[clang] 55f1b91 - [Clang] Fix a crash when parsing an invalid `decltype` (#148798)

[via cfe-commits]

Author: Corentin Jabot
Date: 2025-07-15T18:09:51+02:00
New Revision: 55f1b91d50a0f3706ad62d497d3c8a5ec572d59e

URL: https://github.com/llvm/llvm-project/commit/55f1b91d50a0f3706ad62d497d3c8a5ec572d59e
DIFF: https://github.com/llvm/llvm-project/commit/55f1b91d50a0f3706ad62d497d3c8a5ec572d59e.diff

LOG: [Clang] Fix a crash when parsing an invalid `decltype` (#148798)

We would try to exact an annotated token before checking if it was
valid, leading to a crash when `decltype` was the only token that was
parsed (which can happen in the absense of opening paren)

Fixes #114815

Added: 
    clang/test/Parser/gh114815.cpp

Modified: 
    clang/lib/Parse/ParseDeclCXX.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 9fe18b0dbcedb..9cae4f9a23ef0 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -1133,13 +1133,6 @@ void Parser::AnnotateExistingDecltypeSpecifier(const DeclSpec &DS,
   // make sure we have a token we can turn into an annotation token
   if (PP.isBacktrackEnabled()) {
     PP.RevertCachedTokens(1);
-    if (DS.getTypeSpecType() == TST_error) {
-      // We encountered an error in parsing 'decltype(...)' so lets annotate all
-      // the tokens in the backtracking cache - that we likely had to skip over
-      // to get to a token that allows us to resume parsing, such as a
-      // semi-colon.
-      EndLoc = PP.getLastCachedTokenLocation();
-    }
   } else
     PP.EnterToken(Tok, /*IsReinject*/ true);
 

diff  --git a/clang/test/Parser/gh114815.cpp b/clang/test/Parser/gh114815.cpp
new file mode 100644
index 0000000000000..6a89384e9e66d
--- /dev/null
+++ b/clang/test/Parser/gh114815.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -verify %s -std=c++11 -fsyntax-only
+
+#define ID(X) X
+extern int ID(decltype);
+// expected-error at -1 {{expected '(' after 'decltype'}} \
+// expected-error at -1 {{expected unqualified-id}}