netdev - [PATCH 3/7] libbpf: Return const btf_enum from btf

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Date:   Fri,  6 Sep 2019 09:31:40 +0200
From:   Jiri Olsa <jolsa@...nel.org>
To:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Andrii Nakryiko <andriin@...com>, Yonghong Song <yhs@...com>,
        Martin KaFai Lau <kafai@...com>
Subject: [PATCH 3/7] libbpf: Return const btf_enum from btf_enum inline function

I'm getting following errors when compiling with -Wcast-qual:

  bpf/btf.h: In function ‘btf_enum* btf_enum(const btf_type*)’:
  bpf/btf.h:259:34: warning: cast from type ‘const btf_type*’ to type
  ‘btf_enum*’ casts away qualifier
    259 |  return (struct btf_enum *)(t + 1);
        |                                  ^

The argument is const so the cast to following struct btf_enum
pointer should be const as well. Casting the const away in btf.c
call where it's correctly used without const in deduplication
code.

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/lib/bpf/btf.c | 2 +-
 tools/lib/bpf/btf.h | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index d6327bcc713a..5a39e9506760 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1475,7 +1475,7 @@ static int btf_for_each_str_off(struct btf_dedup *d, str_off_fn_t fn, void *ctx)
 			break;
 		}
 		case BTF_KIND_ENUM: {
-			struct btf_enum *m = btf_enum(t);
+			struct btf_enum *m = (struct btf_enum *) btf_enum(t);
 			__u16 vlen = btf_vlen(t);
 
 			for (j = 0; j < vlen; j++) {
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 6bbf5772aa61..3b3216fa348f 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -254,9 +254,9 @@ static inline const struct btf_array *btf_array(const struct btf_type *t)
 	return (const struct btf_array *)(t + 1);
 }
 
-static inline struct btf_enum *btf_enum(const struct btf_type *t)
+static inline const struct btf_enum *btf_enum(const struct btf_type *t)
 {
-	return (struct btf_enum *)(t + 1);
+	return (const struct btf_enum *)(t + 1);
 }
 
 static inline struct btf_member *btf_members(const struct btf_type *t)
-- 
2.21.0