Recent questions tagged C++

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c++ - Can the use of C++11's 'auto' improve performance?

I can see why the auto type in C++11 improves correctness and maintainability. I've read that it can also ... ? Can anyone give an example? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - A fast method to round a double to a 32-bit int explained

When reading Lua's source code, I noticed that Lua uses a macro to round double values to 32-bit int values. ... precision numbers: 1.5? ?223. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Spinlock versus Semaphore

What are the basic differences between a semaphore & spin-lock? When would we use a semaphore over a spin-lock? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to create a shared library with cmake?

I have written a library that I used to compile using a self-written Makefile, but now I want to switch to ... can use this as an example. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What happens when a computer program runs?

I know the general theory but I can't fit in the details. I know that a program resides in the secondary ... to the stack, to the registers? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - If always returns true

I'm just experimenting a bit with C++ but I can't figure out why both if-statements return true: #include < ... t know any further. Please help! See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - I/O in concurrent program

I'm working on a concurrent program; it has two threads, one of which listens messages from a server and the ... other stuff. Thanks in advance See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Reference a temporary in msvc

Why does this compile on MS Visual C++? struct myClass{}; void func(myClass& arg){} void main() { func( myClass ... ) + myClass()) for example.. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Calling a function in main

I'm just learning C++ and I have a little code here: using namespace std; int main() { cout<<"This ... but doesn't execute the moon_g function. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Unoptimized clang++ code generates unneeded "movl $0, -4(%rbp)" in a trivial main()

I created a minimal C++ program: int main() { return 1234; } and compiled it with clang++5.0 with ... t correspond to anything in the source? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Libpng, Palette png with alpha or not?

How to know if palette png is with alpha or not? I get information about the image png_get_IHDR After that i ... has alpha channel or not. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to truncate a file while it is open with fstream

I know it is possible to truncate a file with std::fstream fs(mypath, std::fstream::out | std::fstream: ... whole operation is atomic). Anyone? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Is std::abs(0u) ill-formed?

Given the following program: #include <cmath> int main() { std::abs(0u) ; } gcc and clang disagree on ... : Template version of std::abs. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Implementing 64 bit atomic counter with 32 bit atomics

I would like to cobble together a uint64 atomic counter from atomic uint32s. The counter has a single ... auto acquire = memory_order_release; See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Why do I get _CrtIsValidHeapPointer(block) and/or is_block_type_valid(header->_block_use) assertions?

When I run my with VisualStudio compiled programs in debug-mode, sometimes I get Debug assertion failed! Expression ... origin of such problems? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What is "for (x : y)"?

So i was looking around on the interwebs about threads and i came to a blog/tutorial thing about threads but ... be blind when searching for one See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How does __builtin___clear_cache work?

Going through the gcc documentation, I stumbled into the builtin function __builtin___clear_cache. - Built-in Function: void ... and end to use? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Can we rely on the reduce-capacity trick?

Is it actually guaranteed anywhere that the following reduce-capacity trick will "work"? int main() { std::string ... making this kind of moot.) See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Is reading an indeterminate value undefined behavior?

The question arose in the comments of an answer to the question Is C/C++ bool type always guaranteed to ... 2007/02/c-indeterminate-value.html See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Class vs Struct for data only?

Is there any advantage over using a class over a struct in cases such as these? (note: it will only hold ... a struct instead of a class? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - rand() generating the same number – even with srand(time(NULL)) in my main!

So, I'm trying to create a random vector (think geometry, not an expandable array), and every time I call ... 8? Am I seeding incorrectly? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - What is going on with bitwise operators and integer promotion?

I have a simple program. Notice that I use an unsigned fixed-width integer 1 byte in size. #include <cstdint> ... to the great answers below. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Using `std::function<void(...)>` to call non-void function

A while ago I used std::function pretty much like this: std::function<void(int)> func = [](int i) -> int { ... once a call to func() is made. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - The precision of std::to_string(double)

Is there any way to set the precision of the result when converting a double to string using std::to_string()? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Are pointer variables just integers with some operators or are they "symbolic"?

EDIT: The original word choice was confusing. The term "symbolic" is much better than the original ("mystical"). ... I was wrong to borrow it. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Modifying a char *const string

I know that const char * is a pointer to a const char, while char *const is a constant pointer to a char ... string pointed to by t not allowed? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - How to rearrange a string equation?

I am required to develop a program to solve linear equations. The programs reads first an integer n which is ... should I approach the problem? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c++ - Code runs perfect in g++ but not in Xcode - Cannot find File

I have created a text file with content. It is located in the same folder as the cpp files. And I have confirmed ... to open file"; return 0; } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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