Hi -

> [...]
> - It _does not_ change the compiler optimisations.

Like any similar mechanism, it does force the compiler to change its
code generation, so one can't claim this too strongly.

> [...]  Comments are welcome,

I'm still uneasy about the use of varargs.  The current code now uses
the formatting string as metadata to be matched (strcmp) between
producer and consumer.  A general tool that would use them would have
to start parsing general printf directives.  I believe they are not
quite general enough either e.g. to describe a raw binary blob.

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).  But maybe there is a better way.

Also, while regparm(0) may provide some comfort on x86, is there good
reason to believe that the same trick works (and will continue to
work) on non-x86 platforms to invoke a non-varargs callee with a
varargs caller?


- FChE