Fix incorrect use of current directory to find moved paths in ASTReader.

[klimek]

Summary

CurrentDir was set as the path of the current module, but that can change as
part of a chain of loaded modules.

When we try to locate a file mentioned in a module that does not exist, we use
a heuristic to look at the relative path between the original location of the
module and the file we look for, and use that relatively to the CurrentDir.

This only works if CurrentDir is the same as the (current) path of the module
file the file was mentioned in; if it is not, we look at the path relatively to
the wrong directory, and can end up reading random unrelated files that happen
to have the same name.

This patch fixes this by using the BaseDirectory of the module file the file
we look for was mentioned in instead of the CurrentDir heuristic.

[bkramer]

lg

include/clang/Serialization/ASTReader.h

public:
   };
 
 private:
   /// \brief A list of modules that were imported by precompiled headers or
   /// any other non-module AST file.
   SmallVector<ImportedSubmodule, 2> ImportedModules;
   //@}
 
-  /// \brief The directory that the PCH we are reading is stored in.
-  std::string CurrentDir;
-
   /// \brief The system include root to be used when loading the
   /// precompiled header.
   std::string isysroot;
 
   /// \brief Whether to disable the normal validation performed on precompiled
   /// headers when they are loaded.
   bool DisableValidation;
 

lib/Serialization/ASTReader.cpp

InputFile ASTReader::getInputFile(ModuleFile &F, unsigned ID, bool Complain) {
   InputFileInfo FI = readInputFileInfo(F, ID);
   off_t StoredSize = FI.StoredSize;
   time_t StoredTime = FI.StoredTime;
   bool Overridden = FI.Overridden;
   bool Transient = FI.Transient;
   StringRef Filename = FI.Filename;
 
   const FileEntry *File = FileMgr.getFile(Filename, /*OpenFile=*/false);
-
   // If we didn't find the file, resolve it relative to the
   // original directory from which this AST file was created.
-  if (File == nullptr && !F.OriginalDir.empty() && !CurrentDir.empty() &&
-      F.OriginalDir != CurrentDir) {
-    std::string Resolved = resolveFileRelativeToOriginalDir(Filename,
-                                                            F.OriginalDir,
-                                                            CurrentDir);
+  if (File == nullptr && !F.OriginalDir.empty() && !F.BaseDirectory.empty() &&
+      F.OriginalDir != F.BaseDirectory) {
+    std::string Resolved = resolveFileRelativeToOriginalDir(
+        Filename, F.OriginalDir, F.BaseDirectory);
     if (!Resolved.empty())
       File = FileMgr.getFile(Resolved);
   }
 
   // For an overridden file, create a virtual file with the stored
   // size/timestamp.
   if ((Overridden || Transient) && File == nullptr)
     File = FileMgr.getVirtualFile(Filename, StoredSize, StoredTime);
case ModuleManager::OutOfDate:
     Diag(diag::err_module_file_out_of_date) << moduleKindForDiagnostic(Type)
                                             << FileName << !ErrorStr.empty()
                                             << ErrorStr;
     return Failure;
   }
 
   assert(M && "Missing module file");
 
-  // FIXME: This seems rather a hack. Should CurrentDir be part of the
-  // module?
-  if (FileName != "-") {
-    CurrentDir = llvm::sys::path::parent_path(FileName);
-    if (CurrentDir.empty()) CurrentDir = ".";
-  }
-
   ModuleFile &F = *M;
   BitstreamCursor &Stream = F.Stream;
   Stream = BitstreamCursor(PCHContainerRdr.ExtractPCH(*F.Buffer));
   F.SizeInBits = F.Buffer->getBufferSize() * 8;
 
   // Sniff for the signature.
   if (!startsWithASTFileMagic(Stream)) {
     Diag(diag::err_module_file_invalid) << moduleKindForDiagnostic(Type)

test/Modules/path-resolution.modulemap

+// RUN: rm -rf %t
+//
+// First, create two modules a and b, with a dependency b -> a, both within
+// the same directory p1.
+//
+// RUN: mkdir -p %t/p1
+// RUN: cd %t/p1
+//
+// RUN: grep "<AM>" %s > %t/p1/a.modulemap
+// RUN: %clang_cc1 -x c++ -fmodules -emit-module -fmodule-map-file-home-is-cwd \
+// RUN:   -fmodules-embed-all-files -fmodules-local-submodule-visibility \
+// RUN:   -fmodule-name="a" -o a.pcm a.modulemap
+//
+// RUN: grep "<BM>" %s > %t/p1/b.modulemap
+// RUN: %clang_cc1 -x c++ -fmodules -emit-module -fmodule-map-file-home-is-cwd \
+// RUN:   -fmodules-embed-all-files -fmodules-local-submodule-visibility \
+// RUN:   -fmodule-name="b" -o b.pcm b.modulemap
+//
+// Next, move the whole tree p1 -> p2.
+//
+// RUN: cd %t
+// RUN: mv %t/p1 %t/p2
+// RUN: cd %t/p2
+//
+// Compile a new module c in the newly generated tree that depends on b; c.pcm
+// has to be within a subdirectory so a.modulemap will be one step up (../) from
+// c.pcm.
+//
+// RUN: mkdir %t/p2/c
+// RUN: grep "<CM>" %s > %t/p2/c/c.modulemap
+// RUN: grep "<CH>" %s > %t/p2/c/c.h
+// RUN: %clang_cc1 -x c++ -fmodules -emit-module -fmodule-map-file-home-is-cwd \
+// RUN:   -fmodules-embed-all-files -fmodules-local-submodule-visibility \
+// RUN:   -fmodule-name="c" -fmodule-file=b.pcm -o c/c.pcm c/c.modulemap
+//
+// Delete a.modulemap from its original location, and instead inject a different
+// (unrelated) a.modulemap in the path p2/p2.
+//
+// RUN: rm %t/p2/a.modulemap
+// RUN: mkdir -p %t/p2/p2
+// RUN: touch %t/p2/p2/a.modulemap
+//
+// Now compile a file c.cpp that uses c.h and the module c; it is important
+// to first load b.pcm and a.pcm before c.pcm on the command line to trigger
+// the right order of module loading. This used to trigger clang to find the
+// p2/p2/a.modulemap via the path c/../p2/a.modulemap, which is not the correct
+// relative path from c.
+//
+// RUN: grep "<CC>" %s > %t/p2/c/c.cpp
+// RUN: %clang_cc1 -I. -x c++ -fmodules \
+// RUN:     -fmodule-file=b.pcm -fmodule-file=a.pcm -fmodule-file=c/c.pcm  \
+// RUN:     -o c/c.o -emit-obj c/c.cpp
+
+module "a" {                // <AM>
+}                           // <AM>
+
+module "b" {                // <BM>
+  use "a"                   // <BM>
+}                           // <BM>
+
+module "c" {                // <CM>
+  header "c/c.h"            // <CM>
+  use "a"                   // <CM>
+  use "b"                   // <CM>
+}                           // <CM>
+
+inline void c() {}          // <CH>
+
+#include "c/c.h"            // <CC>
+void foo() { c(); }         // <CC>