1 files changed, 51 insertions, 1 deletions

diff --git a/lib/Bitcode/Reader/BitcodeReader.cpp b/lib/Bitcode/Reader/BitcodeReader.cpp
index 3fc6b17..a8c62be 100644
--- a/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -1184,6 +1184,47 @@ bool BitcodeReader::ParseModule(const std::string &ModuleID) {
   return Error("Premature end of bitstream");
 }
 
+/// SkipWrapperHeader - Some systems wrap bc files with a special header for
+/// padding or other reasons.  The format of this header is:
+///
+/// struct bc_header {
+///   uint32_t Magic;         // 0x0B17C0DE
+///   uint32_t Version;       // Version, currently always 0.
+///   uint32_t BitcodeOffset; // Offset to traditional bitcode file.
+///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
+///   ... potentially other gunk ...
+/// };
+/// 
+/// This function is called when we find a file with a matching magic number.
+/// In this case, skip down to the subsection of the file that is actually a BC
+/// file.
+static bool SkipWrapperHeader(unsigned char *&BufPtr, unsigned char *&BufEnd) {
+  enum {
+    KnownHeaderSize = 4*4,  // Size of header we read.
+    OffsetField = 2*4,      // Offset in bytes to Offset field.
+    SizeField = 3*4         // Offset in bytes to Size field.
+  };
+  
+  
+  // Must contain the header!
+  if (BufEnd-BufPtr < KnownHeaderSize) return true;
+  
+  unsigned Offset = ( BufPtr[OffsetField  ]        |
+                     (BufPtr[OffsetField+1] << 8)  |
+                     (BufPtr[OffsetField+2] << 16) |
+                     (BufPtr[OffsetField+3] << 24));
+  unsigned Size   = ( BufPtr[SizeField    ]        |
+                     (BufPtr[SizeField  +1] << 8)  |
+                     (BufPtr[SizeField  +2] << 16) |
+                     (BufPtr[SizeField  +3] << 24));
+  
+  // Verify that Offset+Size fits in the file.
+  if (Offset+Size > unsigned(BufEnd-BufPtr))
+    return true;
+  BufPtr += Offset;
+  BufEnd = BufPtr+Size;
+  return false;
+}
 
 bool BitcodeReader::ParseBitcode() {
   TheModule = 0;
@@ -1192,7 +1233,16 @@ bool BitcodeReader::ParseBitcode() {
     return Error("Bitcode stream should be a multiple of 4 bytes in length");
   
   unsigned char *BufPtr = (unsigned char *)Buffer->getBufferStart();
-  Stream.init(BufPtr, BufPtr+Buffer->getBufferSize());
+  unsigned char *BufEnd = BufPtr+Buffer->getBufferSize();
+  
+  // If we have a wrapper header, parse it and ignore the non-bc file contents.
+  // The magic number is 0x0B17C0DE stored in little endian.
+  if (BufPtr != BufEnd && BufPtr[0] == 0xDE && BufPtr[1] == 0xC0 && 
+      BufPtr[2] == 0x17 && BufPtr[3] == 0x0B)
+    if (SkipWrapperHeader(BufPtr, BufEnd))
+      return Error("Invalid bitcode wrapper header");
+  
+  Stream.init(BufPtr, BufEnd);
   
   // Sniff for the signature.
   if (Stream.Read(8) != 'B' ||