| Message ID | 20190328141652.wssqboyekxmp6tkw@yubo-2 |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | bpf: bpftool: convert ‘const char *’ type into 'char *' in assignment | expand |
2019-03-28 10:16 UTC-0400 ~ Bo YU <tsu.yubo@gmail.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. > > Fixes:3ddeac6705aba(tools: bpftool: use 4 context mode for the NFP disasm) > Signed-off-by: Bo YU <tsu.yubo@gmail.com> > --- > tools/bpf/bpftool/jit_disasm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/bpf/bpftool/jit_disasm.c > b/tools/bpf/bpftool/jit_disasm.c > index 3ef3093560ba..40b46e46454a 100644 > --- 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; > Hi, the warning does not show with latest versions of binutils, it was fixed with this (binutils) commit: commit f995bbe8e62fdb5607acb1ee127240cfe50d2b8f Author: Pedro Alves <palves@redhat.com> Date: Wed Apr 5 19:21:33 2017 +0100 -Wwrite-strings: Constify struct disassemble_info's disassembler_options field Distributions with recent binutils (Ubuntu 18.04, Fedora 29 at least) should not have this message. I thought about sending the same patch some time ago, but in the end Jakub and I decided that it may not be worth casting the const away to silence the warning just for older distributions. Daniel also shared the same opinion at the time (but that was off the mailing-list). Quentin
On 3/28/2019 7:46 PM, Bo YU wrote: > 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. > > Fixes:3ddeac6705aba(tools: bpftool: use 4 context mode for the NFP > disasm) > Signed-off-by: Bo YU <tsu.yubo@gmail.com> Reviewed-by: Mukesh Ojha <mojha@codeaurora.org> -Mukesh > --- > tools/bpf/bpftool/jit_disasm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/tools/bpf/bpftool/jit_disasm.c > b/tools/bpf/bpftool/jit_disasm.c > index 3ef3093560ba..40b46e46454a 100644 > --- 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; >
On Thu, Mar 28, 2019 at 10:33 PM Quentin Monnet <quentin.monnet@netronome.com> wrote: > > 2019-03-28 10:16 UTC-0400 ~ Bo YU <tsu.yubo@gmail.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. > > > > Fixes:3ddeac6705aba(tools: bpftool: use 4 context mode for the NFP disasm) > > Signed-off-by: Bo YU <tsu.yubo@gmail.com> > > --- > > tools/bpf/bpftool/jit_disasm.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/tools/bpf/bpftool/jit_disasm.c > > b/tools/bpf/bpftool/jit_disasm.c > > index 3ef3093560ba..40b46e46454a 100644 > > --- 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; > > > > > Hi, the warning does not show with latest versions of binutils, it was > fixed with this (binutils) commit: > > commit f995bbe8e62fdb5607acb1ee127240cfe50d2b8f > Author: Pedro Alves <palves@redhat.com> > Date: Wed Apr 5 19:21:33 2017 +0100 > > -Wwrite-strings: Constify struct disassemble_info's > disassembler_options field > > Distributions with recent binutils (Ubuntu 18.04, Fedora 29 at least) > should not have this message. I thought about sending the same patch > some time ago, but in the end Jakub and I decided that it may not be > worth casting the const away to silence the warning just for older > distributions. Daniel also shared the same opinion at the time (but that > was off the mailing-list). Ok, good to know it. Thanks, > > Quentin
From: Quentin Monnet > Sent: 28 March 2019 14:31 > 2019-03-28 10:16 UTC-0400 ~ Bo YU <tsu.yubo@gmail.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 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
2019-03-28 15:08 UTC+0000 ~ David Laight <David.Laight@ACULAB.COM> > From: Quentin Monnet >> Sent: 28 March 2019 14:31 >> 2019-03-28 10:16 UTC-0400 ~ Bo YU <tsu.yubo@gmail.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 > Which is what this binutils commit I cited does :) Quentin
diff --git a/tools/bpf/bpftool/jit_disasm.c b/tools/bpf/bpftool/jit_disasm.c index 3ef3093560ba..40b46e46454a 100644 --- 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;
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. Fixes:3ddeac6705aba(tools: bpftool: use 4 context mode for the NFP disasm) Signed-off-by: Bo YU <tsu.yubo@gmail.com> --- tools/bpf/bpftool/jit_disasm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)