Typedef redefinition with different types (‘uint8_t’ (aka ‘unsigned char’) vs ‘enum clockid_t’)

When you encounter the error message “typedef redefinition with different types (‘uint8_t’ (aka ‘unsigned char’) vs ‘enum clockid_t’)”, it means that there is a conflict between two different types that are being typedef’ed with the same name.

The error specifically mentions the types involved in the conflict: ‘uint8_t’ and ‘enum clockid_t’. ‘uint8_t’ is a typedef for an unsigned char, while ‘enum clockid_t’ is an enumeration type.

To understand this error better, let’s consider an example. Suppose you have two header files in your codebase, each defining a typedef for ‘clockid_t’ in a different way:

    
      // File 1: typedef1.h
      typedef unsigned char clockid_t;

      // File 2: typedef2.h
      typedef enum {
          CLOCK_REALTIME,
          CLOCK_MONOTONIC
      } clockid_t;
    
  

In this case, when you include both header files in the same source file, you will encounter the “typedef redefinition” error. This error occurs because the compiler is trying to typedef ‘clockid_t’ with two different types (‘unsigned char’ and the enumeration).

To resolve this error, you need to remove the conflicting typedefs or find a way to use them without naming conflicts. Here are a few possible solutions:

1. Rename one of the typedefs: You can rename either ‘uint8_t’ or ‘enum clockid_t’ to avoid the conflict. For example:

           
             // File 1: typedef1.h
             typedef unsigned char my_clockid_t;
   
             // File 2: typedef2.h
             typedef enum {
                 CLOCK_REALTIME,
                 CLOCK_MONOTONIC
             } clockid_t;
           
         

   Now you can use ‘my_clockid_t’ and ‘clockid_t’ separately without conflicts.

2. Modify the conflicting typedef: If you have control over the header files, you can modify one of the typedefs to match the other. In our example, you can modify ‘typedef unsigned char clockid_t;’ to ‘typedef enum clockid_t clockid_t;’. This aligns both typedefs to refer to the enumeration type.

           
             // File 1: typedef1.h
             typedef enum clockid_t clockid_t;
   
             // File 2: typedef2.h
             typedef enum {
                 CLOCK_REALTIME,
                 CLOCK_MONOTONIC
             } clockid_t;
           
         

   Now both typedefs refer to the same enumeration type and can be used without conflicts.

By resolving the typedef conflict, you can eliminate the “typedef redefinition with different types” error and ensure that your code compiles successfully.