* Segher Boessenkool:

On Tue, Sep 06, 2022 at 02:37:47PM +0200, Florian Weimer wrote:

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On Mon, Aug 22, 2022 at 4:01 PM Florian Weimer [off-list ref] wrote:
I did some research on the 'sibcalls' you mentioned above. Feel like
It's a little similar to 'inline', and makes the callee use the same stack
frame with the caller, which obviously will influence the result of
'__builtin_return_address'.

Sibling calls are essentially calls that can be replaced by jumps (aka
"tail call"), without needing a separate entry point to the callee.

Different targets can have a slightly different implementation and
definition of what exactly is a sibling call, but that's the gist.

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Hmm......but I'm not able to find any attribute to disable this optimization.
Do you have any ideas?

Unless something changed quite recently, GCC does not allow disabling
the optimization with a simple attribute (which would have to apply to
function pointers as well, not functions).

It isn't specified what a sibling call exactly *is*, certainly not on C
level (only in the generated machine code), and the details differs per
target.

Sure, but GCC already disables this optimization in a generic fashion
for noreturn calls.  It should be possible to do the same based another
function attribute.

Thanks,
Florian