bug in objc_alignof_type

[Frederic De Jaeger]

Hi list,

I'm using :
Reading specs from /usr/lib/gcc-lib/i386-linux/3.2.3/specs
Configured with: ../src/configure -v 
--enable-languages=c,c++,java,f77,proto,pascal,objc,ada --prefix=/usr 
--mandir=/usr/share/man --infodir=/usr/share/info 
--with-gxx-include-dir=/usr/include/c++/3.2 --enable-shared --with-system-zlib 
--enable-nls --without-included-gettext --enable-__cxa_atexit 
--enable-clocale=gnu --enable-java-gc=boehm --enable-objc-gc i386-linux
Thread model: posix
gcc version 3.2.3 20030309 (Debian prerelease)

on an i386.

Consider this C type

typedef struct 
{
    int (indexSystem); 
    int (indexPort); 
    int (eliteRank); 
    double (money); 
    double (date); 
    NSString *(nameShip); 
    NSString *(stationName); 
    id (dicoShip); 
    BOOL (finish);
}(Contract);

apparently, the field "money" is aligned on a word.  Here, its offset
is 12 in the record.
In various place of gnustep base, the offset is computed using
objc_alignof_type.  For example, this is a piece of code from NSArchiver.m

[...]
          for (;;)
            {
              (*_eValImp)(self, eValSel, type, (char*)buf + offset);
              offset += objc_sizeof_type(type);
              type = objc_skip_typespec(type);
              if (*type == _C_STRUCT_E)
                {
                  break;
                }
              else
                {
!                 int   align = objc_alignof_type(type);
!                 int   rem = offset % align;
!
!                 if (rem != 0)
!                   {
!                     offset += align - rem;
!                   }
!               }
            }
[...]
In the case of the double type, objc_alignof_type answers 8.  Thus,
the result of that computation is that offset is incremented by 4 in
order to align on double word boundary.  Offset will be set to 16
instead of 12, with all the funny consequences.

Apparently, it looks like a bug of gcc. Does it ?

Cheers,

 Frédéric De Jaeger