On Fri, 12 Feb 2010, Joakim Tjernlund wrote: > Wolfgang Denk <w...@denx.de> wrote on 2010/02/11 22:39:00: > > Dear Joakim Tjernlund, > > > > In message <OF918AA866.3ED427EB-ONC12576C7.005CBEE4-C12576C7. > > 005cf...@transmode.se> you wrote: > > > > > > > I have no idea how it is actually done in the kernel code... but gcc > > > > defines it: > > > > > > > > gcc -dM -E -x c - <<<'' | grep ENDIAN > > > > #define __BIG_ENDIAN__ 1 > > > > #define _BIG_ENDIAN 1 > > > > > > That doesn't define __BYTE_ORDER. Try the same gcc command > > > on a file that #includes <stdlib.h> and you will get both > > > __BIG_ENDIAN and __LITTLE_ENDIAN > > > > For me this appears to work: > > > > On x86: > > > > $ echo '#include <stdlib.h>' | gcc -dM -E -x c - | grep ENDIAN > > #define _ENDIAN_H 1 > > #define PDP_ENDIAN __PDP_ENDIAN > > #define __PDP_ENDIAN 3412 > > #define BIG_ENDIAN __BIG_ENDIAN > > #define __BYTE_ORDER __LITTLE_ENDIAN > > #define __LITTLE_ENDIAN 1234 > > #define __BIG_ENDIAN 4321 > > #define LITTLE_ENDIAN __LITTLE_ENDIAN > > > > On PowerPC: > > > > $ echo '#include <stdlib.h>' | gcc -dM -E -x c - | grep ENDIAN > > #define __BIG_ENDIAN__ 1 > > #define __PDP_ENDIAN 3412 > > #define __LITTLE_ENDIAN 1234 > > #define BIG_ENDIAN __BIG_ENDIAN > > #define _BIG_ENDIAN 1 > > #define __BYTE_ORDER __BIG_ENDIAN > > #define _ENDIAN_H 1 > > #define __BIG_ENDIAN 4321 > > #define PDP_ENDIAN __PDP_ENDIAN > > #define LITTLE_ENDIAN __LITTLE_ENDIAN > > > > In both cases __BYTE_ORDER is set to a sane value. > > Yes, but that was not what I meant. If you look closer you see that both > __BIG_ENDIAN and __LITTLE_ENDIAN are defined in each compiler. This means > you cannot use these two defines directly to tell if your arch is BE or LE.
The proper tests are: - #if __BYTE_ORDER == __BIG_ENDIAN - #if __BYTE_ORDER == __LITTLE_ENDIAN i.e. don't just test for the presence of __BIG_ENDIAN or __LITTLE_ENDIAN. With kind regards, Geert Uytterhoeven Software Architect Techsoft Centre Technology and Software Centre Europe The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium Phone: +32 (0)2 700 8453 Fax: +32 (0)2 700 8622 E-mail: geert.uytterhoe...@sonycom.com Internet: http://www.sony-europe.com/ A division of Sony Europe (Belgium) N.V. VAT BE 0413.825.160 · RPR Brussels Fortis · BIC GEBABEBB · IBAN BE41293037680010 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
