Add flag for showing skipped headers in -H / --show-includes output

Consider the following set of files:

  a.cc:
  #include "a.h"

  a.h:
  #ifndef A_H
  #define A_H

  #include "b.h"
  #include "c.h"  // This gets "skipped".

  #endif

  b.h:
  #ifndef B_H
  #define B_H

  #include "c.h"

  #endif

  c.h:
  #ifndef C_H
  #define C_H

  void c();

  #endif

And the output of the -H option:

  $ clang -c -H a.cc
  . ./a.h
  .. ./b.h
  ... ./c.h

Note that the include of c.h in a.h is not shown in the output (GCC does the
same). This is because of the include guard optimization: clang knows c.h is
covered by an include guard which is already defined, so when it sees the
include in a.h, it skips it. The same would have happened if #pragma once were
used instead of include guards.

However, a.h *does* include c.h, and it may be useful to show that in the -H
output. This patch adds a flag for doing that.

Differential revision: https://reviews.llvm.org/D100480

1 files changed, 16 insertions, 0 deletions

diff --git a/clang/lib/Frontend/HeaderIncludeGen.cpp b/clang/lib/Frontend/HeaderIncludeGen.cpp
index df3f534..1ee47d8 100644
--- a/clang/lib/Frontend/HeaderIncludeGen.cpp
+++ b/clang/lib/Frontend/HeaderIncludeGen.cpp
@@ -45,6 +45,9 @@ public:
   void FileChanged(SourceLocation Loc, FileChangeReason Reason,
                    SrcMgr::CharacteristicKind FileType,
                    FileID PrevFID) override;
+
+  void FileSkipped(const FileEntryRef &SkippedFile, const Token &FilenameTok,
+                   SrcMgr::CharacteristicKind FileType) override;
 };
 }
 
@@ -181,3 +184,16 @@ void HeaderIncludesCallback::FileChanged(SourceLocation Loc,
                     MSStyle);
   }
 }
+
+void HeaderIncludesCallback::FileSkipped(const FileEntryRef &SkippedFile, const
+                                         Token &FilenameTok,
+                                         SrcMgr::CharacteristicKind FileType) {
+  if (!DepOpts.ShowSkippedHeaderIncludes)
+    return;
+
+  if (!DepOpts.IncludeSystemHeaders && isSystem(FileType))
+    return;
+
+  PrintHeaderInfo(OutputFile, SkippedFile.getName(), ShowDepth,
+                  CurrentIncludeDepth + 1, MSStyle);
+}