Why Are Exception Specifications in Function Signatures Considered a Poor Practice?

Exception Specification in Function Signature: A Poor Practice

The usage of the 'throw' keyword in a function's signature has been discouraged due to several technical drawbacks.

Consider the following function definition:

<code class="cpp">bool some_func() throw(myExc) { ... }</code>

Here, the exception specification indicates that the function may throw an exception of type 'myExc'. However, this specification has limitations:

• Compiler Enforcement: The compiler cannot strictly enforce the specified exception, leading to potential runtime errors. If the function throws an unexpected exception, runtime checks are required, which is inefficient and prone to issues.
• Limited Support: The exception specification is not supported consistently across compilers. For instance, MSVC interprets this specification as a guarantee that no exceptions will be thrown, regardless of the actual behavior of the function.
• Restricted Functionality: The 'throw' specification in a function signature restricts the type of exceptions that can be thrown. This can limit the flexibility and extensibility of the code, as it may not always be possible to anticipate all potential exceptions.

Therefore, it is generally considered good practice to avoid using the 'throw' keyword in function signatures. Instead, exceptions should be thrown from within the function body, where they can be properly handled and documented.

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