Understanding the Differences Between consteval Wrapper and source_location in C+ + 20 скачать в хорошем качестве

Understanding the Differences Between consteval Wrapper and source_location in C+ + 20

Explore why using `consteval` with `std::experimental::source_location` behaves unexpectedly in your C+ + 20 projects and how to resolve it effectively. --- This video is based on the question https://stackoverflow.com/q/62628942/ asked by the user 'Silicomancer' ( https://stackoverflow.com/u/1421332/ ) and on the answer https://stackoverflow.com/a/73569132/ provided by the user 'Silicomancer' ( https://stackoverflow.com/u/1421332/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions. Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: consteval wrapper vs. source_location Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l... The original Question post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 4.0' ( https://creativecommons.org/licenses/... ) license. If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com. --- Understanding the Differences Between consteval Wrapper and source_location in C+ + 20 In the journey of learning and mastering C+ + , you may come across some intriguing challenges, especially with new features introduced in C+ + 20. One such issue arises when you're trying to use consteval to create a wrapper around std::experimental::source_location. Many developers, like yourself, have faced unexpected output, leading to a bit of confusion about the behavior of consteval. In this guide, we will clarify these issues and provide an insightful breakdown of the solution. The Problem Explained Code Example 1: First Variant You set up the following code to get the current line number using consteval: [[See Video to Reveal this Text or Code Snippet]] Expected vs. Actual Output You expected to see the output reflecting the line numbers from the actual calls: [[See Video to Reveal this Text or Code Snippet]] However, you received: [[See Video to Reveal this Text or Code Snippet]] Code Example 2: Second Variant After encountering this unexpected result, you tried a different approach: [[See Video to Reveal this Text or Code Snippet]] Expected vs. Actual Output Again, your expectation was for the output: [[See Video to Reveal this Text or Code Snippet]] Instead, you received: [[See Video to Reveal this Text or Code Snippet]] The Root of the Confusion The discrepancies in the outputs stem from how consteval behaves in conjunction with the std::experimental::source_location. The key takeaway here is that consteval enforces immediate evaluation, which interferes with the expected line tracking provided by source_location. This does mean that the initial current position of the code gets recorded instead of reflecting the intended call site. The Solution: Why constexpr or inline Works Ideal Approach Upon updating your code to use constexpr or inline instead of consteval, you found that this produced the expected behavior across recent versions of GCC. Here’s a concise breakdown of why this approach works: constexpr and inline: These keywords allow the function to be evaluated at the call site across different contexts without losing the intended line information. Runtime Evaluation vs. Compile-time Evaluation: While consteval demands evaluation during compilation, using these alternatives provides flexibility in evaluation, aiding in correct line tracking. Example Solution Here's how you can adjust your code for clarity and accuracy using constexpr: [[See Video to Reveal this Text or Code Snippet]] With this modification, your output will correctly reflect the line numbers as you intended. Conclusion Understanding the nuances between consteval and std::experimental::source_location is crucial for mastering C+ + . This experience is a prime example of why closely observing the compiler's behavior with new standards is vital. In practice, opting for constexpr or inline will ensure that your code behaves as expected without confounding issues. If you encounter similar challenges, remember to experiment with different types of evaluations, and don’t hesitate to consult documentation or community insights for richer knowledge and understanding. Happy coding!