On Jun 18, 2012, at 15:42 , Richard Smith <[email protected]> wrote:
> On Mon, Jun 18, 2012 at 3:28 PM, Jordan Rose <[email protected]> wrote: >> >> On Jun 18, 2012, at 15:23 , Eli Friedman <[email protected]> wrote: >> >>> On Mon, Jun 18, 2012 at 3:09 PM, Jordan Rose <[email protected]> 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? I skipped the literal type check; currently it allows all const variables with initializers, literal or not. There's also no check for the address clause (which I mistakenly interpreted as equivalent to "prvalue only", but which allows references). Those checks won't cause us to reject valid code. The only valid code we will reject under -pedantic-errors here is code that references internal linkage / anonymous namespace non-constant variables or functions from a file that is included in one translation unit in the entire compilation. From the perspective of perfection, this is technically incorrect, and for -pedantic-errors that may be what we want. But there is never a case where this is not fixable (by putting the offending function/method in an anonymous namespace), and if someday the included file shows up in two translation units you have a legitimate pedantic-error which could affect the behavior of your program. I'm genuinely not sure which is worse: missing an error because we don't do cross-TU checking, or preventing compilation on the case where something is only included once. We'd warn whether it's ExtWarn or Warning, so that's not the issue. _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
