Mon Jan 21 18:31:00 GMT 2008
The code that uses HAVE_DD_LOCK in libc/posix was taken from an existing
code base (IIRC FreeBSD).
The code in libc/posix is offered optionally to platforms. The dir
family routines code there can be ignored if the platform already
supplies these functions (via the flag HAVE_OPENDIR). If not
short-circuited via HAVE_OPENDIR, a port must implement sys/dirent.h or
else the code will not build to begin with as you are probably already
well-aware. A platform can also build these and also override them in
either the libc/machine/xxx or libc/sys/xxxx directories.
So, if you choose to build the functions in libc/posix for your platform
and you do not short-circuit them with HAVE_OPENDIR and do not override
them yourself in your libc/sys directory and you support
multi-threading, then you had either better implement the dd_lock field
and set HAVE_DD_LOCK or else document that those functions are not
-- Jeff J.
Neal H. Walfield wrote:
> I'm trying to understand the purpose of HAVE_DD_LOCK. It seems to me
> either the library is multi-threaded, in which case the locking
> functionality described in libc/include/sys/lock.h must be provided
> and not locking is a bug, or the library is single-threaded, in which
> case, the locking primitives a no-ops.
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