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Re: [PATCH] Introduce in_inclusive_range, fix -Wtautological-compare warnings
On 10/30/17 2:32 PM, Simon Marchi wrote:
> When compiling with clang or gcc 8, we see warnings like this:
>
> /home/emaisin/src/binutils-gdb/gdb/arm-tdep.c:10013:13: error: comparison of 0 <= unsigned expression is always true [-Werror,-Wtautological-compare]
> if (0 <= insn_op1 && 3 >= insn_op1)
> ~ ^ ~~~~~~~~
> /home/emaisin/src/binutils-gdb/gdb/arm-tdep.c:11722:20: error: comparison of unsigned expression >= 0 is always true [-Werror,-Wtautological-compare]
> else if (opB >= 0 && opB <= 2)
> ~~~ ^ ~
>
> This is because an unsigned integer (opB in this case) will always be >=
> 0. It is still useful to keep both bounds of the range in the
> expression, even if one is at the edge of the data type range. This
> patch introduces a utility function in_inclusive_range that gets rid of
> the warning while conveying that we are checking for a range.
>
> Tested by rebuilding.
>
> gdb/ChangeLog:
>
> * common/common-utils.h (in_inclusive_range): New function.
> * arm-tdep.c (arm_record_extension_space): Use
> in_inclusive_range.
> * cris-tdep.c (cris_spec_reg_applicable): Use
> in_inclusive_range.
> ---
> gdb/arm-tdep.c | 4 ++--
> gdb/common/common-utils.h | 9 +++++++++
> gdb/cris-tdep.c | 4 ++--
> 3 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/gdb/cris-tdep.c b/gdb/cris-tdep.c
> index d623eb6..209e29f 100644
> --- a/gdb/cris-tdep.c
> +++ b/gdb/cris-tdep.c
> @@ -1434,7 +1434,7 @@ cris_spec_reg_applicable (struct gdbarch *gdbarch,
> /* Indeterminate/obsolete. */
> return 0;
> case cris_ver_v0_3:
> - return (version >= 0 && version <= 3);
> + return in_inclusive_range (version, 0U, 3U);
> case cris_ver_v3p:
> return (version >= 3);
> case cris_ver_v8:
> @@ -1442,7 +1442,7 @@ cris_spec_reg_applicable (struct gdbarch *gdbarch,
> case cris_ver_v8p:
> return (version >= 8);
> case cris_ver_v0_10:
> - return (version >= 0 && version <= 10);
> + return in_inclusive_range (version, 0U, 10U);
> case cris_ver_v3_10:
> return (version >= 3 && version <= 10);
> case cris_ver_v8_10:
I wonder if in this file it wouldn't be best to use the new function throughout
the various cases so that the style is more consistent? LGTM regardless.
--
John Baldwin