[cfe-commits] r158683 - in /cfe/trunk: include/clang/Basic/DiagnosticSemaKinds.td lib/Sema/SemaExpr.cpp test/Sema/inline.c test/SemaCXX/inline.cpp

[Richard Smith]

On Mon, Jun 18, 2012 at 3:28 PM, Jordan Rose <jordan_rose at apple.com> wrote:
>
> On Jun 18, 2012, at 15:23 , Eli Friedman <eli.friedman at gmail.com> wrote:
>
>> On Mon, Jun 18, 2012 at 3:09 PM, Jordan Rose <jordan_rose at apple.com> wrote:
>>> Author: jrose
>>> Date: Mon Jun 18 17:09:19 2012
>>> New Revision: 158683
>>>
>>> URL: http://llvm.org/viewvc/llvm-project?rev=158683&view=rev
>>> Log:
>>> Support -Winternal-linkage-in-inline in C++ code.
>>>
>>> This includes treating anonymous namespaces like internal linkage, and allowing
>>> const variables to be used even if internal. The whole thing's been broken out
>>> into a separate function to avoid nested ifs.
>>
>> I think it's worth pointing out that in the C++ case, the given
>> testcase doesn't strictly violate ODR because the  definition of the
>> function in question isn't actually used in multiple files.  Because
>> of that, it shouldn't be an error with -pedantic-errors (the
>> diagnostic should use Warning rather than Extension/ExtWarn), and you
>> should watch to see if there are any bug reports with false positives.
>> (I think false positives are unlikely, but not impossible.)
>
> Ah, I see. Without cross-TU analysis, we can't tell if a function is used in multiple files or not. I think it's valid to leave this as ExtWarn when it's in a header file…it's kind of a ticking time bomb.

-pedantic-errors shouldn't cause us to reject valid code, and not all
#included files are intended to be included multiple times (we have
several examples of this in Clang, with (for instance) files generated
by tablegen).

Have you considered implementing the check for whether a variable used
within such an inline function has a literal type (or, in C++98, an
integral or enumeration type), and checking whether the initializer is
a constant expression?

Checking whether the variable's address is used seems trickier,
perhaps we can use the result of the odr-use checking mechanism?