> I like this a lot! How does it fare against more complicated macros, though?
As is it doesn't display very helpful diagnostics for complicated macros like
these, and even crashes on some.
A good reason not to try to do textual parsing.
>
> #define CASE1 case 1
> #define CASE(x) case x
> #define MULTI_CASE(x,y) case x: case y:
>
> switch (x) {
> CASE1: break;
> CASE(1U): break;
> MULTI_CASE(2,2): break;
> case 2: break;
> }
>
> As for multi-line case statements, I'd be inclined to simply fall back to the
> dumb version of the warning, rather than trying to format it nicely in the
> output. We already have a note showing where the relevant code is. And I
> wouldn't be worried about casts -- if they're there, the user probably
> thought they were making a difference. (I'd actually be more worried about
> things like parens, but I'd err on the side of including them anyway.)
>
> Jordy
>
>
> On May 15, 2012, at 12:05, Terry Long wrote:
>
>> Hi all,
>>
>> This patch mostly inspired by http://llvm.org/bugs/show_bug.cgi?id=9243 --
>> poor "duplicate case" diagnostic with enums
>>
>> Previously the diagnostic for duplicate case values in switch statements was
>> always something like "duplicate case value '5'"
>>
>> What my patch changes:
>> When the duplicate case is exactly the same in textual representation (in
>> source code), the diagnostic will use that exact text in the diagnostic.
>> e.g. using MyEnum twice gives the diagnostic "duplicate case value 'MyEnum'"
>>
>> If the textual representations differ, the new diagnostic explicitly states
>> they are equal to the same value
>> e.g. using MyEnum (equal to 5) and 5, the diagnostic displays "duplicate
>> case value: 'MyEnum' and '5' both equal '5'"
>>
>> The patch does the same for any valid expression in a case statement
>> (including macros, const ints, char literals, etc.).
>>
>> Concerns with my patch:
>> 1. Multiline case statements, although unusual, will be printed out in the
>> diagnostic exactly as they appear in the source. I'm not sure if this is a
>> real issue. Possible solution would be checking if it spans multiple lines.
>> If so, the diagnostic could be "duplicate case value: both expressions equal
>> 'x'".
>> e.g.
>> case 1 +
>> 2 +
>> 3:
>>
>> 2. If a case statement includes a cast, the cast will also be included in
>> the diagnostic. Sometimes this inclusion is helpful, for example in
>> situations where the cast will cause an overflow (such as "(char)256" and
>> "0"). Other times it is irrelevant, such as "(int)7" and "7", where a simple
>> diagnostic of "duplicate case value '7'" makes more sense. I'm also not sure
>> if this is an issue.
>>
>>
>> Thanks!
>>
>> Terry Long
>>
>> <PR9243.patch>_______________________________________________
>> cfe-commits mailing list
>> [email protected]
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>
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