Recent questions tagged C++

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c++ - autotools syntax error with ax_check_compile_flag

I am using autotools for building my C++ application. In my configure.ac I have the following line: ... do I get this error? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Evaluating stream operator >> as boolean

The following code compiles in Visual Studio 2008 but fails in Visual Studio 2013 and later. std::string str("foo" ... an operator== break it? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What's the difference between input iterators and read-only forward iterators?

What's the difference between input iterators and read-only forward iterators? Because the latter are read-only, they ... not, am I right? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - class friend function inside a namespace

Im trying to define a class friend function outside the namespace like this: namespace A{ class window{ private: ... is declared a friend. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Can you add a toolbar to QDialog?

I'm working on a project that needs to call a modal window with a toolbar to do some work on some data ... can I make a QMainWindow modal? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Thread safety of ::new in C++11

I am certain that, in practice, use of ::new is thread-safe. My question is what part of the standard provides that ... safe (in C++11). Thanks! See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - FILETIME to __int64

What is the proper way to convert a FILETIME structure into __int64? Can you please tell me? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to use the <format> header

In a related question ("std::string formatting like sprintf") I learned about this awesome new C++20 header <format>. ... -o test -std=c++2a See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - std::map difference between index and insert calls

What is the difference between the index overloaded operator and the insert method call for std::map? ie: some_map["x"] = ... , int>("x", 500)); See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Gcc: force compiler to use unsigned char by default

Since the nature of a char in C++ is compiler-dependent when the unsigned qualifier is not present, is there ... to be compiled as unsigned? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why do I get cc1plus: error: unrecognized command line option "-arch"?

/usr/bin/make -f nbproject/Makefile-Debug.mk SUBPROJECTS= .build-conf /usr/bin/make -f nbproject/Makefile-Debug. ... { return (EXIT_SUCCESS); } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Vector of structs with const members?

Let's say I have #include <string> #include <vector> using namespace std; struct Student { const string name; int ... to each of them instead? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Develop using OpenGL 4.x on OSX Big Sur

According to Apple, OpenGL is no longer supported. However, it appears v4.1 of OpenGL was supported on many devices ... options am I left with? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How do i verify a string is valid double (even if it has a point in it)?

I have been up all night searching for a way to determine if my string value is a valid double and I haven't ... with a point gets rejected... See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Need to enable C++11 in Codeblocks

I need to enable C++11 in Codeblocks 16. Several tutorials explain that all one needs to do is select the "Have ... comes with it on Windows 7. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - g++ include all /usr/include recursively

I'm trying to compile a simple program, with #include <gtkmm.h> The path to gtkmm.h is /usr/include/gtkmm-2 ... is this not the default action? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Activating C++11 support in Clang

I've downloaded and built clang version 3.0 in order to play around a bit with C++11 features, however I ... VS command prompt all was well. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Get part of a char array

I feel like this is a really silly question, but I can't seem to find an answer anywhere! Is it possible to ... strings so I can use substr()? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What is type punning and what is the purpose of it?

Type punning A form of pointer aliasing where two pointers and refer to the same location in memory but represent that ... it or not use it? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why does g++ still require -latomic

In 29.5 Atomic types of the C++ Standard November 2014 working draft it states: There is a generic class ... by the compiler maintainers, yet? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Comparison with string literal results in unspecified behaviour?

I am having a problem with the program I am trying to code. It's just a Windows console program and I am ... which is what it needs to work. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - When is static cast safe when you are using multiple inheritance?

I found myself in a situation where I know what type something is. The Type is one of three (or more) levels of inheritance. ... b << " " <<c; } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Ignore 'E' when reading double with sscanf

I have input such as "(50.1003781N, 14.3925125E)" .These are latitude and longitude. I want to parse this ... Is there way to disable this? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Is there a g++ equivalent to Visual Studio's __declspec(novtable)?

Is there a g++ equivalent to Visual Studio's __declspec(novtable) argument? Basically, in a pure virtual base ... Also see my related question. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How do I force my std::map to deallocate memory used?

I'm using a std::map, and I can't seem to free the memory back to the OS. It looks like, int main() ... The flush has to appear after the clear. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Error building Boost 1.49.0 with GCC 4.7.0

I'm trying to build Boost 1.49.0 using GCC 4.7.0 (MinGW). I keep getting the following error message ... ideas why I am getting this error? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - CMake & QT5 - QT5_WRAP_UI not generating ui header files

I have a simple CMakeLists.txt that looks like this: CMAKE_MINIMUM_REQUIRED(VERSION 2.8) PROJECT(calculator) FIND_PACKAGE( ... * [all] Error 2 See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Can we rely on op== to binary-compare floating-point values?

We all know (right?!) that one should not compare floating-point values by testing for equality (operator==). But ... = to function in this way? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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