ahatanak marked an inline comment as done.
ahatanak added inline comments.
================
Comment at: lib/CodeGen/CGExpr.cpp:4100
+ if (E->getType().isDestructedType() == QualType::DK_nontrivial_c_struct)
+ pushDestroy(QualType::DK_nontrivial_c_struct, DeclPtr, E->getType());
+
----------------
rjmccall wrote:
> ahatanak wrote:
> > rjmccall wrote:
> > > ahatanak wrote:
> > > > rjmccall wrote:
> > > > > rjmccall wrote:
> > > > > > Unfortunately, the lifetime of compound literals in C is not this
> > > > > > simple; they're like blocks in that they're destroyed at the end of
> > > > > > the enclosing scope rather than at the end of the current
> > > > > > statement. (The cleanup here will be popped at the end of the
> > > > > > full-expression if we've entered an `ExprWithCleanups`.) And the
> > > > > > l-value case is exactly the case where this matters.
> > > > > >
> > > > > > I think you need to do something like what we do with blocks, where
> > > > > > we record all the blocks in the full-expression on the
> > > > > > `ExprWithCleanups` so that we can push an inactive cleanup for them
> > > > > > and then activate it when we emit the block.
> > > > > Can we make the check here something like (1) this is a block-scope
> > > > > compound literal and (2) it has a non-trivially-destructed type (of
> > > > > any kind)? That way we're not conflating two potentially unrelated
> > > > > elements, the lifetime of the object and the kinds of types that can
> > > > > be constructed by the literal.
> > > > >
> > > > > Oh, actually, there's a concrete reason to do this: C99 compound
> > > > > literals are not required to have struct type; they can have any
> > > > > object type, including arrays but also scalars. So we could, even
> > > > > without non-trivial C structs, have a block-scope compound of type
> > > > > `__strong id[]`; I guess we've always just gotten this wrong. Please
> > > > > add tests for this case. :)
> > > > There is a check `E->isFileScope()` above this. Is that sufficient to
> > > > check for block-scoped compound literals?
> > > That plus the C/C++ difference; compound literals in C++ are just
> > > temporaries.
> > I haven't been able to come up with a piece of C++ code that executes
> > `EmitCompoundLiteralLValue`. The following code gets rejected because you
> > can't take the address of a temporary object in C++:
> >
> > ```
> > StrongSmall *p = &(StrongSmall){ 1, 0 };
> > ```
> >
> > If a bind a reference to it, `AggExprEmitter::VisitCompoundLiteralExpr` is
> > called.
> That makes sense; they're not gl-values in C++. It would be reasonable to
> assert that. But the C++ point does apply elsewhere.
It turns out this function is called in C++ when the compound literal is a
vector type, so I've just added a check for C++ instead of an assert.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D64464/new/
https://reviews.llvm.org/D64464
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