What should I pay attention to when using C++ inline functions?

C Inline functions are expanded directly at compile time to avoid function call overhead. Things to note include: 1. Keep the function body small (within 10 lines recommended); 2. Avoid loops and recursions; 3. Note that inline expansion only occurs within the scope of the same file. In the actual case, the inline function for calculating the area of ​​a triangle replaces the ordinary function, which reduces the function call overhead and improves the program performance.

C Inline functions: matters and practical cases

Inline functions are functions that are directly expanded at compile time, and their code Will be embedded into the calling site, avoiding the overhead of function calls. When using C inline functions, you need to pay attention to the following:

1. The function body cannot be too large

The inline function is expanded at the calling point. If the function body is too large If it is large, it will increase the size of the generated code, affecting readability and compilation speed. Generally speaking, it is recommended that the number of lines of code for inline functions be controlled within 10 lines.

2. Avoid loops and recursions

After inline function expansion, if loops or recursions are included, the code will be repeatedly expanded, causing code bloat and performance problems. Try to avoid using loops or recursion in inline functions.

3. Pay attention to the scope of inline expansion

Inline functions are only expanded within the scope of the same file, and inline functions in different files will not be expanded. Therefore, when calling a cross-file inline function, you need to carefully consider whether to declare it inline.

Practical case

Suppose we have a function that calculates the area of ​​a triangle:

double calculate_area_triangle(double base, double height) {
  return 0.5 * base * height;
}

We can declare it as an inline function:

inline double calculate_area_triangle(double base, double height) {
  return 0.5 * base * height;
}

In the main function, we can call the inline function like this:

int main() {
  double base = 10.0;
  double height = 5.0;
  double area = calculate_area_triangle(base, height);
  std::cout << "Area of the triangle: " << area << std::endl;
  return 0;
}

Because the function body is less than 10 lines and does not contain loops or recursions, inline expansion can effectively reduce the cost of function calls. Improve program performance.

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