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C std::memory_order_seq_cst example

std::memory_order_seq_cst provides sequential consistency guarantees, ensuring that all threads see a consistent order of operations and no reordering occurs. 1. In the write thread, data.store(42, std::memory_order_seq_cst) is executed first, ready.store(true, std::memory_order_seq_cst), and the two will not be reordered; 2. The read thread waits through while(!ready.load(std::memory_order_seq_cst)). Once ready is true, it is guaranteed to be able to read the value of data to be 42; 3.

Aug 04, 2025 am 12:32 AM

C pass array to function example

In C, array transfers need to be careful not to be passed directly by value. 1. You can receive and pass in size with pointers. 2. Pass a fixed-size array with references to retain size information. 3. It is recommended to use std::array combined with const reference to achieve safe and efficient delivery. 4. You can process native arrays of arbitrary size through template functions to implement generic operations. You should avoid declaring only int[] parameters without size information. New projects should be given priority to using std::array.

Aug 03, 2025 am 09:32 AM

C vector get last element

It is recommended to use the back() member function to get the last element of std::vector, provided that the vector is not empty; 2. You can access the vec[vec.size()-1] or a safe at() method through the subscript, which throws an exception when it is crossed; 3. You can also use iterator methods, such as *(vec.end()-1) or vec.rbegin()[0]; in summary, the most commonly used and efficient method is to call back(), but you must first check whether the vector is empty to avoid undefined behavior. This method is clear in semantics and good in performance, and is suitable for most scenarios.

Aug 03, 2025 am 09:24 AM

How to get started with OpenCV in C

Install OpenCV: Windows users recommend using vcpkg or precompiled libraries, Linux users use apt to install libopencv-dev, macOS users use Homebrew to install opencv; 2. Set up C project: You can compile and link OpenCV through the g command line, or use CMake to manage project construction; 3. Verify installation: Prepare test images and run the program that loads the image display to ensure that the image window pops up normally, and troubleshoot paths, links or DLL problems; 4. Learn basic operations: master core functions such as image reading and writing, video capture, matrix processing, drawing and color conversion, and further familiarize yourself with the API by running examples such as camera capture; installation is successful and able to

Aug 03, 2025 am 08:58 AM

c++ opencv

C std::jthread example (C 20)

std::jthread automatically joins during destruction to avoid resource leakage or crashes; ① Support automatic join, no need to call join or detach manually; ② Provide stop_token and request_stop to achieve collaborative interrupts; ③ Cleanup operations can be performed through stop_callback; ④ stop_token can be passed to other functions or threads for responding to stop requests; ⑤ Does not support detach to ensure safe waiting for threads; suitable for multi-threading scenarios under C 20 that require safe management and elegant termination, the C 20 standard must be enabled and pthread is linked.

Aug 03, 2025 am 08:52 AM

C++20

C mutex example

std::mutex is used to protect shared resources to prevent data competition. In the example, the automatic locking and unlocking of std::lock_guard is used to ensure multi-thread safety; 1. Using std::mutex and std::lock_guard can avoid the abnormal risks brought by manual management of locks; 2. Shared variables such as counters must be protected with mutex when modifying multi-threads; 3. RAII-style lock management is recommended to ensure exception safety; 4. Avoid deadlocks and multiple locks in a fixed order; 5. Any scenario of multi-thread access to shared resources should use mutex synchronization, and the final program correctly outputs Expected:10000 and Actual:10000.

Aug 03, 2025 am 08:43 AM

c++ mutex

C gRPC example

First install gRPC and Protobuf related tools; 2. Define the helloworld.proto file to declare services and messages; 3. Use protoc to generate four C code files: helloworld.pb.cc, helloworld.pb.h, helloworld.grpc.pb.cc, helloworld.grpc.pb.cc, helloworld.grpc.pb.h; 4. Implement the server.cpp, define the GreeterServiceImpl class to handle SayHello requests and start the gRPC server; 5. Implement the client.cpp, create the GreeterClient to call the remote Sa

Aug 03, 2025 am 08:36 AM

C set a bit example

To set a specific bit in C, use the bit or and left shift operators. The specific steps are: 1. Move 1 left n bits to generate a mask; 2. Perform bitwise or assignment of the original number and mask. For example number|=(1

Aug 03, 2025 am 08:29 AM

C double free error example

The doublefree error refers to multiple calls to delete or free on the same piece of dynamically allocated memory, resulting in undefined behavior, which usually causes program crashes; 2. Common reasons include that pointer sharing is not managed, not set to nullptr after release, and that the class does not correctly implement the copy constructor or assignment operator, resulting in shallow copy; 3. Avoiding methods include setting the pointer to nullptr after release, using smart pointers such as std::shared_ptr or std::unique_ptr, following three or five rules, and prioritizing the use of RAII containers such as std::vector and std::string; 4. In actual programming, repeated release of the same memory should be eliminated, and smart pointers are recommended.

Aug 03, 2025 am 07:49 AM

How to convert a string to an int in C

Use std::stoi() (C 11) to convert strings into integers, and try-catch is required to handle invalid parameters or out-of-bounds exceptions; 2. Use std::stringstream to safely convert and check the flow state, but need to combine eof() to detect trailing characters; 3. Use std::from_chars() (C 17) to have no exceptions and no memory allocation, the performance is best, and suitable for high-performance scenarios; when selecting methods, it should be decided based on C version and error handling requirements. Modern code recommends std::stoi to cooperate with exception handling, and std::from_chars is recommended for performance key scenarios.

Aug 03, 2025 am 07:46 AM

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C std::move example

The purpose of std::move is to convert the lvalue to an rvalue reference, thereby triggering the move semantics rather than copying. 1. In the vector example, std::move(source) makes dest obtain the source's resources through the move constructor, and the source is empty to avoid deep copy overhead. 2. In the custom class Person, the mobile constructor realizes resource transfer by taking over the pointer and juxtaposing the original pointer to nullptr, improving efficiency and preventing memory leakage. 3. After using std::move, the original object can still be destructed but should not be used again. Its status is valid but undefined. 4. Common uses include inserting large objects into containers, optimizing function return value (although often replaced by RVO), and transfer of member variables.

Aug 03, 2025 am 06:03 AM

C extern 'C' example

extern"C" is used to solve the linking problem when C calls C functions. 1. Use #ifdef__cplusplus to wrap extern"C" in the header file to ensure that the C compiler does not modify the name, and the C compiler can handle it normally; 2. The C implementation file is written in the standard C syntax, and the target file is compiled and generated; 3. The main C program contains the header file and calls the function. When compiling, use g to link the target files of C and C, and finally successfully call the C function and output the result. Therefore, as long as the extern "C" protection function declaration is used correctly, a mixed compilation and link between C and C can be achieved.

Aug 03, 2025 am 05:05 AM

How to link a static library in C using g

AstaticlibraryinC isanarchivefilewitha.aextensioncontainingcompiledobjectfiles.2.Compilesourcefilesintoobjectfilesusingg -candcreatethestaticlibrarywitharrcslibname.aobject_file.o.3.Linkthelibrarytoyourmainprogramusingg main.cpp-L.-lname-omain,ens

Aug 03, 2025 am 04:52 AM

Observer Pattern in C

Observer mode realizes decoupled communication between objects through the design of Subject and Observer in C. The specific steps are as follows: 1. Define the Observer interface and declare the update method; 2. Implement the Subject class to maintain the observer list and provide methods for adding, removing and notification; 3. Use smart pointers such as std::weak_ptr to avoid memory leaks and wild pointers; 4. Pay attention to circular references, thread safety and performance issues, and can be optimized through asynchronous or throttling mechanisms; 5. Apply to GUI, event systems and other scenarios, such as button clicks to trigger multiple listening operations.

Aug 03, 2025 am 04:20 AM

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