pete added a comment. In https://reviews.llvm.org/D30882#1075461, @dexonsmith wrote:
> In https://reviews.llvm.org/D30882#1075407, @ddunbar wrote: > > > In https://reviews.llvm.org/D30882#1074822, @dexonsmith wrote: > > > > > I don't think this is quite right. I know at least `make`-based > > > incremental builds wouldn't deal well with this. > > > > > > This is actually not a novel problem w.r.t. this patch. The exact same > > situation comes up with Makefile-included .d files and when one of the > > referenced headers is removed. > > > > This is typically solved somewhere in the build system, for example Make > > has `-include`, and Ninja and llbuild have explicit support for this > > situation. > > > Of course, yes, I was wrong. Thanks for the correction. > > > I agree we might want to tread cautiously on how we change the .d output, > > but in this case I think it might be safe. > > > > If we decide this isn't safe, then we may want to consider a new flag which > > tracks *all* anti-dependencies (file's for which Clang checked existence > > but did not exist), and include that here. The major concern with that > > approach is it is a much larger list, and while it would support being > > substantially more correct, it is also well beyond what people currently > > expect out of the build system + compiler generated deps approaches. > > Even though this is likely safe, it seems really noisy. Consider the case > where someone has `__has_include(<missing>)` -- we'll get an entry for every > `-I`, `-F`, `-isystem`, and `-iframework`. If we're going to add that noise, > I prefer a separate flag that covers all anti-dependencies. Oh, that actually wasn't my intention when I wrote it. Honestly I didn't expect it to log anything for missing paths at all, as we don't currently log all the missing (but attempted) paths for regular #include's. Would it be ok to turn this on by default, without a flag, only in the case of the path actually existing, and only the found path being the one we add to the .d? https://reviews.llvm.org/D30882 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
