Possible Duplicate:
what does this mean in c int a:16; ?
What does the :1 mean here:
...
unsigned respawn:1;
unsigned just_respawn:1;
unsigned detached:1;
unsigned exiting:1;
unsigned exited:1;
} ngx_process_t;
Asked
Active
Viewed 287 times
3
Community
- 1
- 1
compile-fan
- 16,885
- 22
- 59
- 73
-
1Many duplicates on SO already, e.g. [what does this mean in c int a:16; ?](http://stackoverflow.com/questions/4706584/what-does-this-mean-in-c-int-a16); [Colons after variable name on C code.](http://stackoverflow.com/questions/3983943/colons-after-variable-name-on-c-code); [What does 'unsigned temp:3' means](http://stackoverflow.com/questions/2950029/what-does-unsigned-temp3-means). – Paul R May 25 '11 at 12:49
2 Answers
5
This looks like a bit field in a struct (the header you omitted). The :1 means "1 bit wide", so in your case, they're all booleans. The compiler is supposed to optimize their space usage by packing many of them per byte.
JB.
- 40,344
- 12
- 79
- 106
-
-
@compile-fan: it's the field's type. Fields are integers, they can be either signed or unsigned. (this would mostly make sense for fields wider than 1). – JB. May 25 '11 at 13:14
3
respawn is a bitfield which is 1 bit wide, so it can take on the value of 0 or 1.
Ferruccio
- 98,941
- 38
- 226
- 299
-
-
bit-fields, like ints, can be signed or unsigned. In the case of a 1-bit field, you want it to be unsigned because you don't have room for a sign bit. – Ferruccio May 25 '11 at 12:57
-
Actually, I suppose you could have a signed int bit field which is 1 bit wide. It could store either a -1 or 0. – Ferruccio Feb 06 '13 at 13:12