C ++ pit essays

Header defined to prevent duplicate

1. There are two methods, namely,

   #ifndef xxx_h
   #define xxx_h
   ...
   #endif

   #pragma once

Header files have been using the above method still multiple define

1. Note that the header files only statement can not be defined, otherwise an error
2. Static variable initialization method c ++ class members in private

//.h文件
class Test{
 static double A; 
 static double B();
};
//.cpp文件
double Test::A= 2.0; //正确的静态成员初始化

vector

erase operation

• Principle: the removal process covering the back of the iter for the specified data all move forward

• Note the point: the deleted position after deleting iter may become dangling pointers (if iter is the last one) so for this case to properly handle

• Test code

#include <vector>
#include <cstdio>
using namespace std;


int main(){
    vector <int> a;
    a.clear();
    a.push_back(1);
    a.push_back(2);
    a.push_back(3);
    
    for(int i = 0; i < a.size(); i++)
        printf("%d ", a[i]);
        
    vector<int>::iterator itr = a.begin();
    a.erase(itr+1);
    
    for(int i = 0; i < a.size(); i++)
        printf("%d ", a[i]);         
}

Catch2 test framework SECTION

During a large amount of test data, SECTION enter an infinite loop state, could not get out, breakpoints can not locate the problem, after changing operating normally run directly to TEST_CASE, the problem is unknown, speculation and function related to memory limitations.