> Daniel Alley wrote:
> 
> But it can be in the function CALLING such a function, and said function 
> will be completely missing from the backtrace.
> 
> Quoting your link 
> [https://developer.arm.com/documentation/dui0774/k/Compiler-Command-line-O...]:

The quotation says the opposite of what you are saying.  "leaves the frame 
pointer pointing to the caller's frame"  => the caller set the frame pointer, 
the leaf did not, therefore the leaf function will not show up but the caller 
still will.  

> And that limitation makes -fno-omit-frame-pointer useless for the purpose 
> for which it is being forced onto Fedora users.
>
> The other limitation that I have mentioned is also documented there:
> 
> That, too, means frame pointers cannot by design solve the problem which the 
> change intends to solve with them.
> 
>         Kevin Kofler

You seem to be arguing that because the solution is not 100% perfect (and it 
was already acknowledged that it is not), it is useless.  

Is shipping debug symbols for an optimized binary completely useless just 
because there are situations where optimizations like inlining and TCO make the 
executed code radically different from the source code, and therefore make it 
impossible to trace the execution line by line?

I don't work at Facebook and I have no idea how Facebook do things, but I _very 
strongly doubt_ that they are disabling all those optimizations in their 
binaries for the sake of perfect unwinding behavior, and yet despite this they 
claim to have realized a lot of value from this change.  If you want to claim 
that this is "useless", then you are also claiming that any benefit which has 
already been realized by using it is retroactively invalid.
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