How to solve C++ runtime error: 'invalid argument'?

How to solve C runtime error: 'invalid argument'?

When writing programs in C, we often encounter various errors. One of the common errors is the runtime error: 'invalid argument'. This error usually means that one of the parameters we passed to the function or method did not meet expectations, causing the program to fail to perform the correct operation.

So, when we encounter this error, how should we solve it? Below we will illustrate with a code example.

First, let us consider the following sample code:

#include <iostream>
#include <vector>

int main() {
    std::vector<int> nums = {1, 2, 3, 4, 5};
    int index = 10;

    int result = nums.at(index); // 这里可能会引发运行时错误

    std::cout << "Result: " << result << std::endl;

    return 0;
}

In this example, we have used a std::vector container to store some integers and try to pass them by index Access one of the elements. However, we are using an index outside the scope of the container (10), which may cause a runtime error.

When we run this code, we may get output similar to the following:

terminate called after throwing an instance of 'std::out_of_range'
  what():  vector::_M_range_check: __n (which is 10) >= this->size() (which is 5)

This is a typical 'invalid argument' runtime error. So, how should we solve it?

One way to solve this problem is to perform a bounds check before accessing the container element. We can use the member function size() provided by std::vector to get the number of elements stored in the container, and then compare it with the index to be accessed to ensure that the index is within the valid range .

The following is a modified code example:

#include <iostream>
#include <vector>

int main() {
    std::vector<int> nums = {1, 2, 3, 4, 5};
    int index = 10;

    if (index >= 0 && index < nums.size()) {
        int result = nums.at(index);
        std::cout << "Result: " << result << std::endl;
    } else {
        std::cout << "Invalid index" << std::endl;
    }

    return 0;
}

In the modified code, we added an if statement to check the validity of the index. The access operation will only be performed if the index is within the range. Otherwise, an "Invalid index" message will be output.

In this way, we can avoid the runtime error: 'invalid argument'. When we use containers such as std::vector, we must perform boundary checks to ensure that the index does not exceed the valid range of the container.

Of course, in actual programming, we will also encounter 'invalid argument' errors in various other situations. For example, when we pass an invalid pointer or reference to a function, or provide inappropriate parameters when calling a function, etc. The solutions will also vary for these situations.

In summary, when we encounter the C runtime error: 'invalid argument', we should first check the validity of the parameters to ensure that they meet the expectations of the function or method. If necessary, add safeguards such as bounds checks or input validation to avoid this type of error.

Through the above sample codes and methods, we hope to help readers better understand and solve the C runtime error: 'invalid argument', and improve the robustness and stability of the program.

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