Messages in this thread | | | Subject | Re: [PATCH] Linux Kernel Markers 0.11 for 2.6.17 | From | (Frank Ch. Eigler) | Date | 26 Sep 2006 12:39:38 -0400 |
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Mathieu Desnoyers <compudj@krystal.dyndns.org> writes:
> [...] > > I believe [printf formatting directives] are not > > quite general enough either e.g. to describe a raw binary blob. > > If you want to dump a raw binary blob, what about : > MARK(mysubsys_myevent, "char %p %u", blobptr, blobsize); where %p is > a pointer to an array of char and %u the length ?
That involves new conventions beyond printf. Why not "%p %p %u %u" for two blobs ... or why implicitly dereference the given pointers. A probe handler unaware of a specific marker's semantics would not know whether or not this is implied.
> My idea is to use the string to identify what is referred by a > pointer, so it can be casted into this type with some kind of > coherency between the marker and the probe.
I understand what you're using them for. To me, they just don't look like a good fit.
> > I realize they serve a useful purpose in abbreviating what otherwise > > one might have to do (like that multiplicity of STAP_MARK_* type/arity > > permutations). [...] > > I think that duplicating the number of marker macros could easily make > them unflexible and ugly. [...]
Inflexible and ugly in what way? Remember, the macro definitions can be automatically generated. At the macro call site, there needs to be little difference.
> [...] Good point, I will setup a va_args in the probe. When > correctly used, however, there is no need to use the format string : > we can directly get the variables from the var arg list if we know > in advance what the string will be.
Do I understand you correctly that the probe handlers would be given va_list values, and would have to call va_arg to yank out individual actual arguments? So again type safety is a matter of explicit coding (equivalent to correctly casting each type)?
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