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

[Eduard Zingerman <eddyz87@gmail.com>]

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