Author: rnk
Date: Thu Oct 20 15:53:20 2016
New Revision: 284777
URL: http://llvm.org/viewvc/llvm-project?rev=284777&view=rev
Log:
Fix off-by-one error in PPCaching.cpp token annotation assertion
This assert is intended to defend against backtracking into the middle
of a sequence of tokens that is being replaced with an annotation, but
it's OK if we backtrack to the exact position of the start of the
annotation sequence. Use a <= comparison instead of <.
Fixes PR25946
Added:
cfe/trunk/test/Parser/backtrack-off-by-one.cpp
Modified:
cfe/trunk/lib/Lex/PPCaching.cpp
Modified: cfe/trunk/lib/Lex/PPCaching.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Lex/PPCaching.cpp?rev=284777&r1=284776&r2=284777&view=diff
==============================================================================
--- cfe/trunk/lib/Lex/PPCaching.cpp (original)
+++ cfe/trunk/lib/Lex/PPCaching.cpp Thu Oct 20 15:53:20 2016
@@ -105,7 +105,7 @@ void Preprocessor::AnnotatePreviousCache
for (CachedTokensTy::size_type i = CachedLexPos; i != 0; --i) {
CachedTokensTy::iterator AnnotBegin = CachedTokens.begin() + i-1;
if (AnnotBegin->getLocation() == Tok.getLocation()) {
- assert((BacktrackPositions.empty() || BacktrackPositions.back() < i) &&
+ assert((BacktrackPositions.empty() || BacktrackPositions.back() <= i) &&
"The backtrack pos points inside the annotated tokens!");
// Replace the cached tokens with the single annotation token.
if (i < CachedLexPos)
Added: cfe/trunk/test/Parser/backtrack-off-by-one.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/backtrack-off-by-one.cpp?rev=284777&view=auto
==============================================================================
--- cfe/trunk/test/Parser/backtrack-off-by-one.cpp (added)
+++ cfe/trunk/test/Parser/backtrack-off-by-one.cpp Thu Oct 20 15:53:20 2016
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -verify %s
+
+// PR25946
+// We had an off-by-one error in an assertion when annotating A<int> below.
Our
+// error recovery checks if A<int> is a constructor declarator, and opens a
+// TentativeParsingAction. Then we attempt to annotate the token at the exact
+// position that we want to possibly backtrack to, and this used to crash.
+
+template <typename T> class A {};
+
+// expected-error@+1 {{expected '{' after base class list}}
+template <typename T> class B : T // not ',' or '{'
+// expected-error@+3 {{C++ requires a type specifier for all declarations}}
+// expected-error@+2 {{expected ';' after top level declarator}}
+// expected-error@+1 {{expected ';' after class}}
+A<int> {
+};
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