Differences in C++ function default parameters and variable parameters in different compilers

Default parameters allow functions to use default values, supported in C 11 and above, using different syntax in Visual Studio. Variadics allow functions to receive variable arguments. Supported in C 11 and above. Not supported in Visual Studio. Special syntax is required in GCC.

Differences in C function default parameters and variable parameters in different compilers

Default parameters

Default parameters allow functions to use predefined values ​​when the corresponding parameters are not provided. C 11 and later supports default parameters.

In Visual Studio, you can specify default parameters using the following syntax:

int AddNumbers(int a, int b = 10) {
  return a + b;
}

In GCC, use the following syntax:

int AddNumbers(int a, int b = 10) __attribute__((deprecated));

Variable parameters

Variable parameters allow a function to receive an indefinite number of parameters. C 11 and later supports variadic arguments.

In Visual Studio, you can use ... to represent variable parameters:

void PrintNumbers(int n, ...) {
  va_list args;
  va_start(args, n);
  for (int i = 0; i < n; i++) {
    cout << va_arg(args, int) << " ";
  }
  va_end(args);
}

In GCC, use the following syntax:

void PrintNumbers(int n, ...) __attribute__((deprecated));

Actual case

Default parameter case:

int main() {
  // 使用默认参数
  int sum1 = AddNumbers(5); // sum1 为 15
  
  // 不使用默认参数
  int sum2 = AddNumbers(5, 20); // sum2 为 25
  
  return 0;
}

Variable parameter case:

int main() {
  // 声明并初始化可变参数列表
  int n = 5;
  int numbers[] = {1, 2, 3, 4, 5};
  
  // 使用可变参数函数打印数字
  PrintNumbers(n, numbers); // 输出：1 2 3 4 5
  
  return 0;
}

Note

• Visual Studio does not yet support variadic parameters, so code generated in GCC will not compile in Visual Studio.
• __attribute__((deprecated)) in the default parameter indicates that the feature is deprecated but is still supported. Please use caution when using.

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