The precise meaning of talloc_tos()
obnox at samba.org
Sat Apr 7 17:35:48 MDT 2012
Richard Sharpe wrote:
> Hi folks,
> I noticed this comment in lib/util/talloc_stack.h
> * Implement a stack of talloc frames.
> * When a new talloc stackframe is allocated with talloc_stackframe(), then
> * the TALLOC_CTX returned with talloc_tos() is reset to that new
> * frame. Whenever that stack frame is TALLOC_FREE()'ed, then the reverse
> * happens: The previous talloc_tos() is restored.
> My question hinges around the use of the word reset above in "the
> TALLOC_CTX returned with talloc_tos() is *reset* to that new frame."
Maybe it should read "set" instead of "reset".
> I think that the code in talloc_stackframe.c shows that reset is the
> wrong word there and it simply returns the context associated with the
> current top of the talloc stack or a new one if no stack yet exists,
> however, given my recent demonstrated ability to mis-read code, can
> someone confirm :-)
talloc_tos / talloc_stackframe / talloc_free implements a stack
of talloc contexts. It is roughly meant to accompany the stack
of function calls to provide temporary memory for the function
* talloc_tos() always returns the current top of stack (tos)
* talloc_stackframe() creates a new talloc context and puts it
on top of the stack (and also returns the new context).
This means that the next call to talloc_tos() will return
this newly created context.
This is what is meant with "reset" in the comment quoted above.
* talloc_free() applied to the top of stack pops the context
off the stack, in partictular, it also so changes the value
of the next talloc_tos() call.
Does this help?
Cheers - Michael
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Size: 206 bytes
Desc: not available
More information about the samba-technical