[gdal-dev] RFC 31 - OGR 64bit Fields and FID

[Ari Jolma]

On 09/11/2010 03:45 AM, Joaquim Luis wrote:
>
> Hi,
>
> About the issue of the 64-bits ints on Windows we had quite some 
> troubles in GMT while implementing it.
> The problem, as far as I remember and I'm the one who suffered more 
> with it (other developers use Macs only), was that one cannot read as 
> %ld a variable that is a 64 bits int. There was no compiling or 
> running error, but memory was corrupted at totally 
> unexpected/unrelated places.
> We have a note in one of our headers that describe it, and the 
> solution we adopted
>
> /* Note: Under Windows 64-bit a 64-bit integer is __int64 and when used
>  * with scanf the format must be %lld.  This is not exactly what we call
>  * POSIX-clean where %ld is expected.  Thus, in places where such 64-bit
>  * variables are processed we let the compiler build the actual format
>  * using the GMT_LL string which is either "l" or "ll"
>  */
> #ifdef _WIN64
> typedef __int64 GMT_LONG;    /* A signed 8-byte integer under 64-bit 
> Windows */
> #define GMT_LL "ll"
> #else
> typedef long GMT_LONG;        /* A signed 4 (or 8-byte for 64-bit) 
> integer */
> #define GMT_LL "l"
> #endif
>
>
> than we use it for example like
>
>     sscanf (p, "%" GMT_LL "d-%" GMT_LL "d", &start, &stop);
>
>
> Excuse if this trivia for you guys (it wasn't for us)

Joaquim,

Have taken a look at this ticket and discussions?

http://trac.osgeo.org/gdal/ticket/2649

How 64 bit ints are handled in windows depend on which runtime libs are 
used.

Best regards,

Ari

>
> Joaquim Luis
>
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