[GRASS-dev] is this compiler-safe?

[Markus Metz]

Paul Kelly wrote:
> Markus Metz wrote:
>
>>
>> should
>>   if (lseek(fd, 0L, SEEK_SET) == (off_t) - 1) {
>>
>> not be
>>   if (lseek(fd, 0L, SEEK_SET) == (off_t) -1) {
>>
>
> Hello Markus,
> Well, looks like a bug in the indent program that got confused by the 
> cast and thought the - was being used as a binary rather than unary 
> operator. But is it not only an aesthetic problem? As far as I can see 
> the code should do exactly the same thing?
I am not sure if the code would do exactly the same thing with other 
compilers than gcc, but that's beyond me.
>
>>
>>   if ((bytes_wrote = write(fd, &x, sizeof(int)) == sizeof(int)) < 0)
>>
>> I am missing parentheses somewhere and would rather use
>>
>>   if ((bytes_wrote = write(fd, &x, sizeof(int))) != sizeof(int))
>>   G_warning("%s", strerror(errno));
>>
>>   return (bytes_wrote == sizeof(int));
>>
>> just to be on the safe side
>
> Yes I suppose you saw too that the code that calls this function 
> assumes if the return value is non-zero that it succeeded, which 
> doesn't seem right. I would suggest to make it even clearer by 
> removing the redundant variable x, correcting the grammar (written 
> instead of wrote) and rearranging:
>
> Index: format.c
> ===================================================================
> --- format.c    (revision 40905)
> +++ format.c    (working copy)
> @@ -170,15 +170,12 @@
>
>  static int write_int(int fd, int n)
>  {
> -    int x;
> -    int bytes_wrote;
> +    int bytes_written = write(fd, &n, sizeof(int));
>
> -    x = n;
> -
> -    if ((bytes_wrote = write(fd, &x, sizeof(int)) == sizeof(int)) < 0)
> +    if (bytes_written != sizeof(int))
>         G_warning("%s", strerror(errno));
>
> -    return bytes_wrote;
> +    return (bytes_written == sizeof(int));
>  }
>
> I think that is yet easier to read - do you agree?
Yes, that looks much better! AFAICT, ready to commit.

Markus M