Re: [ft-devel] freetype-2.3.7 -- ftconfig.h for biarch systems

[mpsuzuki]

On Tue, 8 Jul 2008 22:39:58 +0200
Antoine Leca <address@hidden> wrote:
>On Monday, June 30th, 2008, mpsuzuki wrote:
>> So, I think, using traditional ANSI C header "limits.h"
>> is more generic than using modern headers "bits/wordsize.h", like...
>>
>> #ifdef HAVE_LIMITS_H
>>
>> # if   ( UINT_MAX == 0xFFFFFFFFFFFFFFFF )
>> #  define FT_SIZEOF_INT 8
>> # elif ( UINT_MAX == 0xFFFFFFFFFFFF )
>> #  define FT_SIZEOF_INT 6
>> # elif ( UINT_MAX == 0xFFFFFFFF )
>> #  define FT_SIZEOF_INT 4
>> # else
>> #  error XXX
>> # endif
>
>There is a real defect with the above approach: imagine a conforming C90 
>compiler with 32 bits being the widest type; on such a compiler, cpp would 
>evaluate the quantities using 32-bit arithmetic; unsigned truncates, so 
>0xFFFFFFFFFFFFFFFF would truncate to 0xFFFFFFFF, perhaps with a warning but 
>this is not required; and the first test succeeds; of course, this is not 
>what you want!

Thank you, I happened to find the defect you wrote, during
the tests of Tiny C compiler and Bruce's C compiler. So
my revised proposal has the check of cpp feature:

        #if ( 0x7FFFFFFFUL < 0x7FFFFFFFFFFFFFFFUL )

        # warning cpp can evaluate 64bit numerics

        # if ( INT_MAX < 0x7FFF )
        #  error Non-standard C whose int cannot cover signed 16bit 
        # elif ( 0x7FFF <= INT_MAX ) && ( INT_MAX < 0x7FFFFFFFUL )
        #  define FT_SIZEOF_INT 2
        # elif ( 0x7FFFFFFF <= INT_MAX ) && ( INT_MAX < 0x7FFFFFFFFFFFUL )
        #  define FT_SIZEOF_INT 4
        # else
        #  define FT_SIZEOF_INT 8
        # endif

(http://lists.gnu.org/archive/html/freetype-devel/2008-07/msg00010.html).

The truncation (as a string process from the beginning)
of too long numerical constant is de-jure behaviour in C90?
I was misunderstanding that too long numerical constant
causes some overflow in cpp. Considering the possibility
of the string truncation from the end to fit 32bit integer,
should I check another possibility like following?

        # if ( 0x7FFFFFFFUL < 0x000000017FFFFFFFUL )

Regards,
mpsuzuki