[DTrace-devel] [PATCH 03/20] Do not print an offset for builtin variables

[Kris Van Hees]

On Wed, Jun 09, 2021 at 11:27:15AM -0400, Eugene Loh wrote:
> Actually, speaking of testing, how does this patch do with the test 
> suite?  It seems to me that it causes 
> test/unittest/variables/gvar/tst.undecl-offset.sh to FAIL.

Well, no, it wouldn't in its new version (i.e. the version that contains your
reviewed-by and adds a test as you requested, and that also got updated of
course in view of earlier patches being affected by it).

I just can't put it on the -dev tree yet because I am still waiting for your
review of "[02/20] Fix alignment of global and local variables".

> On 6/2/21 1:38 PM, Eugene Loh wrote:
> > Reviewed-by: Eugene Loh <eugene.loh at oracle.com>
> > though it would be nice to have tests accompany patches.
> >
> > On 6/2/21 1:47 AM, Kris Van Hees wrote:
> >> Builtin variables are global variables but their value is not stored
> >> in the gvars BPF map.  Therefore, their offset is always -1 which is
> >> displayed as ffffffff.  That value is too wide for the OFFSET field
> >> in the variable list in the disassembly listing.  Since the offset
> >> value is not meaningful in this case, it is no longer printed.
> >>
> >> Offsets are now also printed in decimal rather than hexadecimal to be
> >> consistent with other offset values in disassembly listings.
> >>
> >> Signed-off-by: Kris Van Hees <kris.van.hees at oracle.com>
> >> ---
> >>   libdtrace/dt_dis.c | 10 +++++++---
> >>   1 file changed, 7 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/libdtrace/dt_dis.c b/libdtrace/dt_dis.c
> >> index a8c4e1ca..fdd10dc3 100644
> >> --- a/libdtrace/dt_dis.c
> >> +++ b/libdtrace/dt_dis.c
> >> @@ -716,7 +716,11 @@ dt_dis_difo(const dtrace_difo_t *dp, FILE *fp, 
> >> const dt_ident_t *idp,
> >>         for (i = 0; i < dp->dtdo_varlen; i++) {
> >>           dtrace_difv_t *v = &dp->dtdo_vartab[i];
> >> -        char kind[4], scope[4], range[12], flags[16] = { 0 };
> >> +        char offset[11] = { 0 }, flags[16] = { 0 };
> >> +        char kind[4], scope[4], range[12];
> >> +
> >> +        if (v->dtdv_offset != -1)
> >> +            snprintf(offset, sizeof(offset), "%u", v->dtdv_offset);
> >>             switch (v->dtdv_kind) {
> >>           case DIFV_KIND_AGGREGATE:
> >> @@ -759,9 +763,9 @@ dt_dis_difo(const dtrace_difo_t *dp, FILE *fp, 
> >> const dt_ident_t *idp,
> >>           if (v->dtdv_flags & DIFV_F_MOD)
> >>               strcat(flags, "/w");
> >>   -        fprintf(fp, "%-16s %-4x %-6x %-3s %-3s %-11s %-4s %s\n",
> >> +        fprintf(fp, "%-16s %-4x %-6s %-3s %-3s %-11s %-4s %s\n",
> >>               &dp->dtdo_strtab[v->dtdv_name], v->dtdv_id,
> >> -            v->dtdv_offset, kind, scope, range, flags + 1,
> >> +            offset, kind, scope, range, flags + 1,
> >>               dt_dis_typestr(&v->dtdv_type, type, sizeof(type)));
> >>       }
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