[PATCH] D73457: [Clang] Warn about 'z' printf modifier in old MSVC.

Mon Jan 27 10:57:25 PST 2020

aaron.ballman accepted this revision.
aaron.ballman added a comment.
This revision is now accepted and ready to land.

LGTM!

In D73457#1842605 <https://reviews.llvm.org/D73457#1842605>, @amccarth wrote:

> In D73457#1842493 <https://reviews.llvm.org/D73457#1842493>, @simon_tatham wrote:
>
> > Removed the special case for `MSCompatibilityVersion == 0`. If the default compatibility setting needs to be changed, that's a separate piece of work and should be done by someone who understands more than I do about all those failing tests :-) The new version of this patch just uses the existing default.
>
>
> +1.  The issue of how the default version gets set is a separate issue.  I think it's best to keep this patch decoupled from that.

Definitely agreed! I just didn't want to do duplicate work if there was a bug elsewhere that would impact how we proceed here.

>> With the typical command line I use with the `clang-cl` driver, a specific version has been set anyway by the time cc1 is running. So probably I shouldn't have been worrying in the first place about what happens if there isn't one set.
> 
> The default you found for MSVC15 is the last result default.  (Though I would have expected that to be MSVC17 by now.)  I believe the driver will actually try to figure out the most recent version of MSVC installed on the machine (assuming it's Windows), and use that.  Only if it can't find one, will it use that default.
> 
> As I recall, this is because clang will still (by default) use the MS runtime libraries for Windows builds, in which case it's important for the compatibility version to match the one for the libraries that are going to be used.  I think we can/should reconsider this when clang-cl starts using different run-time libraries for Windows builds.

Ah, thank you for that context!

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https://reviews.llvm.org/D73457