[PATCH] D135583: [LLVM] Use DWARFv4 bitfields when tuning for GDB

[David Blaikie via Phabricator via llvm-commits]

dblaikie added a comment.

In D135583#3855256 <https://reviews.llvm.org/D135583#3855256>, @DavidSpickett wrote:

> GDB 8 was the first version to support DW_AT_data_bit_offset.
>
> Given that we expect GCC 7, which would probably come with a GDB 7, likely best action is to just update the comment and I'll come back to this if/when the minimum moves up.
> (https://llvm.org/docs/GettingStarted.html#host-c-toolchain-both-compiler-and-standard-library)

What minimum compiler we require for building clang is a pretty different question than the one we're dealing with here.

The question I'm roughly trying to answer is - has GCC shipped this feature? If so, we probably can too - because any system shipping older GCC versions is unlikely to be shipping a newer (as yet unreleased, in this case, but when it does release) clang.

>> Got a sense of what GCC does in what versions? Might be a good argument for when/if/how we should use this newer feature... if they're already using it at least.
>
> I will check this out. (it might be that the support in GDB 8 has some holes that GCC accounted for for a while after that)

Possible - if there's evidence of such holes, that's useful, but I don't think we'd have to look too hard - the feature seems fairly isolated and probably whatever version GCC started emitting it is a good enough marker for "it's out there and GDB versions expect it/handle it".


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