Introduce a new BufferResult class to act as the return type of

SourceManager's getBuffer() (and similar) operations. This abstract
can be used to force callers to cope with errors in getBuffer(), such
as missing files and changed files. Fix a bunch of callers to use the
new interface.

Add some very basic checks for file consistency (file size,
modification time) into ContentCache::getBuffer(), although these
checks don't help much until we've updated the main callers (e.g.,
SourceManager::getSpelling()).



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@98585 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 67 insertions, 9 deletions

diff --git a/include/clang/Basic/SourceManager.h b/include/clang/Basic/SourceManager.h
index 015d82a63c..05480419ab 100644
--- a/include/clang/Basic/SourceManager.h
+++ b/include/clang/Basic/SourceManager.h
@@ -17,21 +17,68 @@
 #include "clang/Basic/SourceLocation.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/System/DataTypes.h"
+#include "llvm/ADT/PointerUnion.h"
 #include "llvm/ADT/DenseMap.h"
 #include <vector>
 #include <cassert>
 
 namespace llvm {
 class MemoryBuffer;
+class StringRef;
 }
 
 namespace clang {
 
+class Diagnostic;
 class SourceManager;
 class FileManager;
 class FileEntry;
 class LineTableInfo;
-
+  
+/// \brief Class used as a return value by operations that return an
+/// \c llvm::MemoryBuffer.
+///
+/// Since not all source-manager routines that return buffers are guaranteed
+/// to succeed, 
+class BufferResult {
+  struct FailureData;
+  llvm::PointerUnion<const llvm::MemoryBuffer *, FailureData *> Data;
+  
+  // Cannot copy buffer result structures
+  BufferResult &operator=(const BufferResult &Other);
+  
+public:
+  BufferResult(const BufferResult &Other);
+  BufferResult(const llvm::MemoryBuffer *Buffer) : Data(Buffer) { }
+  BufferResult(const char *FileName, llvm::StringRef ErrorStr,
+               const llvm::MemoryBuffer *Buffer = 0);
+  ~BufferResult();
+  
+  // \brief Determine whether there was any failure when finding this buffer.
+  bool isInvalid() const;
+  
+  /// \brief Retrieve the memory buffer that this result refers to. If an
+  /// error occurs, emits a diagnostic via the given diagnostics object and
+  /// may return NULL.
+  const llvm::MemoryBuffer *getBuffer(Diagnostic &Diags) const;
+  
+  /// \brief Retrieve the memory buffer that this result refers to. If an error
+  /// occurs, provides the file name and a non-empty error string to indicate 
+  /// what failed, and may return NULL.
+  const llvm::MemoryBuffer *getBuffer(llvm::StringRef &FileName, 
+                                      std::string &Error) const;
+  
+  // FIXME: TEMPORARY! Allows a buffer result to be interpreted as a buffer,
+  // which is very unsafe (but is used throughout Clang). Note that this will
+  // spit a diagnostic to standard error before returning the buffer.
+  operator const llvm::MemoryBuffer *() const;
+  
+  // FIXME: TEMPORARY! Allows a buffer result to be interpreted like a smart
+  // pointer to a buffer, which is very unsafe. Note that this will emit a
+  // diagnostic to standard error before returning the buffer.
+  const llvm::MemoryBuffer * operator->() const { return *this; }
+};
+  
 /// SrcMgr - Public enums and private classes that are part of the
 /// SourceManager implementation.
 ///
@@ -68,10 +115,8 @@ namespace SrcMgr {
     /// if SourceLineCache is non-null.
     unsigned NumLines;
 
-    /// getBuffer - Returns the memory buffer for the associated content.  If
-    /// there is an error opening this buffer the first time, this manufactures
-    /// a temporary buffer and returns a non-empty error string.
-    const llvm::MemoryBuffer *getBuffer(std::string *ErrorStr = 0) const;
+    /// getBuffer - Returns the memory buffer for the associated content. 
+    BufferResult getBuffer() const;
 
     /// getSize - Returns the size of the content encapsulated by this
     ///  ContentCache. This can be the size of the source file or the size of an
@@ -407,7 +452,7 @@ public:
                                         unsigned Offset = 0);
 
   /// \brief Retrieve the memory buffer associated with the given file.
-  const llvm::MemoryBuffer *getMemoryBufferForFile(const FileEntry *File);
+  BufferResult getMemoryBufferForFile(const FileEntry *File);
 
   /// \brief Override the contents of the given source file by providing an
   /// already-allocated buffer.
@@ -428,8 +473,8 @@ public:
   /// getBuffer - Return the buffer for the specified FileID. If there is an
   /// error opening this buffer the first time, this manufactures a temporary
   /// buffer and returns a non-empty error string.
-  const llvm::MemoryBuffer *getBuffer(FileID FID, std::string *Error = 0) const{
-    return getSLocEntry(FID).getFile().getContentCache()->getBuffer(Error);
+  BufferResult getBuffer(FileID FID) const{
+    return getSLocEntry(FID).getFile().getContentCache()->getBuffer();
   }
 
   /// getFileEntryForID - Returns the FileEntry record for the provided FileID.
@@ -439,8 +484,21 @@ public:
 
   /// getBufferData - Return a pointer to the start and end of the source buffer
   /// data for the specified FileID.
-  std::pair<const char*, const char*> getBufferData(FileID FID) const;
+  ///
+  /// If an error occurs while reading in the file, provides the file name 
+  /// and a non-empty error string and returns a pair of NULL pointers.
+  std::pair<const char*, const char*> getBufferData(FileID FID,
+                                                    llvm::StringRef &FileName,
+                                                    std::string &Error) const;
 
+  /// getBufferData - Return a pointer to the start and end of the source buffer
+  /// data for the specified FileID.
+  /// 
+  /// If an error occurs while reading in the file, emits a diagnostic to the
+  /// given \c Diagnostic object and returns a pair of NULL pointers.
+  std::pair<const char*, const char*> getBufferData(FileID FID, 
+                                                    Diagnostic &Diags) const;
+  
 
   //===--------------------------------------------------------------------===//
   // SourceLocation manipulation methods.