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Gabriel Staples
6 Dec. 2019
Demonstrate how to handle errors in C, using enums and a function to convert these enums to printable strings.
See also: https://stackoverflow.com/questions/385975/error-handling-in-c-code
*******************************************************************************/
// ---------------
// mymodule.h
// ---------------
/// Get the number of elements in any C array
/// - Usage example: [my own answer]:
/// https://arduino.stackexchange.com/a/80289/7727
#define ARRAY_LEN(array) (sizeof(array) / sizeof((array)[0]))
/// @brief Error codes for library "mymodule"
typedef enum mymodule_error_e
{
/// No error
MYMODULE_ERROR_OK = 0,
/// Invalid arguments (ex: NULL pointer where a valid pointer is required)
MYMODULE_ERROR_INVARG,
/// Out of memory (RAM)
MYMODULE_ERROR_NOMEM,
/// Make up your error codes as you see fit
MYMODULE_ERROR_MYERROR,
// etc etc
/// Total # of errors in this list (NOT AN ACTUAL ERROR CODE);
/// NOTE: that for this to work, it assumes your first error code is value 0 and you let it naturally
/// increment from there, as is done above, without explicitly altering any error values above
MYMODULE_ERROR_COUNT,
} mymodule_error_t;
// Array of strings to map enum error types to printable strings
// - see important NOTE above!
const char* const MYMODULE_ERROR_STRS[] =
{
"MYMODULE_ERROR_OK",
"MYMODULE_ERROR_INVARG",
"MYMODULE_ERROR_NOMEM",
"MYMODULE_ERROR_MYERROR",
};
_Static_assert(ARRAY_LEN(MYMODULE_ERROR_STRS) == MYMODULE_ERROR_COUNT,
"You must keep your `mymodule_error_t` enum and your "
"`MYMODULE_ERROR_STRS` array in-sync!");
// To get a printable error string
const char* mymodule_error_str(mymodule_error_t err);
// Other functions in mymodule
mymodule_error_t mymodule_func1(void);
mymodule_error_t mymodule_func2(void);
mymodule_error_t mymodule_func3(void);
// ---------------
// mymodule.c
// ---------------
#include <stdio.h>
/// @brief Function to get a printable string from an enum error type
/// @param[in] err a valid error code for this module
/// @return A printable C string corresponding to the error code input above, or NULL if an invalid error code
/// was passed in
const char* mymodule_error_str(mymodule_error_t err)
{
const char* err_str = NULL;
// Ensure error codes are within the valid array index range
if (err >= MYMODULE_ERROR_COUNT)
{
goto done;
}
err_str = MYMODULE_ERROR_STRS[err];
done:
return err_str;
}
// Let's just make some empty dummy functions to return some errors; fill these in as appropriate for your
// library module
mymodule_error_t mymodule_func1(void)
{
return MYMODULE_ERROR_OK;
}
mymodule_error_t mymodule_func2(void)
{
return MYMODULE_ERROR_INVARG;
}
mymodule_error_t mymodule_func3(void)
{
return MYMODULE_ERROR_MYERROR;
}
// ---------------
// main.c
// ---------------
#include <stdio.h>
int main()
{
printf("Demonstration of enum-based error codes in C (or C++)\n");
printf("err code from mymodule_func1() = %s\n", mymodule_error_str(mymodule_func1()));
printf("err code from mymodule_func2() = %s\n", mymodule_error_str(mymodule_func2()));
printf("err code from mymodule_func3() = %s\n", mymodule_error_str(mymodule_func3()));
return 0;
}