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Old 11-26-2005, 05:23 AM   #1
kpachopoulos
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include/linux/types.h and include/linux/posix_types.h


include/linux/types.h
Code:
20 typedef __kernel_fd_set         fd_set;
21 typedef __kernel_dev_t          dev_t;
.......
32 typedef __kernel_mqd_t          mqd_t;
include/linux/posix_types.h
Code:
36 typedef struct {
37         unsigned long fds_bits [__FDSET_LONGS];
38 } __kernel_fd_set;
Why don't we use __kernel_fd_set directly?
What more does "typedef __kernel_fd_set fd_set;" offer us?
This applies to most typedef's in include/linux/types.h; this is just an example.
Thanks
 
Old 11-26-2005, 05:38 AM   #2
Nylex
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A typedef basically lets you have an alias for something. By using fd_set, you still are using __kernel_fd_set directly, it's just that you have less to type.

Edit: this is what I know about typedef generally, from my knowledge of C++. I hope this is right!
 
Old 11-26-2005, 05:52 AM   #3
kpachopoulos
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You're right Nylex, but why not write:
Code:
36 typedef struct {
37         unsigned long fds_bits [__FDSET_LONGS];
38 } kernel_fd_set;
instead of

Code:
36 typedef struct {
37         unsigned long fds_bits [__FDSET_LONGS];
38 }__kernel_fd_set;
?
 
  


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