1 files changed, 11 insertions, 0 deletions
diff --git a/clang/lib/Lex/Pragma.cpp b/clang/lib/Lex/Pragma.cpp
index 100da514144..f81eaa31e9e 100644
--- a/clang/lib/Lex/Pragma.cpp
+++ b/clang/lib/Lex/Pragma.cpp
@@ -160,12 +160,23 @@ public:
 
   ~LexingFor_PragmaRAII() {
     if (InMacroArgPreExpansion) {
+      // When committing/backtracking the cached pragma tokens in a macro
+      // argument pre-expansion we want to ensure that either the tokens which
+      // have been committed will be removed from the cache or that the tokens
+      // over which we just backtracked won't remain in the cache after they're
+      // consumed and that the caching will stop after consuming them.
+      // Otherwise the caching will interfere with the way macro expansion
+      // works, because we will continue to cache tokens after consuming the
+      // backtracked tokens, which shouldn't happen when we're dealing with
+      // macro argument pre-expansion.
+      auto CachedTokenRange = PP.LastCachedTokenRange();
       if (Failed) {
         PP.CommitBacktrackedTokens();
       } else {
         PP.Backtrack();
         OutTok = PragmaTok;
       }
+      PP.EraseCachedTokens(CachedTokenRange);
     }
   }