netdev - Re: [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 18:27:06 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     netdev@...r.kernel.org, Alexei Starovoitov <ast@...com>,
        Daniel Borkmann <daniel@...earbox.net>, kernel-team@...com
Subject: Re: [PATCH bpf-next 1/2] tools/bpf: add const qualifier to
 btf__get_map_kv_tids() map_name parameter

On Tue, Feb 05, 2019 at 11:48:22AM -0800, Yonghong Song wrote:
> 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>

Acked-by: Alexei Starovoitov <ast@...nel.org>