1 files changed, 26 insertions, 12 deletions

diff --git a/contrib/llvm/lib/Support/MemoryBuffer.cpp b/contrib/llvm/lib/Support/MemoryBuffer.cpp
index 0771af5..16e5c7a 100644
--- a/contrib/llvm/lib/Support/MemoryBuffer.cpp
+++ b/contrib/llvm/lib/Support/MemoryBuffer.cpp
@@ -14,6 +14,7 @@
 #include "llvm/Support/MemoryBuffer.h"
 #include "llvm/ADT/OwningPtr.h"
 #include "llvm/ADT/SmallString.h"
+#include "llvm/Config/config.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/Errno.h"
 #include "llvm/Support/Path.h"
@@ -29,15 +30,12 @@
 #include <sys/stat.h>
 #if !defined(_MSC_VER) && !defined(__MINGW32__)
 #include <unistd.h>
-#include <sys/uio.h>
 #else
 #include <io.h>
 #endif
 #include <fcntl.h>
 using namespace llvm;
 
-namespace { const llvm::error_code success; }
-
 //===----------------------------------------------------------------------===//
 // MemoryBuffer implementation itself.
 //===----------------------------------------------------------------------===//
@@ -306,7 +304,17 @@ error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
                                                       RealMapOffset)) {
       result.reset(GetNamedBuffer<MemoryBufferMMapFile>(
           StringRef(Pages + Delta, MapSize), Filename, RequiresNullTerminator));
-      return success;
+
+      if (RequiresNullTerminator && result->getBufferEnd()[0] != '\0') {
+        // There could be a racing issue that resulted in the file being larger
+        // than the FileSize passed by the caller. We already have an assertion
+        // for this in MemoryBuffer::init() but have a runtime guarantee that
+        // the buffer will be null-terminated here, so do a copy that adds a
+        // null-terminator.
+        result.reset(MemoryBuffer::getMemBufferCopy(result->getBuffer(),
+                                                    Filename));
+      }
+      return error_code::success();
     }
   }
 
@@ -321,29 +329,35 @@ error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
   char *BufPtr = const_cast<char*>(SB->getBufferStart());
 
   size_t BytesLeft = MapSize;
+#ifndef HAVE_PREAD
   if (lseek(FD, Offset, SEEK_SET) == -1)
     return error_code(errno, posix_category());
+#endif
 
   while (BytesLeft) {
+#ifdef HAVE_PREAD
+    ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);
+#else
     ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
+#endif
     if (NumRead == -1) {
       if (errno == EINTR)
         continue;
       // Error while reading.
       return error_code(errno, posix_category());
-    } else if (NumRead == 0) {
-      // We hit EOF early, truncate and terminate buffer.
-      Buf->BufferEnd = BufPtr;
-      *BufPtr = 0;
-      result.swap(SB);
-      return success;
+    }
+    if (NumRead == 0) {
+      assert(0 && "We got inaccurate FileSize value or fstat reported an "
+                   "invalid file size.");
+      *BufPtr = '\0'; // null-terminate at the actual size.
+      break;
     }
     BytesLeft -= NumRead;
     BufPtr += NumRead;
   }
 
   result.swap(SB);
-  return success;
+  return error_code::success();
 }
 
 //===----------------------------------------------------------------------===//
@@ -372,5 +386,5 @@ error_code MemoryBuffer::getSTDIN(OwningPtr<MemoryBuffer> &result) {
   } while (ReadBytes != 0);
 
   result.reset(getMemBufferCopy(Buffer, "<stdin>"));
-  return success;
+  return error_code::success();
 }