[PATCH] D30882: Add a callback for __has_include and use it for dependency scanning

[Richard Smith - zygoloid via Phabricator via cfe-commits]

rsmith added inline comments.


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Comment at: include/clang/Lex/PPCallbacks.h:263
+  /// \brief Callback invoked when a has_include directive is read.
+  virtual void HasInclude(SourceLocation Loc, const FileEntry *File) {
+  }
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This callback seems pretty unhelpful in the case where lookup of the file failed (you just get a source location). Could we pass in the `FileName` and `IsAngled` flag too (like we do for `InclusionDirective`)? I think that's what (eg) a callback tracking anti-dependencies (for a more sophisticated build system that can handle them) would want.


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Comment at: lib/Frontend/DependencyFile.cpp:325
+void DFGImpl::HasInclude(SourceLocation Loc, const FileEntry *File) {
+  if (!File)
+    return;
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Have you thought about whether we should add a dependency even for a missing file under `-MG` (`AddMissingHeaderDeps`) mode? I think it's probably better to not do so (ie, the behavior in this patch), but it seems worth considering.


https://reviews.llvm.org/D30882