Allow nested backtracks.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@55204 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/Lex/Preprocessor.h b/include/clang/Lex/Preprocessor.h
index 786af69..1f9fc44 100644
--- a/include/clang/Lex/Preprocessor.h
+++ b/include/clang/Lex/Preprocessor.h
@@ -155,10 +155,11 @@
/// a normal Lex() should be invoked.
CachedTokensTy::size_type CachedLexPos;
- /// CachedBacktrackPos - Gets set by the EnableBacktrackAtThisPos() method,
- /// to indicate the position where CachedLexPos should be set when the
- /// BackTrack() method is invoked.
- CachedTokensTy::size_type CachedBacktrackPos;
+ /// BacktrackPositions - Stack of backtrack positions, allowing nested
+ /// backtracks. The EnableBacktrackAtThisPos() method pushes a position to
+ /// indicate where CachedLexPos should be set when the BackTrack() method is
+ /// invoked (at which point the last position is popped).
+ std::vector<CachedTokensTy::size_type> BacktrackPositions;
public:
Preprocessor(Diagnostic &diags, const LangOptions &opts, TargetInfo &target,
@@ -281,34 +282,22 @@
/// track of the lexed tokens so that a subsequent Backtrack() call will make
/// the Preprocessor re-lex the same tokens.
///
- /// EnableBacktrackAtThisPos should not be called again until DisableBacktrack
- /// or Backtrack is called.
+ /// Nested backtracks are allowed, meaning that EnableBacktrackAtThisPos can
+ /// be called multiple times and DisableBacktrack/Backtrack calls will be
+ /// combined with the EnableBacktrackAtThisPos calls in reverse order.
///
/// NOTE: *DO NOT* forget to call either DisableBacktrack() or Backtrack() at
/// some point after EnableBacktrackAtThisPos. If you don't, caching of tokens
/// will continue indefinitely.
///
- void EnableBacktrackAtThisPos() {
- assert(!CacheTokens && "Backtrack is already enabled!");
- CacheTokens = true;
- CachedBacktrackPos = CachedLexPos;
- EnterCachingLexMode();
- }
+ void EnableBacktrackAtThisPos();
- /// DisableBacktrack - Stop the caching of tokens that was enabled by
- /// EnableBacktrackAtThisPos().
- void DisableBacktrack() {
- assert(CacheTokens && "Backtrack is not enabled!");
- CacheTokens = false;
- }
+ /// DisableBacktrack - Disable the last EnableBacktrackAtThisPos() call.
+ void DisableBacktrack();
/// Backtrack - Make Preprocessor re-lex the tokens that were lexed since
/// EnableBacktrackAtThisPos() was previously called.
- void Backtrack() {
- assert(CacheTokens && "Backtrack is not enabled!");
- CacheTokens = false;
- CachedLexPos = CachedBacktrackPos;
- }
+ void Backtrack();
/// isBacktrackEnabled - True if EnableBacktrackAtThisPos() was called and
/// caching of tokens is on.
diff --git a/lib/Lex/PPCaching.cpp b/lib/Lex/PPCaching.cpp
index 794e9c4..e69eac6 100644
--- a/lib/Lex/PPCaching.cpp
+++ b/lib/Lex/PPCaching.cpp
@@ -15,6 +15,38 @@
#include "clang/Lex/Preprocessor.h"
using namespace clang;
+/// EnableBacktrackAtThisPos - From the point that this method is called, and
+/// until DisableBacktrack() or Backtrack() is called, the Preprocessor keeps
+/// track of the lexed tokens so that a subsequent Backtrack() call will make
+/// the Preprocessor re-lex the same tokens.
+///
+/// Nested backtracks are allowed, meaning that EnableBacktrackAtThisPos can
+/// be called multiple times and DisableBacktrack/Backtrack calls will be
+/// combined with the EnableBacktrackAtThisPos calls in reverse order.
+void Preprocessor::EnableBacktrackAtThisPos() {
+ CacheTokens = true;
+ BacktrackPositions.push_back(CachedLexPos);
+ EnterCachingLexMode();
+}
+
+/// DisableBacktrack - Disable the last EnableBacktrackAtThisPos() call.
+void Preprocessor::DisableBacktrack() {
+ assert(!BacktrackPositions.empty()
+ && "EnableBacktrackAtThisPos was not called!");
+ BacktrackPositions.pop_back();
+ CacheTokens = !BacktrackPositions.empty();
+}
+
+/// Backtrack - Make Preprocessor re-lex the tokens that were lexed since
+/// EnableBacktrackAtThisPos() was previously called.
+void Preprocessor::Backtrack() {
+ assert(!BacktrackPositions.empty()
+ && "EnableBacktrackAtThisPos was not called!");
+ CachedLexPos = BacktrackPositions.back();
+ BacktrackPositions.pop_back();
+ CacheTokens = !BacktrackPositions.empty();
+}
+
void Preprocessor::CachingLex(Token &Result) {
if (CachedLexPos < CachedTokens.size()) {
Result = CachedTokens[CachedLexPos++];