Different types for zero length bit fields in c? -

Different types for zero length bit fields in c? -

fount statement a zero-width bit field can cause next field aligned on next container boundary container same size underlying type of bit field

to set practice assuming int 2 bytes (16 bits) , short 1 byte (8 bits) save typing. let's using gcc compiler (would nice explain differences clang).

struct foo { unsigned int a:5; unsigned int :0; unsigned int b:3; }

in memory looks

struct address | | v aaaaa000 00000000 bbb00000 00000000

question 1: in understanding can not aaaaa000 00000000 0..00bbb00000..., bbb has align container directly next current container. true?

moving on, if specify

struct bar { unsigned short x:5; unsigned int :0; unsigned short y:7; }

will so?

struct address | short stops here short starts | | | v v | uint | v xxxxx000 00000000 00000000 yyyyyyy0

edit 1 pointed out short can not less 16 bytes. beside point in question. if of import you can replace short char , int short

update, after reading text in context:

the result of illustration (corrected utilize char):

struct bar { unsigned char x:5; unsigned int :0; unsigned char y:7; }

would (assuming 16-bit int):

char pad pad int boundary | | | | v v v v xxxxx000 00000000 yyyyyyy0

(i'm ignoring endian).

the zero-length bitfield causes position move next int boundary. defined int 16-bit, 16 minus 5 gives 11 bits of padding.

it not insert entire blank int. illustration on page link demonstrates (but using 32-bit integers).

c bit-fields