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Q&A

Posts tagged c++

3 child tags

Use this tag for questions concerning the use of the C++ programming language and for questions containing code in the C++ language. Avoid using it together with the C tag unless your question is explicitly about code compatibility or differences between C++ and C.

Unless the question explicitly mentions which version of the C++ standard that is uses, the current active version of ISO 14882 is assumed (C++17).

When applicable, always include information about which compiler and target system you are using.

This tag doesn't have a detailed wiki yet.

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Q&A How to write a macro that discards the const qualifier, for any type?

How to write a macro that discards the const qualifier, for any type? I hope some combination of typeof and a cast will do, but haven't found the combination. I tried this, without luck: #define...

2 answers  ·  posted 6mo ago by alx‭  ·  last activity 30d ago by alx‭

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Q&A Any testimonials for any C++ units of measure library?

The question is about libraries that extend the data type system to ensure physically realistic computations. Think std::chrono but for distance and mass and other things as well as for time. Inste...

1 answer  ·  posted 2mo ago by Fred Wamsley‭  ·  last activity 1mo ago by Ben‭

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Q&A What should I read if I knew C++ twenty years ago? [closed]

For someone who was familiar with C++ in the past and is coming back to it after a long break, what are some useful books that won't waste time with basics but will cover the new features of the mo...

0 answers  ·  posted 3mo ago by Fred Wamsley‭  ·  edited 3mo ago by Alexei‭

Question c++
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Q&A Is there any benefit to using new?

I've heard that in modern C++, smart pointers are preferred to raw pointers for ownership (the so-called RAII principle, as I understand it). This makes sense, and since then I've always used them...

1 answer  ·  posted 3mo ago by Moshi‭  ·  last activity 3mo ago by InfiniteDissent‭

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Q&A Do you need to use std::move to store a parameter passed by value?

If you have a class which needs to store a construction parameter internally, and you want to take advantage of move semantics, I understand that the parameter should be passed by value: class Foo...

1 answer  ·  posted 5mo ago by InfiniteDissent‭  ·  last activity 5mo ago by Dirk Herrmann‭

Question c++ reference
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Q&A Why can't a derived class add a const qualifier to a method?

Say we have an abstract class Foo declared as so: class Foo { public: virtual void test() = 0; }; Let's say that we make a derived concrete class FooDerived, and decide to mark it's ve...

2 answers  ·  posted 7mo ago by Moshi‭  ·  last activity 7mo ago by Dirk Herrmann‭

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Q&A How should one match a specialized version of a variant?

Let's say I have a variant that can hold a bunch of different types of values (say I got them from parsing a JSON or similar). using Value = std::variant&lt;std::monostate, int, double, std::strin...

0 answers  ·  posted 7mo ago by Moshi‭  ·  edited 7mo ago by Moshi‭

Question c++ variant
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Q&A C++ exit code -1073740940 [closed]

What means the exit code -1073740940 in C++?

2 answers  ·  posted 9mo ago by always_improve‭  ·  closed 9mo ago by Alexei‭

Question c++ exit-code
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Q&A What advantages does Agner Fog's VCL have over OpenMP?

Agner Fog has this C++ Vector Class Library, which is ... useful for improving code performance where speed is critical and where the compiler is unable to vectorize the code automatically in an...

1 answer  ·  posted 10mo ago by anatolyg‭  ·  edited 10mo ago by Alexei‭

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Q&A How to manage CPU capabilities of Jenkins nodes?

We use Jenkins Pipeline to build and test some C++ software. The pipeline script runs the tests on 10 different nodes in a parallel way in order to save time. All of these nodes are real (not virtu...

1 answer  ·  posted 11mo ago by anatolyg‭  ·  last activity 11mo ago by bta‭

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Q&A How kill a child process without read() hanging in the parent process?

There is an external program I'm calling from within my C/C++ program, by using fork() and execl(), and redirecting the stdio with dup2() to be able to read the output from the external program. I...

1 answer  ·  posted 1y ago by sktpin‭  ·  edited 1y ago by Lundin‭

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Q&A How to plot in C++?

I was trying to plot using following lines in C++. #include "koolplot.h" int main() { plotdata x(-6.0, 6.0); plotdata y = sin(x) + x/5; plot(x, y); return 0; } When I was...

0 answers  ·  posted 1y ago by Anonymous‭

Question c++ plot
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Q&A How allocated memory is calculated?

int arr[] = {10,123,14,14,15,16}; cout&lt;&lt;sizeof(arr)/sizeof(arr[0]); I was reading the article. When sizeof() is used with the data types such as int, float, char… etc it simply ret...

1 answer  ·  posted 1y ago by Anonymous‭  ·  last activity 1y ago by Canina‭

Question c++ memory
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Q&A What might happen if I ignore warning?

#include &lt;iostream&gt; using namespace std; int linearSearch(int array[], int n, int key){ for(int i=0;i&lt;=n;i++){ if(array[i]==key){ return i; } } } int main() { int ...

2 answers  ·  posted 1y ago by Anonymous‭  ·  last activity 1y ago by Lundin‭

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Q&A Print value from constructor

#include&lt;iostream&gt; using namespace std; class Book{ public: string title; string author; int pages; Book(string aTitle, string aAuthor, int aPages){ aTitle = title; ...

1 answer  ·  posted 1y ago by deleted user  ·  edited 1y ago by Alexei‭

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Q&A Tools for debugging coredumps

For debugging running programs I often use whatever is integrated with the IDE I am using. QtDeveloper right now, but also used Eclipse, Netbeans and others. Most of them just use gdb under the hoo...

0 answers  ·  posted 1y ago by Estela‭  ·  edited 1y ago by Estela‭

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Q&A Write to same file from multiple threads

I want to write a text file from multiple threads. The file structure is line-oriented. This means writing of lines should be atomic. I am using Qt 5.15.2. Is it enough to protect a shared QTextSt...

2 answers  ·  posted 1y ago by Silicomancer‭  ·  last activity 1y ago by Ayxan Haqverdili‭

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Q&A Multiple catches with almost the same code.

I find myself often writing code like this. try { // code } catch( FailedReadException const &amp; ex) { file.close(); std::cerr &lt;&lt; "Read failure " &lt;&lt; ex.readFailure() &lt;&...

2 answers  ·  posted 1y ago by Estela‭  ·  edited 1y ago by Ayxan Haqverdili‭

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Q&A Is `uint8_t` always an alias for a character type if it exists?

Is uint8_t guaranteed to be a character type if it exists? Will using a uint8_t* to examine bytes of an object cause violation of the strict aliasing rule? Is the following legal code: #include &l...

1 answer  ·  posted 1y ago by Ayxan Haqverdili‭  ·  edited 1y ago by Lundin‭

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Q&A Is it correct to run code inside a method whose object has been destroyed?

Consider an object for which a method is invoked. Beyond certain point the method no longer accesses this at all. No read/writes of non-static members. No invocation of non-static methods. Is it ...

1 answer  ·  posted 2y ago by Estela‭  ·  last activity 2y ago by Hyperlynx‭

Question c++ multithreading
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Q&A Destroy std::mutex referenced but not owned by std::unique_lock?

Is it correct to destroy a mutex which is referenced but not owned by an unique_lock as in this code? { std::unique_ptr&lt;std::mutex&gt; mutex = std::make_unique&lt;std::mutex&gt;(); std::u...

1 answer  ·  posted 2y ago by Estela‭  ·  last activity 2y ago by Angew‭

Question c++
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Q&A Scheme for cross-platform warning control?

tl;dr I'd like to learn a compact, cross-compiler way of selectively suppressing compiler warnings. Consider the case where you really mean to make an exact floating-point comparison using ==, o...

1 answer  ·  posted 2y ago by dmckee‭  ·  last activity 2y ago by Someone‭

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Q&A Confusion about using std::async with class member function

So,I'm having a doubt when I call std:async() on a member function of a class. The book I'm reading says (emphasis mine) You can also pass a pointer to a member function to async(). In that case...

1 answer  ·  posted 2y ago by hamsasimon‭  ·  last activity 2y ago by Chris Jester-Young‭

Question c++ multithreading
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Q&A Pros and cons of various type_traits idioms

My work tasks have recently started requiring me to use the type_traits header to restrict the classes that may be used in template functions, methods, and classes. And while I used it for a long t...

1 answer  ·  posted 2y ago by dmckee‭  ·  edited 2y ago by Marc.2377‭

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Q&A When should I use wait() instead of get() when using C++ threads

I'm trying to understand the purpose of the wait() function in Class future&lt;&gt; for C++. At the moment I don't see any purpose for calling wait() instead of get(). What I have tried in code: i...

1 answer  ·  posted 2y ago by hamsasimon‭  ·  last activity 2y ago by Derek Elkins‭

Question c++ multithreading
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Q&A Static and thread_local initialization order

Is there any guarantee regarding initialization of static and thread_local objects? In example, is there any guarantee about the value printed by the following program? #include&lt;iostream&gt; s...

1 answer  ·  posted 2y ago by Estela‭  ·  edited 2y ago by Alexei‭

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Q&A Having trouble adding include directories

I'm trying to set up a simple test project, to unit test a change I'm working on. The change is to a file inside some existing project. I've tried to set up the includes as the original has it, but...

1 answer  ·  posted 2y ago by Hyperlynx‭  ·  last activity 2y ago by Hyperlynx‭

Question c++ cmake
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Q&A connect with SLOT/SIGNAL: QPushButton clicked signal not received by main window

I added a QPushButton to my ui file named pushButton, and manually connected it using connect. There are no errors or warnings emitted at any point in the compilation stage The button does show up...

1 answer  ·  posted 2y ago by jrh‭  ·  last activity 2y ago by jrh‭

Question c++ qt
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Q&A Generate SIGSEGV without undefined behaviour.

In order to test that coredumps are generated and that they contain useful information which can be retreived with gdb I need to generate a SIGSEGV. Or anything else which causes a coredump. The co...

1 answer  ·  posted 2y ago by Estela‭  ·  last activity 2y ago by Lundin‭

Question c++ linux gcc