================
@@ -3922,6 +3922,42 @@ bool Sema::MergeFunctionDecl(FunctionDecl *New,
NamedDecl *&OldD, Scope *S,
return true;
}
+ const auto OldFX = Old->getFunctionEffects();
+ const auto NewFX = New->getFunctionEffects();
+ if (OldFX != NewFX) {
+ const auto Diffs = FunctionEffectSet::differences(OldFX, NewFX);
+ for (const auto &Item : Diffs) {
+ const FunctionEffect *Effect = Item.first;
+ const bool Adding = Item.second;
+ if (Effect->diagnoseRedeclaration(Adding, *Old, OldFX, *New, NewFX)) {
+ Diag(New->getLocation(),
+ diag::warn_mismatched_func_effect_redeclaration)
+ << Effect->name();
+ Diag(Old->getLocation(), diag::note_previous_declaration);
+ }
+ }
+
+ const auto MergedFX = OldFX | NewFX;
+
+ // Having diagnosed any problems, prevent further errors by applying the
+ // merged set of effects to both declarations.
+ auto applyMergedFX = [&](FunctionDecl *FD) {
+ const auto *FPT = FD->getType()->getAs<FunctionProtoType>();
+ FunctionProtoType::ExtProtoInfo EPI = FPT->getExtProtoInfo();
+ EPI.FunctionEffects = MergedFX;
+ QualType ModQT = Context.getFunctionType(FD->getReturnType(),
+ FPT->getParamTypes(), EPI);
+
+ FD->setType(ModQT);
+ };
+
+ applyMergedFX(Old);
+ applyMergedFX(New);
+
+ OldQType = Old->getType();
----------------
Sirraide wrote:
@dougsonos So, update, I just talked to Aaron about this, and generally
speaking, it’s better to avoid modifying the `Old` declaration (even in cases
where it wouldn’t change the behaviour of the program) as that may be a source
of possible confusion for e.g. tools that are consuming the AST but don’t know
about this.
I think I’ve mentioned this already, but an alternative that comes to mind
would be to just look at all declarations of a function (starting at the most
recent one, because that one will most likely have the attribute on it) and
consider a function to be effectively `nolock`/`noalloc` if any of them are
`nolock`/`noalloc`. Iirc, there was some code somewhere that is only checking
the canonical decl, so that would have to be updated as a result.
https://github.com/llvm/llvm-project/pull/84983
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