Re: [PATCH-for-5.2 v2] trace: use STAP_SDT_V2 to work around symbol visibility

[Frank Ch. Eigler]

Hi -

> > Maybe add a comment? (no need to repost if you agree):
> >
> >        # Workaround to avoid dtrace(1) produces file with 'hidden'
> >        # symbol visibility, define STAP_SDT_V2 to produce 'default'
> >        # symbol visibility instead.
> >
> > > +    QEMU_CFLAGS="$QEMU_CFLAGS -DSTAP_SDT_V2"

Please note that we don't know how long this behavior will persist.
You are relying on an accident. :-)

Much of the systemtap code doesn't support real STAP_SDT_V2 format,
and /usr/include/sys/sdt.h cannot generate it at all.  That macro
tricks only the dtrace-header-generator to suppress the "hidden"
visibility attribute, but doesn't change probe metadata format to the
old V2 (in .probes sections rather than .note.* ELF notes).

We'll try not to break it, but please move toward the more proper
per-solib or per-executable hidden copies of the semaphore objects.

- FChE