Re: [PATCH] memory: Replace DEBUG_UNASSIGNED printf calls by trace events

[Eric Blake <eblake@redhat.com>]

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On 9/20/19 9:39 AM, Philippe Mathieu-Daudé wrote:

>>> I thought I read a comment about it between Eric/Stefan but I can't find
>>> it, maybe I dreamed it. (Cc'ed Eric).

Not from me.  But looking at scripts/tracetool/format/log_stap.py, I
suspect the dtrace via stap backend cannot support it.

Researching further,

https://sourceware.org/systemtap/langref.pdf

section 9.2 printf, states:

"The printf formatting directives are similar to those of C, except that
they are fully checked for type by the translator."

and does NOT list handling for '*' under precision or width.


>>
>> If my grep is correct we currently use the syntax already in
>> gt64120_read, gt64120_write, pflash_io_read, pflash_io_write,
>> pflash_data_read and pflash_data_write trace events.
> 
> If you use 'git blame' you'll notice I added all of them, so better
> let's get a proper confirmation from Stefan :)
> 
> I plan to use them more, I find them helpful to directly see the access
> size looking at the value width.

You'll probably have to revert that, or else teach the various backend
generators how to dumb-down a format string containing it when coupled
with a backend that doesn't support it natively.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org


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