Embed the offset of the PTH table inside the prologue of the PTH file. This will help improve gradual versioning of PTH files instead of relying that the PTH table is at a fixed offset.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@63045 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 9 deletions

diff --git a/lib/Lex/PTHLexer.cpp b/lib/Lex/PTHLexer.cpp
index f6994e0976..747ec10156 100644
--- a/lib/Lex/PTHLexer.cpp
+++ b/lib/Lex/PTHLexer.cpp
@@ -520,17 +520,18 @@ PTHManager* PTHManager::Create(const std::string& file) {
   // words at the end of the file.
   const unsigned char* BufBeg = (unsigned char*)File->getBufferStart();
   const unsigned char* BufEnd = (unsigned char*)File->getBufferEnd();
-  
-  if(!(BufEnd > BufBeg + sizeof(uint32_t)*3)) {
-    assert(false && "Invalid PTH file.");
-    return 0; // FIXME: Proper error diagnostic?
-  }
+
+  // Check the prologue of the file.
+  if ((BufEnd - BufBeg) < (unsigned) (sizeof("cfe-pth") + 3) ||
+      memcmp(BufBeg, "cfe-pth", sizeof("cfe-pth") - 1) != 0)
+    return 0;
   
   // Compute the address of the index table at the end of the PTH file.
-  // This table contains the offset of the file lookup table, the
-  // persistent ID -> identifer data table.
-  // FIXME: We should just embed this offset in the PTH file.
-  const unsigned char* EndTable = BufEnd - sizeof(uint32_t)*4;
+  const unsigned char *p = BufBeg + (sizeof("cfe-pth") - 1);
+  const unsigned char *EndTable = BufBeg + ReadLE32(p);
+  
+  if (EndTable >= BufEnd)
+    return 0;
   
   // Construct the file lookup table.  This will be used for mapping from
   // FileEntry*'s to cached tokens.