Using bsearch Effectively with Structs in C

A guide on correctly utilizing `bsearch` for searching through arrays of structs in C, with practical examples and explanations. --- This video is based on the question https://stackoverflow.com/q/63438117/ asked by the user 'IttayD' ( https://stackoverflow.com/u/129750/ ) and on the answer https://stackoverflow.com/a/63438264/ provided by the user 'n. m. could be an AI' ( https://stackoverflow.com/u/775806/ ) 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: Using bsearch with an array inside a struct 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. --- How to Use bsearch with Structs in C When it comes to searching through arrays in C, the bsearch function is an incredibly handy tool. However, if you’re dealing with structs and pointers, things can get a bit tricky. If you have a structured dataset and you want to find specific elements efficiently, understanding how to properly use bsearch is crucial. In this guide, we’ll explore a common problem encountered when attempting to integrate bsearch with structs and how to resolve it. The Problem: Structs and Array Pointers Imagine you have a struct defined like this: [[See Video to Reveal this Text or Code Snippet]] In this example, label_registry_t holds an array of pointers to label_t structs. Your goal is to search through this registry to find a struct based on its name. The initial attempt at using bsearch looks something like this: [[See Video to Reveal this Text or Code Snippet]] Unfortunately, this code often leads to confusing results. The comparison function receives unexpected values, leading to difficulties in finding the correct struct. Understanding the Issue The main issue stems from mismatched data types used in bsearch. The bsearch function needs to know precisely what it is searching through, as well as the specific data types of the comparison function's parameters. However, your current setup is sending an address to a label_t, while your array consists of pointers to label_t structs. Breakdown of Input Requirements To effectively use bsearch, consider the following rules: If you’re searching for an int, pass an array of int and the address of an int. If you're looking for a struct, pass an array of struct and the address of a struct. If searching for a pointer to a struct, you must pass an array of pointers to that struct and the address of the pointer. Given that your search is based on an array of pointers to label_t, your comparison function should accept two pointers to label_t pointers: [[See Video to Reveal this Text or Code Snippet]] The Correct Implementation To properly implement the search, ensure that your label_cmp function is compatible with how you're calling bsearch. But more importantly, make sure to adjust how you’re defining your search target. Instead of passing a label_t directly, you should pass in a pointer to label_t: [[See Video to Reveal this Text or Code Snippet]] Conclusion Using bsearch with structs in C is safe and efficient, but it requires understanding the various relationships between data types, pointers, and the function’s requirements. By adjusting your implementation to ensure that the comparison is compatible with what you’re passing into bsearch, you can effectively utilize this powerful searching tool. Now, you can go ahead and confidently search your struct arrays like a pro!