netdev - [PATCH 4/7] libbpf: Return const btf_member from btf

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Date:   Fri,  6 Sep 2019 09:31:41 +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 4/7] libbpf: Return const btf_member from btf_members inline function

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

  bpf/btf.h: In function ‘btf_member* btf_members(const btf_type*)’:
  bpf/btf.h:264:36: warning: cast from type ‘const btf_type*’ to type
  ‘btf_member*’ casts away qualifiers [-Wcast-qual]
    264 |  return (struct btf_member *)(t + 1);
        |                                    ^

The argument is const so the cast to following struct btf_member
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    | 4 ++--
 tools/lib/bpf/btf.h    | 4 ++--
 tools/lib/bpf/libbpf.c | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 5a39e9506760..560d1ae33675 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -1463,7 +1463,7 @@ static int btf_for_each_str_off(struct btf_dedup *d, str_off_fn_t fn, void *ctx)
 		switch (btf_kind(t)) {
 		case BTF_KIND_STRUCT:
 		case BTF_KIND_UNION: {
-			struct btf_member *m = btf_members(t);
+			struct btf_member *m = (struct btf_member *) btf_members(t);
 			__u16 vlen = btf_vlen(t);
 
 			for (j = 0; j < vlen; j++) {
@@ -2797,7 +2797,7 @@ static int btf_dedup_remap_type(struct btf_dedup *d, __u32 type_id)
 
 	case BTF_KIND_STRUCT:
 	case BTF_KIND_UNION: {
-		struct btf_member *member = btf_members(t);
+		struct btf_member *member = (struct btf_member *) btf_members(t);
 		__u16 vlen = btf_vlen(t);
 
 		for (i = 0; i < vlen; i++) {
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 3b3216fa348f..cd1bd018ba8b 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -259,9 +259,9 @@ static inline const struct btf_enum *btf_enum(const struct btf_type *t)
 	return (const struct btf_enum *)(t + 1);
 }
 
-static inline struct btf_member *btf_members(const struct btf_type *t)
+static inline const struct btf_member *btf_members(const struct btf_type *t)
 {
-	return (struct btf_member *)(t + 1);
+	return (const struct btf_member *)(t + 1);
 }
 
 /* Get bit offset of a member with specified index. */
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 2233f919dd88..7d3d6284dd2e 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -1389,7 +1389,7 @@ static void bpf_object__sanitize_btf(struct bpf_object *obj)
 		} else if (!has_datasec && btf_is_datasec(t)) {
 			/* replace DATASEC with STRUCT */
 			const struct btf_var_secinfo *v = btf_var_secinfos(t);
-			struct btf_member *m = btf_members(t);
+			struct btf_member *m = (struct btf_member *) btf_members(t);
 			struct btf_type *vt;
 			char *name;
 
-- 
2.21.0