[Xcb] [PATCH Xcb] Added more error states and removed global error_connection

[Uli Schlachter]

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On 04.11.2011 14:36, Arvind Umrao wrote:
> I have added more xcb connection errorstates at xcb.h header.
> Also I have removed global error_connection variable and added
> an interface that returns connection error state.
> 
> As Uli Schlachter suggested, I have added seperate static variable for
> every possible error at _xcb_conn_ret_error() to make thread safe.
> 
> TBD:
> I will segregate errors states in a separate header file and try to
> provide more precise error states, in future. Also I will give patch
> for libX11, in that patch xcb_connection_t::has_error will be passed
> to default io handler of libX11, This value can then be used for
> displaying error messages.
> 
> Signed-off-by: Arvind Umrao <arvind.umrao at oracle.com>
> ---

[...]
> +/* Return connection error state.
> + * To make thread-safe, I need a seperate static
> + * variable for every possible error.
> + */
> +xcb_connection_t *_xcb_conn_ret_error(int err)
> +{
> +    
> +    switch(err)
> +    {
> +        case XCB_CONN_CLOSED_MEM_INSUFFICIENT:
> +        {
> +            static int error_mem;
> +            error_mem = err;
> +            return (xcb_connection_t *) &error_mem;
> +        }
> +        case XCB_CONN_CLOSED_PARSE_ERR:
> +        {
> +            static int error_parser;
> +            error_parser = err;
> +            return (xcb_connection_t *) &error_parser;
> +        }
> +        case XCB_CONN_ERROR:
> +        default:
> +        {
> +            static int error_connection;
> +            error_connection = XCB_CONN_ERROR;
> +            return (xcb_connection_t *) &error_connection;
> +        }
> +    }
>  }
[...]

I just noticed that this assumes that writing to an int is atomic (=reading it
at the same time will either return the old or the new value, but never
garbage). I don't know which arches don't have atomic stores, but I know that I
saw "#ifdef"s in other projects for that.

Can't this be turned into:

  static int error_mem = XCB_CONN_CLOSED_MEM_INSUFFICIENT;

(And perhaps be moved out of this function into global context, but I know that
this isn't going to happen due to some broken compiler on solaris(?)...)

Anyone could enlighten me if there are actually arches on which this code would
break?

Uli

- -- 
"Do you know that books smell like nutmeg or some spice from a foreign land?"
                                                  -- Faber in Fahrenheit 451
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