Скачать или смотреть Resolving the redeclared as different kind of symbol Error When Using typedef in C

Learn how to fix the common C programming error of re-declaring function types by using proper naming conventions and structuring your typedefs effectively.
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Understanding the redeclared as different kind of symbol Error

Programming in C can sometimes lead to frustrating errors, especially when dealing with type definitions and function declarations. One such error that many developers encounter is: "redeclared as different kind of symbol." This issue often arises when function names and type names conflict, leading to confusion for the compiler.

In this guide, we'll explore the root cause of this error, particularly in the context of a UART driver and a GSM module, and we'll guide you through an effective solution.

The Problem

Consider the following snippets of code: one defines functions related to UART communication, while the other sets up callback function pointers for a SIM900 GSM module. The issue arises when both code snippets attempt to use the same names for function pointers and functions, such as USART_Init, USART_SendString, and USART_TxChar.

Upon compiling, you might encounter errors like:

USART_Init redeclared as different kind of symbol

USART_SendString redeclared as different kind of symbol

USART_TxChar redeclared as different kind of symbol

These errors indicate a naming conflict because the compiler cannot decipher whether you're referring to a function or a typedef for a function.

The Solution

The key to resolving this issue lies in proper naming conventions and clarity in the code. Here’s how you can address the problem:

1. Rename the Typedefs

To avoid the conflict, you can change the type names to something that doesn't clash with existing function names. Adding a suffix, such as _cb (for callbacks) or _f (for functions), helps indicate the purpose of the type clearly.

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2. Use Structs for Function Pointers

Instead of typedefs for the function pointers themselves, consider creating typedefs for the functions. This way, when you refer to function pointers in a struct, it becomes more organized and less prone to conflict.

Here's an improved version of the typedefs, encapsulated within a structure:

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Benefits of This Approach

Clarity: By distinguishing between a function and a function pointer, the code is easier to understand.

Minimized Conflicts: Using precise naming conventions significantly reduces the likelihood of symbol conflicts during compilation.

Conclusion

In C programming, particularly when dealing with complex systems like UART and GSM modules, clarity and organization in your code are crucial. By renaming your typedefs and considering the context of your structures, you not only resolve errors but also enhance the maintainability of your code.

Remember, effective naming conventions can save you a lot of headaches down the line. Happy coding!