[clang] Propagate lifetimebound from formal parameters to those in the canonical declaration and use that for analysis (PR #107627)
Ilya Biryukov via cfe-commits
cfe-commits at lists.llvm.org
Mon Nov 18 10:17:22 PST 2024
================
@@ -266,6 +262,20 @@ void Sema::inferLifetimeBoundAttribute(FunctionDecl *FD) {
LifetimeBoundAttr::CreateImplicit(Context, FD->getLocation()));
}
}
+ } else if (auto *CanonDecl = FD->getCanonicalDecl(); FD != CanonDecl) {
+ // Propagate the lifetimebound attribute from parameters to the canonical
+ // declaration.
+ // Note that this doesn't include the implicit 'this' parameter, as the
+ // attribute is applied to the function type in that case.
+ const unsigned int NP = std::min(NumParams, CanonDecl->getNumParams());
+ for (unsigned int I = 0; I < NP; ++I) {
+ auto *CanonParam = CanonDecl->getParamDecl(I);
+ if (!CanonParam->hasAttr<LifetimeBoundAttr>() &&
+ FD->getParamDecl(I)->hasAttr<LifetimeBoundAttr>()) {
----------------
ilya-biryukov wrote:
Should we be looking at the attributes of the most recent decl instead, then?
How do other mergable attributes handle that?
I think it's fairly important to have a single place in the AST that handles the merging logic for the attributes, even if that means changing some mechanism of how other places work.
Looking at that test, I guess what happens is:
- the attributes get propagated to the **new** redeclaration, but never to the original declaration;
- the canonical declaration is the old one that does not have the attribute;
- when checking for the lifetimebound attribute, we look at canonical declaration and don't notice the attribute.
I will look into the code, but could you check if it makes sense to put something like `getMostRecentDecl()` calls when checking for presence of the attributes?
PS the meta-suggestion here is to not add new ways to merge attributes. I am not sure if it there is a new way that would make more sense, e.g. maybe we can explore merging all the attributes into a canonical declaration instead or ensuring there is a helper function that calls `getMostRecentDecl` before checking for an attribute being present.
https://github.com/llvm/llvm-project/pull/107627
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