Re: [DTrace-devel] [PATCH 2/4] Eliminate DT_VERS_LATEST

[Kris Van Hees <kris.van.hees@oracle.com>]

There is some overlap with the patch that follows this one, and that got me
thinking a bit more...

I think that we should rework all this a little bit, and have dt_version.h be
the sole source of version number data.  We can put macros in there that
provide all the version information (strings and codes), and use that to
populate everything else, I think.  That way we reduce the places where changes
need to be made (somewhat).

Let me muse on that a little and I'll follow-up with another email soon with
a example of what I am envisioing.

On Thu, Feb 27, 2025 at 11:40:45AM -0500, Kris Van Hees via DTrace-devel wrote:
> On Sat, Feb 08, 2025 at 02:06:20PM -0500, eugene.loh@oracle.com wrote:
> > From: Eugene Loh <eugene.loh@oracle.com>
> > 
> > Updating the DTrace version number requires too many distinct
> > changes.  Eliminate DT_VERS_LATEST, since it can be determined
> > on the fly.
> > 
> > Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
> > ---
> >  libdtrace/dt_open.c    |  3 ++-
> >  libdtrace/dt_version.h | 14 +++++---------
> >  2 files changed, 7 insertions(+), 10 deletions(-)
> > 
> > diff --git a/libdtrace/dt_open.c b/libdtrace/dt_open.c
> > index a02058871..b4d160359 100644
> > --- a/libdtrace/dt_open.c
> > +++ b/libdtrace/dt_open.c
> > @@ -721,7 +721,8 @@ dt_vopen(int version, int flags, int *errp,
> >  	dtp->dt_proc_fd = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK);
> >  	if (dt_aggregate_init(dtp) == -1)
> >  		return set_open_errno(dtp, errp, dtrace_errno(dtp));
> > -	dtp->dt_vmax = DT_VERS_LATEST;
> > +	for (i = 0; _dtrace_versions[i] != 0; i++)
> > +		dtp->dt_vmax = _dtrace_versions[i];
> 
> dtp->dt_vmax = _dtrace_versions[ARRAY_SIZE(_dtrace_versions) - 2];
> 
> (-2 to account for the 0 sentinel value)
> 
> But this will only be accurate if you also add 2.0.1 to the _dtrace_versions
> array, and then you should probably add 2.0.2 to it also for accuracy.
> 
> >  	dtp->dt_cpp_path = strdup(_dtrace_defcpp);
> >  	dtp->dt_cpp_argv = malloc(sizeof(char *));
> >  	dtp->dt_cpp_argc = 1;
> > diff --git a/libdtrace/dt_version.h b/libdtrace/dt_version.h
> > index 3fd1b3d1e..bef3243e9 100644
> > --- a/libdtrace/dt_version.h
> > +++ b/libdtrace/dt_version.h
> > @@ -38,18 +38,15 @@ extern "C" {
> >   *
> >   * These #defines are used in identifier tables to fill in the version fields
> >   * associated with each identifier.  The DT_VERS_* macros declare the encoded
> > - * integer values of all versions used so far.  DT_VERS_LATEST must correspond
> > - * to the latest version value among all versions exported by the D compiler.
> > - * DT_VERS_STRING must be an ASCII string that contains DT_VERS_LATEST within
> > - * it along with any suffixes (e.g. Beta).
> > + * integer values of all versions used so far.  DT_VERS_STRING must be an ASCII
> > + * string that contains the latest version within it along with any suffixes
> > + * (e.g. Beta).  You must update DT_VERS_STRING when adding a new version,
> > + * and then add the new version to the _dtrace_versions[] array declared in
> > + * dt_open.c.
> >   *
> >   * Refer to the Solaris Dynamic Tracing Guide Versioning chapter for an
> >   * explanation of these DTrace features and their values.
> >   *
> > - * You must update DT_VERS_LATEST and DT_VERS_STRING when adding a new version,
> > - * and then add the new version to the _dtrace_versions[] array declared in
> > - * dt_open.c..
> > - *
> >   * NOTE: Although the DTrace versioning scheme supports the labeling and
> >   *       introduction of incompatible changes (e.g. dropping an interface in a
> >   *       major release), the libdtrace code does not currently support this.
> > @@ -85,7 +82,6 @@ extern "C" {
> >  #define	DT_VERS_2_0	DT_VERSION_NUMBER(2, 0, 0)
> >  #define	DT_VERS_2_0_1	DT_VERSION_NUMBER(2, 0, 1)
> >  
> > -#define	DT_VERS_LATEST	DT_VERS_2_0_1
> >  #define	DT_VERS_STRING	"Oracle D 2.0"
> 
> You should add 2.0.2 and update the DT_VERS_STRING also.
> 
> >  
> >  #ifdef  __cplusplus
> > -- 
> > 2.43.5
> > 
> 
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