As part of the development we have written the header file something like below
#ifndef __2023_06_21_001_H__
#define __2023_06_21_001_H__
#if (CUSTOM_FEATURE_X == CUSTOM_FEATURE_VAL)
#define CUSTOM_FEATURE_X (1u)
#define CUSTOM_FEATURE_VAL (1u)
typedef struct
{
unsigned int val;
}feature_x_t;
#endif
#endif /* __2023_06_21_001_H__ */
In a C source file, we have included the above header file. In C source file, we have declared a variable of type feature_x_t as following:
feature_x_t gl_feature_str;
In addition by mistake we have defined the both macro values inside the the header file itself as shown in snippet. We were wondering how the preprocessor, could find the feature_x_t variable type declaration which is being used in C source file.
After a day, what I understood is, it seems as both were not defined, #if (CUSTOM_FEATURE_X == CUSTOM_FEATURE_VAL), condition is passing, and the C Preprocessor processes the further declarations from the header file. Hence the variable type feature_x_t could be found.
