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

[Eugene Loh]

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)));
>   	}
>