rjmccall added inline comments.
================
Comment at: clang/lib/Sema/SemaExpr.cpp:677
+ E->getType().isDestructedType() == QualType::DK_nontrivial_c_struct)
+ Cleanup.setExprNeedsCleanups(true);
+
----------------
ahatanak wrote:
> rjmccall wrote:
> > ahatanak wrote:
> > > rjmccall wrote:
> > > > Why only when the l-value is volatile?
> > > I was trying to avoid emitting `ExprWithCleanups` when it wasn't needed
> > > and it seemed that it wasn't needed for non-volatile types. I'm not sure
> > > it's important, so I've removed the check for volatile. Also,
> > > `ExprWithCleanups` shouldn't' be emitted when this is in file scope, so I
> > > fixed that too.
> > Hmm, not sure about this file-scope thing, since the combination of C++
> > dynamic initializers and statement-expressions means we can have pretty
> > unrestricted code there.
> I should have explained why this was needed, but I wanted to prevent emitting
> `ExprWithCleanups` in the following example:
>
> ```
> struct A {
> id f0;
> };
>
> typedef struct A A;
>
> A g = (A){ .f0 = 0 };
> ```
>
> The l-value to r-value conversion happens here because compound literals are
> l-values. Since `g` is a global of a non-trivial C struct type, we shouldn't
> try to push a cleanup and destruct the object.
>
> We don't have to think about the C++ case since the line below checks the
> type is a non-trivial C type. I didn't think about statement expressions, but
> they aren't allowed in file scope, so I guess that's not a problem either.
I would hope that the constant-evaluator here might be smart enough to ignore
some elidable temporaries.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D66094/new/
https://reviews.llvm.org/D66094
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