Listing probe alias resolution failures

[David Smith]

Frank Ch. Eigler wrote:
> Hi -
> 
>> [...]
>> Ah, I see something I missed before with the following:
>> # stap -p2 -e 'probe vm.mmap ? { printf("%p %d\n", address, length) }'
>> [...]
>> probe vm.mmap = kernel.function("do_mmap"), kernel.function("do_mmap2")? {
>>     address = $addr
>>     length = $len
>> }
>> [...]
>> I missed the fact that the first one isn't optional.  But, shouldn't 
>> making 'vm.mmap' optional basically make 'kernel.function("do_mmap")' 
>> optional?
> 
> But "do_mmap" is found, and so the optional flag is satisfied.  The
> probe handler is processed without further error suppression.  It's
> not obvious that this is wrong. 

I guess I was thinking that the "optionalness" of vm.mmap would have 
meant that when do_mmap wasn't found, vm.mmap would be tossed (so that 
there would be no attempt to look up $addr and $len)

Perhaps the real bug is that the kernel.function("do_mmap") should be 
made optional in the vm.mmap probe alias.

-- 
David Smith
dsmith@redhat.com
Red Hat
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