How to convert enum names to string in c

Question

Is there a possibility to convert enumerator names to string in C

User · Answer

I usually do this    define COLOR STR color                                    RED          color    red                              BLUE        color    blue                              GREEN      color    green                              YELLOW    color    yellow     unknown

User · Answer

There is no simple way to achieves this directly  But P99 has macros that allow you to create such type of function automatically    P99 DECLARE ENUM color  red  green  blue     in a header file  and   P99 DEFINE ENUM color     in one compilation unit   c file  should then do the trick  in that example the function then would be called color getname

User · Answer

A function like that without validating the enum is a trifle dangerous  I suggest using a switch statement  Another advantage is that this can be used for enums that have defined values  for example for flags where the values are 1 2 4 8 16 etc   Also put all your enum strings together in one array -  static const char   allEnums            Undefined        apple        orange         etc         define the indices in a header file -   define ID undefined       0  define ID fruit apple     1  define ID fruit orange    2    etc      Doing this makes it easier to produce different versions  for example if you want to make international versions of your program with other languages   Using a macro  also in the header file -   define CASE type val  case val  index   ID   type     val  break    Make a function with a switch statement  this should return a const char   because the strings static consts -  const char   FruitString enum fruit e        unsigned int index       switch e           CASE fruit  apple          CASE fruit  orange          CASE fruit  banana             etc            default  index   ID undefined            return allEnums index       If programming with Windows then the ID  values can be resource values    If using C   then all the functions can have the same name   string EnumToString fruit e

User · Answer

An simpler alternative to Hokyo s  Non-Sequential enums  answer  based on using designators to instantiate the string array    define NAMES C RED  10 C GREEN  20 C BLUE  30   define C k  v  k   v  enum color   NAMES     undef C   define C k  v   v     k      const char   const color name       NAMES

User · Answer

I found a C preprocessor trick that is doing the same job without declaring a dedicated array string  Source  http   userpage fu-berlin de  ram pub pub jf47ht81Ht c preprocessor applications en    Sequential enums  Following the invention of Stefan Ram  sequential enums  without explicitely stating the index  e g  enum  foo -1  foo1   1   can be realized like this genius trick    include  lt stdio h gt    define NAMES C RED C GREEN C BLUE   define C x  x  enum color   NAMES TOP     undef C   define C x   x      const char   const color name       NAMES      This gives the following result   int main  void           printf   The color is  s  n   color name  RED           printf   There are  d colors  n   TOP            The color is RED    There are 3 colors    Non-Sequential enums  Since I wanted to map error codes definitions to are array string  so that I can append the raw error definition to the error code  e g   The error is 3  LC FT DEVICE NOT OPENED      I extended the code in that way that you can easily determine the required index for the respective enum values    define LOOPN n a  LOOP  n a   define LOOPF    define LOOP2 a  a LOOPF a LOOPF  define LOOP3 a  a LOOPF a LOOPF a LOOPF  define LOOP4 a  a LOOPF a LOOPF a LOOPF a LOOPF  define LOOP5 a  a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF  define LOOP6 a  a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF  define LOOP7 a  a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF  define LOOP8 a  a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF  define LOOP9 a  a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF a LOOPF    define LC ERRORS NAMES       Cn LC RESPONSE PLUGIN OK  -10        Cw 8        Cn LC RESPONSE GENERIC ERROR  -1        Cn LC FT OK  0        Ci LC FT INVALID HANDLE        Ci LC FT DEVICE NOT FOUND        Ci LC FT DEVICE NOT OPENED        Ci LC FT IO ERROR        Ci LC FT INSUFFICIENT RESOURCES        Ci LC FT INVALID PARAMETER        Ci LC FT INVALID BAUD RATE        Ci LC FT DEVICE NOT OPENED FOR ERASE        Ci LC FT DEVICE NOT OPENED FOR WRITE        Ci LC FT FAILED TO WRITE DEVICE        Ci LC FT EEPROM READ FAILED        Ci LC FT EEPROM WRITE FAILED        Ci LC FT EEPROM ERASE FAILED        Ci LC FT EEPROM NOT PRESENT        Ci LC FT EEPROM NOT PROGRAMMED        Ci LC FT INVALID ARGS        Ci LC FT NOT SUPPORTED        Ci LC FT OTHER ERROR        Ci LC FT DEVICE LIST NOT READY     define Cn x y  x y   define Ci x  x   define Cw x  enum LC errors   LC ERRORS NAMES TOP     undef Cn  undef Ci  undef Cw  define Cn x y   x   define Ci x   x   define Cw x  LOOPN x     static const char    LC errors  strings       LC ERRORS NAMES    static const char   LC errors  strings    amp   LC errors  strings 10     In this example  the C preprocessor will generate the following code    enum LC errors   LC RESPONSE PLUGIN OK -10   LC RESPONSE GENERIC ERROR -1  LC FT OK 0  LC FT INVALID HANDLE  LC FT DEVICE NOT FOUND  LC FT DEVICE NOT OPENED  LC FT IO ERROR  LC FT INSUFFICIENT RESOURCES  LC FT INVALID PARAMETER  LC FT INVALID BAUD RATE  LC FT DEVICE NOT OPENED FOR ERASE  LC FT DEVICE NOT OPENED FOR WRITE  LC FT FAILED TO WRITE DEVICE  LC FT EEPROM READ FAILED  LC FT EEPROM WRITE FAILED  LC FT EEPROM ERASE FAILED  LC FT EEPROM NOT PRESENT  LC FT EEPROM NOT PROGRAMMED  LC FT INVALID ARGS  LC FT NOT SUPPORTED  LC FT OTHER ERROR  LC FT DEVICE LIST NOT READY  TOP     static const char    LC errors  strings        LC RESPONSE PLUGIN OK                                          LC RESPONSE GENERIC ERROR    LC FT OK    LC FT INVALID HANDLE    LC FT DEVICE NOT FOUND    LC FT DEVICE NOT OPENED    LC FT IO ERROR    LC FT INSUFFICIENT RESOURCES    LC FT INVALID PARAMETER    LC FT INVALID BAUD RATE    LC FT DEVICE NOT OPENED FOR ERASE    LC FT DEVICE NOT OPENED FOR WRITE    LC FT FAILED TO WRITE DEVICE    LC FT EEPROM READ FAILED    LC FT EEPROM WRITE FAILED    LC FT EEPROM ERASE FAILED    LC FT EEPROM NOT PRESENT    LC FT EEPROM NOT PROGRAMMED    LC FT INVALID ARGS    LC FT NOT SUPPORTED    LC FT OTHER ERROR    LC FT DEVICE LIST NOT READY        This results to the following implementation capabilities      LC errors  strings -1         LC errors  strings LC RESPONSE GENERIC ERROR          LC RESPONSE GENERIC ERROR

User · Answer

In a situation where you have this   enum fruit       apple       orange       grape      banana         etc       I like to put this in the header file where the enum is defined   static inline char  stringFromFruit enum fruit f        static const char  strings        apple    orange    grape    banana      continue for rest of values            return strings f

User · Answer

You don t need to rely on the preprocessor to ensure your enums and strings are in sync  To me using macros tend to make the code harder to read   Using Enum And An Array Of Strings  enum fruit                                                                          APPLE   0       ORANGE       GRAPE      BANANA         etc         FRUIT MAX                                                                                                                        const char   const fruit str            BANANA     banana        ORANGE     orange        GRAPE      grape        APPLE      apple          etc            Note  the strings in the fruit str array don t have to be declared in the same order as the enum items    How To Use It  printf  enum apple as a string   s n   fruit str APPLE      Adding A Compile Time Check  If you are afraid to forget one string  you can add the following check    define ASSERT ENUM TO STR sarray  max                                             typedef char assert sizeof   max  sizeof sarray  sizeof sarray 0       max     1   -1   ASSERT ENUM TO STR fruit str  FRUIT MAX     An error would be reported at compile time if the amount of enum items does not match the amount of strings in the array

User · Answer

One way  making the preprocessor do the work  It also ensures your enums and strings are in sync    define FOREACH FRUIT FRUIT            FRUIT apple              FRUIT orange             FRUIT grape              FRUIT banana       define GENERATE ENUM ENUM  ENUM   define GENERATE STRING STRING   STRING   enum FRUIT ENUM       FOREACH FRUIT GENERATE ENUM      static const char  FRUIT STRING           FOREACH FRUIT GENERATE STRING       After the preprocessor gets done  you ll have   enum FRUIT ENUM       apple  orange  grape  banana      static const char  FRUIT STRING            apple    orange    grape    banana        Then you could do something like   printf  enum apple as a string   s n  FRUIT STRING apple      If the use case is literally just printing the enum name  add the following macros    define str x   x  define xstr x  str x    Then do   printf  enum apple as a string   s n   xstr apple      In this case  it may seem like the two-level macro is superfluous  however  due to how stringification works in C  it is necessary in some cases  For example  let s say we want to use a  define with an enum    define foo apple  int main         printf   s n   str foo        printf   s n   xstr foo        The output would be   foo apple   This is because str will stringify the input foo rather than expand it to be apple  By using xstr the macro expansion is done first  then that result is stringified    See Stringification for more information

[c] How to convert enum names to string in c

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