[clang] [clang][ExprConst] Check for array size of initlists (PR #138673)

[Timm Baeder via cfe-commits]

https://github.com/tbaederr updated https://github.com/llvm/llvm-project/pull/138673

>From 224ff74f7cd2460414c96e8b528e8f086535da5f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Tue, 6 May 2025 12:36:24 +0200
Subject: [PATCH] [clang][ExprConst] Check for array size of initlists

Fixes #138653
---
 clang/lib/AST/ExprConstant.cpp                | 10 +++++++
 .../SemaCXX/constant-expression-cxx2a.cpp     | 28 +++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index e5950f461e4b2..63a94a7855a49 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -11788,6 +11788,11 @@ bool ArrayExprEvaluator::VisitCXXParenListOrInitListExpr(
   LLVM_DEBUG(llvm::dbgs() << "The number of elements to initialize: "
                           << NumEltsToInit << ".\n");
 
+  if (!Info.CheckArraySize(ExprToVisit->getExprLoc(),
+                           CAT->getNumAddressingBits(Info.Ctx), NumEltsToInit,
+                           /*Diag=*/true))
+    return false;
+
   Result = APValue(APValue::UninitArray(), NumEltsToInit, NumElts);
 
   // If the array was previously zero-initialized, preserve the
@@ -11919,6 +11924,11 @@ bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E,
   if (const ConstantArrayType *CAT = Info.Ctx.getAsConstantArrayType(Type)) {
     unsigned FinalSize = CAT->getZExtSize();
 
+    if (!Info.CheckArraySize(E->getExprLoc(),
+                             CAT->getNumAddressingBits(Info.Ctx), FinalSize,
+                             /*Diag=*/true))
+      return false;
+
     // Preserve the array filler if we had prior zero-initialization.
     APValue Filler =
       HadZeroInit && Value->hasArrayFiller() ? Value->getArrayFiller()
diff --git a/clang/test/SemaCXX/constant-expression-cxx2a.cpp b/clang/test/SemaCXX/constant-expression-cxx2a.cpp
index 85720606fe9de..d65651d195b3b 100644
--- a/clang/test/SemaCXX/constant-expression-cxx2a.cpp
+++ b/clang/test/SemaCXX/constant-expression-cxx2a.cpp
@@ -1497,3 +1497,31 @@ namespace GH67317 {
                               // expected-note {{subobject of type 'const unsigned char' is not initialized}}
     __builtin_bit_cast(unsigned char, *new char[3][1]);
 };
+
+namespace LargeArrays {
+  constexpr unsigned kNumberOfIterations = 2000000;
+  constexpr unsigned kThreadsNumber = 2 * 8 * 1024;
+
+  /// Large array initialized by Paren/InitListExpr.
+  template <typename T, unsigned long S>
+  struct array1 {
+    using AT = T[S];
+    AT Data{};
+    constexpr array1() : Data(T()) {}
+  };
+
+  /// And initialized by a CXXConstructExpr.
+  template <typename T, unsigned long S>
+  struct array2 {
+    using AT = T[S];
+    AT Data;
+    constexpr array2() {}
+  };
+
+  template <typename T>
+  class A{};
+  int main() {
+      array1<A<short*>, kThreadsNumber * kNumberOfIterations> futures1{};
+      array2<A<short*>, kThreadsNumber * kNumberOfIterations> futures2{};
+  }
+}