rjmccall added inline comments.
================
Comment at: lib/CodeGen/CodeGenModule.h:354
@@ +353,3 @@
+ /// call).
+ llvm::DenseSet<GlobalDecl> ExplicitDefinitions;
+
----------------
andreybokhanko wrote:
> Checking that a GlobalDecl is not in ExplicitDefinitions yet is actually
> required to avoid printing multiple identical warnings.
>
> In my example:
>
> ```
> 1: struct T {
> 2: ~T() {}
> 3: };
> 4:
> 5: extern "C" void _ZN1TD1Ev();
> 6:
> 7: int main() {
> 8: _ZN1TD1Ev();
> 9: T t;
> 10: }
> ```
>
> ~T() is added to the list of deferred decls twice. Judging from this comment
> in "EmitDeferred" method:
>
> // Check to see if we've already emitted this. This is necessary
> // for a couple of reasons: first, decls can end up in the
> // deferred-decls queue multiple times, and second, decls can end
> // up with definitions in unusual ways (e.g. by an extern inline
> // function acquiring a strong function redefinition). Just
> // ignore these cases.
>
> this is pretty normal ("decls can end up in the deferred-decls queue multiple
> times").
>
> This means that we can call "GetOrCreateLLVMFunction"(...,
> /*IsForDefinition*/=true) for duplicated decls several times, which is fine
> in general, *but* will print the "duplicated mangled names" diagnostic
> multiple times as well -- unless we check that we already printed a warning
> on duplicated mangled names for given decl.
>
> As for not emitting diagnostics for different globals -- this won't happen,
> as we will call "GetOrCreateLLVMFunction" at least once for each global with
> a definition, and thus, will print a warning for everyone.
>
> I thought really hard (honestly!) on how to prevent duplicated diagnostics
> without usage of an additional set, but didn't found any solution. If you
> have any hints here, they would be much appreciated.
Okay, that's fine. Can you at least make sure you only add to the set when you
emit the warning?
As a minor optimization, you can add it to the set and check whether it was
already there in the same operation, so that this would look like:
if (LookupRepresentativeDecl(...) &&
DiagnosedConflictingDefinitions.insert(GD).second) {
...
}
http://reviews.llvm.org/D11297
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