Re: Error-names.

["Björn Persson" <spam-away@nowhere.nil>]

Martin Klaiber wrote:

> BTW: does someone know why these constants are not recognized by the
> C-program as constants?  They are declared as constants and in the C
> header-file I put:
> 
>    /* error-codes */
> 
>    extern const int no_error_code;
>    extern const int general_error_code;
>    ...
> 
> But if I want to use it in a switch-command like that:
> 
>    int year;
>    ...
>    for (year = 2003; year <= 2005; ++year) {
>       switch (set_year (year)) {
>       case no_error_code :
>          set_lzz (1);
>          ...
>                          
> the compiler says:
> 
>    test_c.c:20: case label does not reduce to an integer constant
> 
> Is my exporting wrong?  Or is this a C-problem?  When I use "case 0"
> instead of "case no_error_code" it works ok, but this is what I want
> to avoid.

As I understand it, "const" in C doesn't give you a constant. You get 
kind of a read-only variable. You can't change its value, but it's still 
treated as a variable and not allowed where a constant is required.

Put another way, where the language requires a constant it actually 
requires a literal, not a named constant.

I suppose this is why everyone uses preprocessor macros for constants, 
since they are translated to literals.

Yet another reason to loathe C ...

-- 
Björn Persson

jor ers @sv ge.
b n_p son eri nu