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Diffstat (limited to 'lib/libc/sys/dup.2')
| -rw-r--r-- | lib/libc/sys/dup.2 | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/lib/libc/sys/dup.2 b/lib/libc/sys/dup.2 index 8989639..29d1ada 100644 --- a/lib/libc/sys/dup.2 +++ b/lib/libc/sys/dup.2 @@ -95,6 +95,53 @@ is specified. If this descriptor is already in use, the descriptor is first deallocated as if a .Xr close 2 call had been done first. +.Sh IMPLEMENTATION NOTES +.Pp +In the non-threaded library +.Fn dup +is implemented as the +.Va dup +syscall. +.Pp +In the threaded library, the +.Va dup +syscall is assembled to +.Fn _thread_sys_dup +and +.Fn dup +is implemented as a function which locks +.Va oldd +for read and write, then calls +.Fn _thread_sys_dup . +Before returning, +.Fn dup +unlocks +.Va oldd . +.Pp +In the non-threaded library +.Fn dup2 +is implemented as the +.Va dup2 +syscall. +.Pp +In the threaded library, the +.Va dup2 +syscall is assembled to +.Fn _thread_sys_dup2 +and +.Fn dup2 +is implemented as a function which locks both +.Va oldd +and +.Va newd +for read and write, then calls +.Fn _thread_sys_dup2 . +Before returning, +.Fn dup2 +unlocks +.Va oldd . +and +.Va newd . .Sh RETURN VALUES The value -1 is returned if an error occurs in either call. The external variable |
