tbaeder marked 9 inline comments as done.
tbaeder added inline comments.
================
Comment at: clang/lib/AST/Interp/ByteCodeExprGen.cpp:835
IsTemporary = true;
Ty = E->getType();
}
----------------
shafik wrote:
> Do we really want to the type of the expression? If we have a `ValueDecl`
> don't we want that type? I think they should be the same, do you have any
> examples where the expression is the type we want? I am looking at the AST
> from ` int x = 1+1L;`
>
> https://godbolt.org/z/q3Tr7Kxoq
I don't have a counter example but I didn't write that line either. The Expr
case is for temporary values created for AST expressions, not sure what other
type to use.
================
Comment at: clang/lib/AST/Interp/InterpBlock.h:97
void invokeCtor() {
- std::memset(data(), 0, getSize());
+ std::memset(rawData(), 0, Desc->getAllocSize());
if (Desc->CtorFn)
----------------
aaron.ballman wrote:
> tbaeder wrote:
> > aaron.ballman wrote:
> > > tbaeder wrote:
> > > > aaron.ballman wrote:
> > > > > Why do we want to overwrite the metadata here?
> > > > This is only called after creating an new block, so nothing is being
> > > > overwritten, the metadata hasn't been filled-in yet.
> > > Sounds like a good reason not to memset over that block then; it's
> > > useless work that will be thrown away anyway (I worry we may come to rely
> > > on this zero init accidentally)?
> > FWIW I looked into this and I think zeroing everything is what we want, so
> > the initmap is null initially
> Hmmm, would it make more sense to have the init map setting that itself (in
> `allocate()`) rather than relying on `invokeCtor()` to do it?
It's a bit blurry to me regarding the layering with Pointer/Descriptor.
Descriptors don't know anything about the metadata, but pointers know that
primitive arrays have an initmap. So to keep that consistent, we'd have to
create a pointer to create the initmap.
But I don't think it's unreasonable to expect zero-initialization for types
used in the interpreter.
================
Comment at: clang/test/AST/Interp/cxx20.cpp:93
+ // ref-note {{read of uninitialized object is not allowed in a
constant expression}}
+}
+static_assert(initializedLocal3() == 20); // expected-error {{not an integral
constant expression}} \
----------------
It might be interesting to know that the output for this test changes with
https://reviews.llvm.org/D135750. After that patch, we only note that the
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D135750/new/
https://reviews.llvm.org/D135750
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