[Lldb-commits] [PATCH] D136011: [lldb] Don't check environment default char signedness when creating clang type for "char"

Mon Oct 17 06:45:45 PDT 2022

labath added a comment.

In D136011#3860637 <https://reviews.llvm.org/D136011#3860637>, @dblaikie wrote:

> I think the place where this will go wrong is in terms of how lldb renders `char` values on non-default-char-signedness programs (it'll render them as the default-char-signedness, which might be confusing to a user - since they'll be looking at literals, etc, that are the other signedness) and how lldb will interpret char literals (though that'll already be wrong - since the literals are already being parsed with the default-char-signedness, I think).

Yes, I'm pretty sure that will happen. OTOH, I don't think there's any value to fix this in a completely satisfactory way. Like, if the whole program was consistently with the non-default signedness, we could try to detect it and then configure the internal AST defaults accordingly. But that's hard to detect, and I'd be surprised if most programs are completely homogeneous like this.

So, overall, I quite like this fix.

> I'm curious why there were all those expected failures re: PR23069. Were they not using the default char signedness? Or is the test using explicit signedness, and so whatever platforms happen not to have the explicit value sa their default are/were failing?

Yes, I'm pretty sure that's the case.

In D136011#3861792 <https://reviews.llvm.org/D136011#3861792>, @DavidSpickett wrote:

>> With -f(un)signed-char, the die corresponding to "char" may be the wrong DW_ATE_(un)signed_char.
>
> As the producer of the DWARF (so, clang for example) is this correct by the existing rules?

Yes, because DWARF never expected people will be round-tripping the debug info back into C(++). As far as it is concerned, it has correctly given you the signedness of the type.

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