[cfe-commits] r164143 - in /cfe/trunk: include/clang/Basic/DiagnosticGroups.td include/clang/Basic/DiagnosticSemaKinds.td lib/Sema/SemaChecking.cpp test/Analysis/additive-folding.cpp test/Sema/compare.c test/Sema/outof-range-constant-compare.c te

[Douglas Gregor]

On Sep 25, 2012, at 2:40 PM, John McCall <rjmccall at apple.com> wrote:

> On Sep 25, 2012, at 8:29 AM, Hans Wennborg wrote:
>> On Tue, Sep 18, 2012 at 6:37 PM, Fariborz Jahanian <fjahanian at apple.com> wrote:
>>> Author: fjahanian
>>> Date: Tue Sep 18 12:37:21 2012
>>> New Revision: 164143
>>> 
>>> URL: http://llvm.org/viewvc/llvm-project?rev=164143&view=rev
>>> Log:
>>> c: warn when an integer value comparison with an
>>> integral expression have the obvious result.
>>> Patch reviewed by John McCall off line.
>>> // rdar://12202422
>> 
>> This triggers a couple of warnings in Chromium. (We're tracking it at
>> http://crbug.com/151927) Most look like bugs, but this one doesn't
>> really:
>> 
>> /usr/local/google/work/chrome/src/v8/src/utils.h:977:20: warning:
>> comparison of constant 32 with expression of type
>> 'v8::internal::AstPropertiesFlag' is always true
>> [-Wtautological-constant-out-of-range-compare]
>>   ASSERT(element < static_cast<int>(sizeof(T) * CHAR_BIT));
>>   ~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> 
>> The code, with context, is available at [1]. This is in a class
>> template, and 'element' has the type of a template parameter, so
>> depending on what type the template is instantiated with, the
>> comparison might be tautological or not. Perhaps the warning shouldn't
>> fire for expressions that depend on template parameters?
> 
> Yes, I think this is probably a reasonable request for all of the
> tautological-comparison warnings.


FWIW, this is another instance of the longstanding bug

	http://llvm.org/bugs/show_bug.cgi?id=8682


	- Doug