Re: [RFC] Framebuffer rotation patch

[Michal Suchanek]

On 16 February 2010 22:14, address@hidden
<address@hidden> wrote:
> On Tue, Feb 16, 2010 at 3:05 PM, Michal Suchanek <address@hidden> wrote:
>> 2010/2/16 Vladimir 'φ-coder/phcoder' Serbinenko <address@hidden>:
>>> Michal Suchanek wrote:
>>>>> With typeof macro this can be made type-neutral avoiding potential 
>>>>> mistakes.
>>>>> +static inline long
>>>>> +grub_min (long x, long y)
>>>>> +{
>>>>> +  if (x > y)
>>>>> +    return y;
>>>>> +  else
>>>>> +    return x;
>>>>> +}
>>>>> +
>>>>>
>>>>
>>>> I don't see how typeof would be used. As I understand the docs it can
>>>> only set types relative to something what is already defined (and in
>>>> some cases actually dereference/call it) and there is nothing defined
>>>> at the point these functions are declared to copy the type from.
>>>>
>>> #include <stdio.h>
>>> #define swap(a,b) {typeof (a) mytemp ## __LINE__; mytemp ## __LINE__ =
>>> b; b = a; a = mytemp ## __LINE__; }
>>>
>>
>> Unlike inlines this pollutes the local namespace with unexpected
>> identifiers.. Perhaps the temporary variable should be at least
>> prefixed with an underscore or something.
>
> The braces introduce a block and the variable goes out of scope, in
> fact there's no need for __LINE__ because of this.

It breaks things when you do have a mytemp already:

$ gcc -Wall testdef.c
$ ./a.out
2 1 3 4
$ cat testdef.c
#include <stdio.h>
#define swap(a,b) {typeof (a) mytemp; mytemp = b; b = a; a = mytemp; }

int main( int argc, char ** argv)
{
  int x=1, y=2, z=3, mytemp=4;
  swap(x,y);
  swap(z,mytemp);
  return printf("%i %i %i %i\n", x, y, z, mytemp);
}

Thanks

Michal