netdev - [PATCH bpf-next 1/2] tools/bpf: add const qualifier to btf__get_map_kv_tids() map

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Date:   Tue, 5 Feb 2019 11:48:22 -0800
From:   Yonghong Song <yhs@...com>
To:     <netdev@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>,
        Yonghong Song <yhs@...com>
Subject: [PATCH bpf-next 1/2] tools/bpf: add const qualifier to btf__get_map_kv_tids() map_name parameter

Commit 96408c43447a ("tools/bpf: implement libbpf btf__get_map_kv_tids() API function")
added the API function btf__get_map_kv_tids():
  btf__get_map_kv_tids(const struct btf *btf, char *map_name, ...)

The parameter map_name has type "char *". This is okay inside libbpf library since
the map_name is from bpf_map->name which also has type "char *".

This will be problematic if the caller for map_name already has attribute "const",
e.g., from C++ string.c_str(). It will result in either a warning or an error.

  /home/yhs/work/bcc/src/cc/btf.cc:166:51:
    error: invalid conversion from ‘const char*’ to ‘char*’ [-fpermissive]
      return btf__get_map_kv_tids(btf_, map_name.c_str()

This patch added "const" attributes to map_name parameter.

Fixes: 96408c43447a ("tools/bpf: implement libbpf btf__get_map_kv_tids() API function")
Signed-off-by: Yonghong Song <yhs@...com>
---
 tools/lib/bpf/btf.c | 2 +-
 tools/lib/bpf/btf.h | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 4949f8840bda..3b3a2959d03a 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -511,7 +511,7 @@ int btf__get_from_id(__u32 id, struct btf **btf)
 	return err;
 }
 
-int btf__get_map_kv_tids(const struct btf *btf, char *map_name,
+int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
 			 __u32 expected_key_size, __u32 expected_value_size,
 			 __u32 *key_type_id, __u32 *value_type_id)
 {
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 25a9d2db035d..b393da90cc85 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -69,7 +69,7 @@ LIBBPF_API void btf__get_strings(const struct btf *btf, const char **strings,
 				 __u32 *str_len);
 LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset);
 LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf);
-LIBBPF_API int btf__get_map_kv_tids(const struct btf *btf, char *map_name,
+LIBBPF_API int btf__get_map_kv_tids(const struct btf *btf, const char *map_name,
 				    __u32 expected_key_size,
 				    __u32 expected_value_size,
 				    __u32 *key_type_id, __u32 *value_type_id);
-- 
2.17.1