linux-kernel - Re: [bug report] perf jit: add source line info support

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Message-ID: <CABPqkBTU6N3mq79OzRRoUvo=Z3bWSqycB=1=_9839c1wXQGctw@mail.gmail.com>
Date:   Fri, 9 Dec 2016 21:16:41 -0800
From:   Stephane Eranian <eranian@...gle.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [bug report] perf jit: add source line info support

Hi Dan,

On Wed, Nov 30, 2016 at 10:48 AM, Dan Carpenter
<dan.carpenter@...cle.com> wrote:
> Hello Stephane Eranian,
>
> The patch 598b7c6919c7: "perf jit: add source line info support" from
> Nov 30, 2015, leads to the following static checker warning:
>
>         ./tools/perf/util/genelf_debug.c:211 emit_signed_LEB128()
>         warn: potential left shift more than type allows '57'
>
> ./tools/perf/util/genelf_debug.c
>    202  static void emit_signed_LEB128(struct buffer_ext *be, long data)
>    203  {
>    204          int more = 1;
>    205          int negative = data < 0;
>    206          int size = sizeof(long) * CHAR_BIT;
>    207          while (more) {
>    208                  ubyte cur = data & 0x7F;
>    209                  data >>= 7;
>    210                  if (negative)
>    211                          data |= - (1 << (size - 7));
>                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
> This is a no-op on 64 bit systems.  I suspect it's not intentional?
>
I suspect size should be: size = sizeof(int) * CHAR_BIT;
I will test that.

>    212                  if ((data == 0 && !(cur & 0x40)) ||
>    213                      (data == -1l && (cur & 0x40)))
>    214                          more = 0;
>    215                  else
>    216                          cur |= 0x80;
>    217                  buffer_ext_add(be, &cur, 1);
>    218          }
>    219  }
>
> regards,
> dan carpenter