[clang] [clang] Check null TypeSourceInfo in CreateUnaryExprOrTypeTraitExpr (PR #112111)

[Andrew Sukach via cfe-commits]

https://github.com/sookach created https://github.com/llvm/llvm-project/pull/112111

Fixes #111594. The crash is caused by the following call
https://github.com/llvm/llvm-project/blob/main/clang/lib/AST/ComputeDependence.cpp#L81-L82

We already check for a null TypeInfo when creating a UnaryExprOrTypeTraitExpr here
https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/SemaExpr.cpp#L4616-L4617

but the following lines can, and in the case of the code in the issue, nullify the TypeInfo
https://github.com/llvm/llvm-project/blob/main/clang/lib/Sema/SemaExpr.cpp#L4616-L4617

Thus, adding the additional check for nullptr prevents the erroneous memory access.

@shafik Thoughts? Thanks


>From 215a126137ef43bbb24abbd5c0847744d2a4d083 Mon Sep 17 00:00:00 2001
From: Andrew Sukach <andrewsukach at gmail.com>
Date: Sat, 12 Oct 2024 19:47:30 -0400
Subject: [PATCH] [clang] Check for null TypeSourceInfo in
 Sema::CreateUnaryExprOrTypeTraitExpr

---
 clang/lib/Sema/SemaExpr.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 4e37385710af5e..b0bd216c5dc101 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -4629,6 +4629,9 @@ ExprResult Sema::CreateUnaryExprOrTypeTraitExpr(TypeSourceInfo *TInfo,
       TInfo->getType()->isVariablyModifiedType())
     TInfo = TransformToPotentiallyEvaluated(TInfo);
 
+  if (!TInfo)
+    return ExprError();
+
   // C99 6.5.3.4p4: the type (an unsigned integer type) is size_t.
   return new (Context) UnaryExprOrTypeTraitExpr(
       ExprKind, TInfo, Context.getSizeType(), OpLoc, R.getEnd());