[PATCH dwarves v2 1/5] fprintf: Correct names for types with btf_type_tag attribute

Eduard Zingerman
2023-03-14T23:04:37Z

The following example contains a structure field annotated with
btf_type_tag attribute:

#define __tag1 __attribute__((btf_type_tag("tag1")))

struct st {
int __tag1 *a;
} g;

It is not printed correctly by `pahole -F dwarf` command:

$ clang -g -c test.c -o test.o
pahole -F dwarf test.o
struct st {
tag1 * a; /* 0 8 */
...
};

Note the type for variable `a`: `tag1` is printed instead of `int`.
This commit teaches `type__fprintf()` and `__tag_name()` logic to skip
`DW_TAG_LLVM_annotation` objects that are used to encode type tags.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
dwarves_fprintf.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/dwarves_fprintf.c b/dwarves_fprintf.c
index e8399e7..1e6147a 100644
--- a/dwarves_fprintf.c
+++ b/dwarves_fprintf.c
@@ -572,6 +572,7 @@ static const char *__tag__name(const struct tag *tag, const struct cu *cu,
case DW_TAG_restrict_type:
case DW_TAG_atomic_type:
case DW_TAG_unspecified_type:
+ case DW_TAG_LLVM_annotation:
type = cu__type(cu, tag->type);
if (type == NULL && tag->type != 0)
tag__id_not_found_snprintf(bf, len, tag->type);
@@ -786,6 +787,10 @@ next_type:
n = tag__has_type_loop(type, ptype, NULL, 0, fp);
if (n)
return printed + n;
+ if (ptype->tag == DW_TAG_LLVM_annotation) {
+ type = ptype;
+ goto next_type;
+ }
if (ptype->tag == DW_TAG_subroutine_type) {
printed += ftype__fprintf(tag__ftype(ptype),
cu, name, 0, 1,
@@ -880,6 +885,14 @@ print_modifier: {
else
printed += enumeration__fprintf(type, &tconf, fp);
break;
+ case DW_TAG_LLVM_annotation: {
+ struct tag *ttype = cu__type(cu, type->type);
+ if (ttype) {
+ type = ttype;
+ goto next_type;
+ }
+ goto out_type_not_found;
+ }
}
out:
if (type_expanded)
--
2.39.1