From: Daniel Dunbar <daniel@zuster.org>
Date: Mon, 18 May 2009 17:30:52 +0000 (+0000)
Subject: Avoid potential out-of-bounds access in SourceManager::getLineNumber.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=4106d696d7d0725fcd442fdda28a07049d47c573;p=clang

Avoid potential out-of-bounds access in SourceManager::getLineNumber.
 - Chris, please see added FIXMEs.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@72019 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Basic/SourceManager.cpp b/lib/Basic/SourceManager.cpp
index 9ca00f5823..7d2d0ae172 100644
--- a/lib/Basic/SourceManager.cpp
+++ b/lib/Basic/SourceManager.cpp
@@ -729,11 +729,22 @@ unsigned SourceManager::getLineNumber(FileID FID, unsigned FilePos) const {
   
   unsigned QueriedFilePos = FilePos+1;
 
+  // FIXME: I would like to be convinced that this code is worth being as
+  // complicated as it is, binary search isn't that slow. 
+  //
+  // If it is worth being optimized, then in my opinion it could be more
+  // performant, simpler, and more obviously correct by just "galloping" outward
+  // from the queried file position. In fact, this could be incorporated into a
+  // generic algorithm such as lower_bound_with_hint.
+  //
+  // If someone gives me a test case where this matters, and I will do it! - DWD
+
   // If the previous query was to the same file, we know both the file pos from
   // that query and the line number returned.  This allows us to narrow the
   // search space from the entire file to something near the match.
   if (LastLineNoFileIDQuery == FID) {
     if (QueriedFilePos >= LastLineNoFilePos) {
+      // FIXME: Potential overflow?
       SourceLineCache = SourceLineCache+LastLineNoResult-1;
       
       // The query is likely to be nearby the previous one.  Here we check to
@@ -753,7 +764,8 @@ unsigned SourceManager::getLineNumber(FileID FID, unsigned FilePos) const {
         }
       }
     } else {
-      SourceLineCacheEnd = SourceLineCache+LastLineNoResult+1;
+      if (LastLineNoResult < Content->NumLines)
+        SourceLineCacheEnd = SourceLineCache+LastLineNoResult+1;
     }
   }