Re: [PATCH] gdb/microblaze-tdep.c: Check whether less than zero in conditional expression

[Michael Eager <eager@eagerm.com>]

On 07/20/14 07:03, Chen Gang wrote:
> Use typecast 'size_t' on 'reg', not only avoid the related warning, but
> also check whether less than zero -- for 'reg' is type 'int', and sizeof
> (dwarf2_to_reg_map) is less than 0x7fff.
>
> It is quoted in gdb_assert(), so need check 'reg' whether less than zero.
> And the related warning (with '-W'):
>
>    ../../binutils-gdb/gdb/microblaze-tdep.c:667:3: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
>
> ChangeLog:
>
>   * microblaze-tdep.c (microblaze_dwarf2_reg_to_regnum): Check whether
>   less tha zero in conditional expression.
>
>
> Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
> ---
>   gdb/microblaze-tdep.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gdb/microblaze-tdep.c b/gdb/microblaze-tdep.c
> index 7e89241..9bec260 100644
> --- a/gdb/microblaze-tdep.c
> +++ b/gdb/microblaze-tdep.c
> @@ -664,7 +664,7 @@ static int dwarf2_to_reg_map[78] =
>   static int
>   microblaze_dwarf2_reg_to_regnum (struct gdbarch *gdbarch, int reg)
>   {
> -  gdb_assert (reg < sizeof (dwarf2_to_reg_map));
> +  gdb_assert ((size_t) reg < sizeof (dwarf2_to_reg_map));
>     return dwarf2_to_reg_map[reg];
>   }

I don't see anything in the patch which does what you describe,
checking whether reg is less than zero.  Converting a signed
integer to an unsigned integer is not a way to check whether
it is less than zero.  This is better:

+ gdb_assert (reg >= 0 && (size_t) reg < sizeof (dwarf2_to_reg_map));

I do not see this error message in my build which uses -Wall.
What is your build environment?  Which version of GCC?

-- 
Michael Eager	 eager@eagercon.com
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