This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
Re: [PATCH] Introduce in_inclusive_range, fix -Wtautological-compare warnings
On 10/30/17 4:01 PM, Simon Marchi wrote:
> On 2017-10-30 11:57, John Baldwin wrote:
>> 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.
>
>
> Good point, I'll make that change. I'll see if it's possible in
> arm-tdep.c too or if it's a too daunting task.
It may be sufficient to just be consistent within a function? In arm-tdep.c
it is two instances in separate functions whereas for cris-tdep.c it is
multiple instances in the same function which is what stuck out to me.
--
John Baldwin