Why Does SelectSingleNode Return Null When Dealing with XML Namespaces?

If it is iterating when deleting an element, you must avoid using a failed iterator. ①The correct way is to use it=vec.erase(it), and use the valid iterator returned by erase to continue traversing; ② The recommended "erase-remove" idiom for batch deletion: vec.erase(std::remove_if(vec.begin(),vec.end(), condition), vec.end()), which is safe and efficient; ③ You can use a reverse iterator to delete from back to front, the logic is clear, but you need to pay attention to the condition direction. Conclusion: Always update the iterator with the erase return value, prohibiting operations on the failed iterator, otherwise undefined behavior will result.

Use std::source_location::current() as the default parameter to automatically capture the file name, line number and function name of the call point; 2. You can simplify log calls through macros such as #defineLOG(msg)log(msg,std::source_location::current()); 3. You can expand the log content with log level, timestamp and other information; 4. To optimize performance, function names can be omitted or location information can be disabled in the release version; 5. Column() and other details are rarely used, but are available. Using std::source_location can significantly improve the debugging value of logs with extremely low overhead without manually passing in FIL

TheautokeywordinC deducesthetypeofavariablefromitsinitializer,makingcodecleanerandmoremaintainable.1.Itreducesverbosity,especiallywithcomplextypeslikeiterators.2.Itenhancesmaintainabilitybyautomaticallyadaptingtotypechanges.3.Itisnecessaryforunnamed

memory_order_relaxed is suitable for scenarios where only atomicity is required without synchronization or order guarantee, such as counters, statistics, etc. 1. When using memory_order_relaxed, operations can be rearranged by the compiler or CPU as long as the single-threaded data dependency is not destroyed. 2. In the example, multiple threads increment the atomic counter, because they only care about the final value and the operation is consistent, the relaxed memory order is safe and efficient. 3. Fetch_add and load do not provide synchronization or sequential constraints when using relaxed. 4. In the error example, the producer-consumer synchronization is implemented using relaxed, which may cause the consumer to read unupdated data values because there is no order guarantee. 5. The correct way is

Singleton pattern ensures that a class has only one instance and provides global access points. C 11 recommends using local static variables to implement thread-safe lazy loading singletons. 1. Use thread-safe initialization and delayed construction of static variables in the function; 2. Delete copy construction and assignment operations to prevent copying; 3. Privatization of constructs and destructors ensures that external cannot be created or destroyed directly; 4. Static variables are automatically destructed when the program exits, without manually managing resources. This writing method is concise and reliable, suitable for loggers, configuration management, database connection pooling and other scenarios. It is the preferred singleton implementation method under C 11 and above standards.

Use the seekg and tellg methods of std::ifstream to obtain file size across platforms. By opening a binary file and positioning it to the end, use tellg() to return the number of bytes; 2. It is recommended to use std::filesystem::file_size for C 17 and above. The code is concise and errors are handled through exceptions. The C 17 standard must be enabled; 3. On POSIX systems, the stat() function can be used to efficiently obtain file size, which is suitable for performance-sensitive scenarios. The appropriate method should be selected based on the compiler and platform, and std::filesystem should be used first (if available), otherwise use ifstream to ensure compatibility, or use st on Unix systems

Operator overloading in C allows new behaviors of standard operators to be assigned to custom types, 1. Return new objects through member function overloading; 2. Overload = Modify the current object and return reference; 3. Friend function overloading

To use regular expressions in C, you need to include header files and use the functions it provides for pattern matching and text processing. 1. Use std::regex_match to match the full string, and return true only when the entire string conforms to the pattern; 2. Use std::regex_search to find matches at any position in the string; 3. Use std::smatch to extract the capture group, obtain the complete match through matches[0], matches[1] and subsequent sub-matches; 4. Use std::regex_replace to replace the matching text, and support the capture group with references such as $1 and $2; 5. You can add an iset when constructing the regex (