std::nothrow in C++

In this article, we will discuss std:nothrow in C++ with its syntax, parameters, examples, and advantages. It allows us to break from the monotony of using the syntax that comes with the language and create codes that are simpler, more intuitively structured, and high-level.

What is the std::nothrow in C++?

In C++, the std::nothrow will be set up beside the new operator in order to point to the allocation operation failure that will not lead to an exception throwing. It forms part of the header and is a replacement for a memory allocation error.

By default, when the new operator is used to allocate memory, it throws an exception of type std::bad_alloc is used for situations when the allocation process fails. Therefore, an appropriate exception handler can be used to resolve the current problem in this situation. Although there are many cases when you manage it, certain areas need exceptions than others.

The std::nothrow will execute this task accordingly. When we use std::nothrow, it adds a new operation that returns a null pointer (nullptr) rather than throwing an exception if allocation fails. Therefore, we have the option to verify the returned pointer and handle failure gracefully without using exceptions.

Syntax:

It has the following syntax:

The above code "T" stands for the type of object that we would want to allocate. Adding (std::nothrow) right after the new keyword shows the compiler that the new operator with a no-throw feature should be used.

The allocator initializes the pointer, and if it is successful, the pointer is going to be pointed to be the container of the type defined as the argument of the constructor. Otherwise, the pointer holds some amount of namespace, and it shows null.

Example:

Let's take an example that demonstrates the usage of std::nothrow in C++.

Filename: Nothrow.cpp

Output:

Explanation:

• In this example, the main() function is the first function that the program will run. When the program starts, it begins by printing the message "The Allocation process........" to the console using std:cout << "The Allocation process ..........";.
• Next, an input character pointer pts is defined. This variable is not initialized at this time.
• The line char* pts = new (std::nothrow) char[1024 * 1024]; is located in a memory block of 1 megabyte size, with std::nothrow new operator. The std::nothrow qualifier says that the allocated memory should be returned as a null pointer in the event of a failure of the allocation instead of throwing an exception.
• After that, the program begins to examine the allocated space by comparing pts and 0 (i.e., nullptr). If the pointer is nullptr, it means the allocation failed, and the program prints the message "Failure!\n" to the console using std:cout << "Failure!\n";
• Successful operation (i.e., the pointer is not nullptr) means that the program continues to follow the else segment of the flowchart. It prints the message "Success!\n" to the console using std:cout<<"Success\n";

Advantages of std::nothrow in C++

Several advantages of the std::nothrow function in C++.

• Exception Safety: The main goal of std::nothrow is to present a no-throw guarantee for memory allocation. It means that when we use new with std::nothrow, it will return a valid pointer to the allocated memory or a null pointer ( nullptr). It can be helpful in some situations where we want to avoid exceptions or a very specific way of handling memory allocation failures.
• Alternative to Exception Handling: Exception handling in C++ is a great option to handle errors and any unanticipated condition. On the other hand, in some cases the exception might be not desirable or is support in embedded systems or specific performance-critical applications. The std::nothrow offers an approach for memory managers to deal with allocation failures other than using exceptions.
• Memory Allocation Failure: memory allocation also fails when the std::nothrow new operator is used, which returns nullptr as the pointer. It is very imperative to use the proper domain of memory.
• Resource Management: The std::nothrow keyword should be used instead of the new operator At the same time, we should use the delete to release the allocated memory. If it is not done, a memory leak will be the outcome. We can use the "delete" keyword as we usually do, irrespective of whether the allocation has been successful or not.
• Limitations: The std::nothrow calls prevent exceptions from being thrown when out-of-memory error occurs. However, this method cannot be used for other errors occurring during object construction. If the constructor of the object being allocated throws an exception, it cannot be caught or handled using std::nothrow. In such cases, an exception will still be thrown, regardless of the use of std::nothrow.
• Usage Considerations: Generally, exceptions should be employed for error handling unless we have exceptional circumstances not to use them. Using exceptions allows us to channel the error handling in a more structured and flexible way. The std::nothrow is mostly used in special cases where exceptions are not adequate or in context with other error-handling approaches.

Conclusion:

In conclusion, std::nothrow in C++ is a mechanism that assigns the memory without throwing an exception in case of failure. By using std::nothrow without a new operator, programmers can achieve memory allocation error handling without the use of exception handling mechanisms anymore. This approach ensures exception safety and maybe a substitute for traditional exception handling; the reason is that it is suitable in situations where exceptions are not desirable, and performance-conscious applications may require a different error-handling method. However, it's important to note that std::nothrow has some troubles like if the object is constructed, an exception cannot be handled. Therefore, this instance should be particularly considered in terms of cases and requirements. Overall, the std::nothrow allows system designers to predict and handle errors in memory allocation, which contributes to building robust and predictable software.