about -funsigned-bitfields

[chenghuiming_bjgmail]

the document said that -funsigned-bitfieldsDetermines whether the default bitfield type is changed tounsigned. but what is default bitfield type?

thanks in advance.

[Om_S_Intel]

By default it is treated as signed int but this may be changed by the -funsigned-bitfields option.

You may learn more on it by following http://gcc.gnu.org/onlinedocs/gcc/Structures-unions-enumerations-and-bit_002dfields-implementation.html

[Feilong_H_Intel]

Hi there,

The default bitfield type signed. Gcc manual gives more details below.

----------
-fsigned-bitfields

-funsigned-bitfields

-fno-signed-bitfields

-fno-unsigned-bitfields

These options control whether a bit-field is signed or unsigned, when the declaration does not use either signed or unsigned. By default, such a bit-field is signed, because this is consistent: the basic integer types such as int are signed types.
----------

Thanks,
Feilong

[chenghuiming_bjgmail]

Thank all.

I got it.

a.c:

struct node

{

int a:2; //no unsigned or signed before int

};

if compiled by icc -funsigned-bitfieds a.c , field a is unsigned int .

if compiled by icc a.c, field a is signed int.