linux-kernel - RE: [PATCH] bpf: bpftool: convert ‘const char *’ type into 'char *' in assignment

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Date:   Thu, 28 Mar 2019 15:08:49 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Quentin Monnet' <quentin.monnet@...ronome.com>,
        "ast@...nel.org" <ast@...nel.org>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "kafai@...com" <kafai@...com>,
        "songliubraving@...com" <songliubraving@...com>,
        "yhs@...com" <yhs@...com>,
        "jakub.kicinski@...ronome.com" <jakub.kicinski@...ronome.com>,
        "df@...gle.com" <df@...gle.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] bpf: bpftool: convert ‘const char *’ type into 'char *' in assignment

From: Quentin Monnet
> Sent: 28 March 2019 14:31
> 2019-03-28 10:16 UTC-0400 ~ Bo YU <tsu.yubo@...il.com>
> > When compiling with check flag: make -C tools/bpf/bpftool/
> > gcc will warning:
> >
> > jit_disasm.c:119:29: warning: assignment discards ‘const’ qualifier from
> > pointer target type [-Wdiscarded-qualifiers]
> >   info.disassembler_options = disassembler_options;
> >
> > So convert 'const char *' type into 'char *' to fix the warning.
> >
...
> > --- a/tools/bpf/bpftool/jit_disasm.c
> > +++ b/tools/bpf/bpftool/jit_disasm.c
> > @@ -116,7 +116,7 @@ void disasm_print_insn(unsigned char *image, ssize_t
> > len, int opcodes,
> >     info.arch = bfd_get_arch(bfdf);
> >     info.mach = bfd_get_mach(bfdf);
> >     if (disassembler_options)
> > -        info.disassembler_options = disassembler_options;
> > +        info.disassembler_options = (char *)disassembler_options;
> >     info.buffer = image;
> >     info.buffer_length = len;

At some point someone may decide to build with -Wcast-const
at which point you've just generated a different error.

The (probably) correct fix is to make info.disassempler_options 'const char *'.

	David

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