What are the application scenarios of C++ inline functions?

Inline functions are C functions that are directly inserted into the calling code, eliminating the need for function calls and improving performance. Its application scenarios include: small functions on the performance critical path, frequently called functions, tail recursive functions and template functions. For example, inlining functions can eliminate function call overhead and increase speed when calculating factorials.

C Inline function: application scenarios and practical cases

Inline function is a special type of function in C. It is inserted directly into the code that calls it, rather than being called as a separate function. This improves performance by eliminating the overhead of function calls.

Application scenarios:

• #Small functions on the performance critical path: Inline functions are especially suitable for small functions on the performance critical path Functions such as mathematical operations, logical comparisons, and data access.
• Frequently called functions: If a function is called frequently, inlining it can significantly reduce the overhead of function calls and improve overall performance.
• Tail recursive function: Inline tail recursive function can eliminate the stack overhead of recursive functions and improve performance.
• Template function: Inline template function can optimize the execution speed of template code, because the compiler can directly generate inline code based on specific type parameters.

Practical case:

The following is a sample code showing the application of inline functions in calculating factorials:

#include <iostream>

// 标准的 C++ 函数
int factorial(int n) {
    if (n == 0) {
        return 1;
    }
    else {
        return n * factorial(n - 1);
    }
}

// 内联函数
inline int inlineFactorial(int n) {
    if (n == 0) {
        return 1;
    }
    else {
        return n * inlineFactorial(n - 1);
    }
}

int main() {
    // 普通函数
    std::cout << "阶乘 (5): " << factorial(5) << std::endl;

    // 内联函数
    std::cout << "阶乘 (5): " << inlineFactorial(5) << std::endl;

    return 0;
}

Output:

阶乘 (5): 120
阶乘 (5): 120

In this example, the inline function inlineFactorial executes faster than the normal function factorial because the function call overhead is eliminated .

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