Re: enum vs int and API/ABI compatibility

[Bruno Haible]

Hi Simon,

> silence C++ warnings ...
> 
>   typedef enum
>   {
> ...
>   } Idna_rc;
> ...
>   extern IDNAPI const char *idna_strerror (Idna_rc rc);
> 
> ... allows future C++ code to be warning free.

It was said that the root problem is that your idna_* functions
return an 'int', but idna_strerror takes an Idna_rc. This is
inconsistent.

There are three ways to fix this in a way that gets rid of the C++ warnings:

1) Change the return types from 'int' to 'Idna_rc'. Keep the enum as it is.

2) Change the argument type of idna_strerror to 'int'. Change the enum
   from

     typedef enum {
       ...
       IDNA_ICONV_ERROR = 9,
       ...
     } Idna_rc;

   to

     typedef int Idna_rc;
     #ifdef __cplusplus
     /* In C++ we avoid macros.  */
     ...
     const int IDNA_ICONV_ERROR = 9;
     ...
     #else
     ...
     #define IDNA_ICONV_ERROR 9
     ...
     #endif

3) Keep the inconsistency as it is for C, but fix it for C++ only.
   Change the enum from

     typedef enum {
       ...
       IDNA_ICONV_ERROR = 9,
       ...
     } Idna_rc;

   to

     #ifdef __cplusplus
     typedef int Idna_rc;
     /* In C++ we avoid macros.  */
     ...
     const int IDNA_ICONV_ERROR = 9;
     ...
     #else
     typedef enum {
       ...
       IDNA_ICONV_ERROR = 9,
       ...
     } Idna_rc;
     #endif


Bruno
-- 
In memoriam Jerzy Popiełuszko <http://en.wikipedia.org/wiki/Jerzy_Popiełuszko>