Websphere 8.5.x Considered using System.setOut(PrintStream out), but that will effect the...

Add more features to stack container


c++,visual-c++,stl
I am using default features(push, pop, top, empty, size) of stack container of STL. If I want to add more features like access an element from middle of stack. How could I do this? Thanks...

Android Implicit Intent for Viewing a Video File


java,android,android-intent,uri,avd
In my Android app, I have a button that when clicked, launches the external application of my choice to play a video (I gather that this is called an "implicit intent"). Here is the relevant Java code from my onCreate method. Button button = (Button) findViewById(R.id.button); button.setOnClickListener ( new Button.OnClickListener()...

error: cannot find symbol class AsyncCallWS Android


java,android,web-services
I'm trying to rewrite the application in this, in Android Studio link, which is written in Eclipse. There are two problems, first problem is there is this line in the project : import com.example.webserviceactivity.R; I couldn't write this one on Android Studio. The second problem is, in this part of...

Reading and modifying the text from the text file in Java


java
I am have a project that need to modify some text in the text file. Like BB,BO,BR,BZ,CL,VE-BR I need make it become BB,BO,BZ,CL,VE. and HU, LT, LV, UA, PT-PT/AR become HU, LT, LV, UA,/AR. I have tried to type some code, however the code fail to loop and also,in this...

Java dice roll with unexpected random number


java,if-statement
I've written a simple Java program to display the results of 20 dice rolls on the console. The results I'm getting are listed below: 3 1 [email protected] 1 5 4 1 [email protected] 1 [email protected] [email protected] 1 6 [email protected] 1 [email protected] [email protected] 1 2 3 3 When I ran it for...

how to call Java method which returns any List from R Language? [on hold]


java,r,rjava
How to call java method which returns list from R Language.

Get the value of the last inserted record


java,jdbc
I am trying to get the stop_name of the last inserted row in the table with preparedStatement. How can I get the last inserted one? I appreciate any help. behavoiur table: CREATE TABLE IF NOT EXISTS behaviour( behaviour_id INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY, mac VARCHAR(30) NOT NULL, stop_name VARCHAR(30)...

Marshal struct in struct from c# to c++


c#,c++,marshalling
I have the following structures in C# and C++. C++: struct TestA { char* iu; }; struct TestB { int cycle1; int cycle2; }; struct MainStruct { TestA test; TestB test2; }; C#: [StructLayout(LayoutKind.Sequential, CharSet=CharSet.Ansi, Pack = 1)] internal struct TestA { [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 36)] private string iu; public...

Logging operations in lightadmin


java,spring,logging,lightadmin
I have a Java web application which use Spring and Hibernate and I plan to use lightadmin to provide an administration interface. However, I found very little information about the logging part of lightadmin : if I have such an adminsitration interface, I would like that any operation made to...

How can implement long running process in spring hibernate?


java,spring,hibernate
as we know the struts interceptor execute and wait will take care of long running process by not getting the request to timeout and destroy it sends wait and at last the desired response i want to implement the same for long running process in spring and hibernate. Thanks....

Why are shaders and programs stored as integers in OpenGL?


c++,opengl,opengl-es,integer,shader
I'm following the "OpenGL Superbible" book and I can't help but notice that when we create a shader and create the program that we attach the shaders to, we store them as GLuint which are unsigned integers. Why are they stored as numbers? What does the value of the number...

How to call MySQL view in Struts2 or Hibernate


java,mysql,hibernate,java-ee,struts2
I have a view in MySQL database CREATE VIEW CustInfo AS SELECT a.custName, a.custMobile, b.profession, b.companyName, b.annualIncome FROM customer a INNER JOIN cust_proffessional_info b ON a.cust_id=b.cust_id Is there any way that i can call this view using Struts2 or in Hibernate. I have tried to search it but could not...

Join files using Apache Spark / Spark SQL


java,apache-spark,apache-spark-sql
I am trying to use Apache Spark for comparing two different files based on some common field, and get the values from both files and write it as output file. I am using Spark SQL for joining both files (after storing the RDD as table). Is this the correct approach?...

Undefined behaviour or may be something with memset


c++,undefined-behavior
I was trying to save the binary equivalent of a 32 bit number in an array A. For testing my showbits() function , I choosed 8,9 when I came across this thing: I am facing an unreasonable thing in my code when I am placing memset in the function showbits(),I...

How can I convert an int to a string in C++11 without using to_string or stoi?


c++,string,c++11,gcc
I know it sounds stupid, but I'm using MinGW32 on Windows7, and "to_string was not declared in this scope." It's an actual GCC Bug, and I've followed these instructions and they did not work. So, how can I convert an int to a string in C++11 without using to_string or...

Interpreting hex dump of java class file


java,class,hex
I understand the structure of a java .class file, but when I want to interpret the raw hex data I get a bit lost. This is a hex dump of a class file, excluding the header and constant pool. I understand the header to be the magic number, minor_version and...

Translating a character array into a integer string in C++


c++,arrays,string
I was trying to achieve translating a character array into a integer string and corresponding character to their alphabetical order. For instance: A(a) = 0 , Z(z) = 25. string key_char = argv[1]; string key_num; for (int i = 0; i < key_char.length(); i++){ if (isalpha(key_char[i])){ if (islower(key_char[i])){ key_num[i] =...

Java Scanner not reading newLine after wrong input in datatype verification while loop


java,while-loop,java.util.scanner
I've looked at similar questions and tried to follow the answers that solved the issues that others have had but putting the sc.next() or sc.nextLine() after the while loop causes it to go into an infinite loop. The problem is if a user enters incorrect input (nothing or a number)...