> On Feb 27, 2015, at 4:46 PM, Rick Mann <rm...@latencyzero.com> wrote:
>
>
>> On Feb 27, 2015, at 16:45 , Greg Parker <gpar...@apple.com> wrote:
>>
>>
>>> On Feb 27, 2015, at 4:28 PM, Rick Mann <rm...@latencyzero.com> wrote:
>>>
>>> I'm updating some older Core Data code in which I made liberal use of
>>> transient properties to map NSNumber* types to scalar types like uint32_t.
>>> In practice, this doesn't gain much, especially with boxing syntax, and it
>>> makes the Core Data classes messier (shadow attributes, etc.).
>>>
>>> The problem is, if I change an attribute's type to NSNumber*, and fail to
>>> modify every reference to that attribute, I often end up comparing
>>> pointers, not values:
>>>
>>> @property (strong) NSNumber* someAttribute;
>>>
>>> if (obj.someAttribute > 42)
>>>
>>> which needs to become:
>>>
>>> if (obj.someAttribute.integerValue > 42)
>>>
>>> I'd love an explicit warning for misuse of NSNumber*, but a pointer-integer
>>> comparison warning would be helpful. However, I don't see that among the
>>> available warnings in Xcode.
>>
>> Here's how to answer "is there a warning for X".
>> 1. Write a test file with the line of code that you want to be warned about.
>> 2. Compile that file with -Weverything which enables literally every warning
>> supported by the compiler.
>> 3. If the compiler warns about the code then the diagnostic message will
>> print the name of the warning flag, if any. Example:
>> test.m:13:1: warning: control reaches end of non-void function
>> [-Wreturn-type]
>> If it doesn't print a warning name then that warning is on all the time, I
>> think.
>>
>> When I run a test of your code, I get a warning unconditionally. It's
>> possible that my compiler is newer than yours; in your compiler there might
>> be no warning, or there might be a warning behind some warning flag. Try it
>> yourself.
>>
>> test.m:12:13: warning: ordered comparison between pointer and integer
>> ('NSNumber *' and 'int')
>> if (t.x > 42) printf("bigger");
>> ~~~ ^ ~~
>
> Great suggestion. Some versions of GCC will also tell you the command-line
> option that controls the warning it's emitting. I wish clang did that.
Er, that's exactly what Clang does, when there is a command-line option.
Example:
test.m:13:1: warning: control reaches end of non-void function [-Wreturn-type]
Some of clang's warnings have no command-line option. Ordered comparison
between pointer and integer appears to be one of them, at least in my version
of the compiler.
--
Greg Parker gpar...@apple.com Runtime Wrangler
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