[PATCH] D155523: [clang] Fix a crash when casting to an array type

[Alan Zhao via Phabricator via cfe-commits]

ayzhao created this revision.
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In C++20, if Clang fails to perform constructor overload on a
RecordType, then Clang will try to perform parentesized aggregate
initialization. If that fails and the initialization was attempted as
part of a cast, then we should get the diagnostics from the failed
constructor overload attempt. However, we don't attempt constructor
overloading for arrays, so previously, if we try to diagnose an
overloaded cast for a parenthesized aggregate initialization of an
array, we crash. To fix this, we now exit tryDiagnoseOverloadedCast(...)
for failed parentesized list initialization if the destination type is
an array.

Fixes #63758


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D155523

Files:
  clang/docs/ReleaseNotes.rst
  clang/lib/Sema/SemaCast.cpp
  clang/test/SemaCXX/paren-list-agg-init.cpp


Index: clang/test/SemaCXX/paren-list-agg-init.cpp
===================================================================
--- clang/test/SemaCXX/paren-list-agg-init.cpp
+++ clang/test/SemaCXX/paren-list-agg-init.cpp
@@ -294,3 +294,8 @@
 }
 
 }
+
+namespace gh63758 {
+  struct S {} s;
+  auto words = (char[])s; // expected-error {{C-style cast from 'struct S' to 'char[]' is not allowed}}
+};
Index: clang/lib/Sema/SemaCast.cpp
===================================================================
--- clang/lib/Sema/SemaCast.cpp
+++ clang/lib/Sema/SemaCast.cpp
@@ -454,9 +454,18 @@
   switch (sequence.getFailureKind()) {
   default: return false;
 
+  case InitializationSequence::FK_ParenthesizedListInitFailed:
+    // In C++20, if the underlying destination type is a RecordType, then we
+    // attempt to perform parentesized aggregate initialization if constructor
+    // overload fails. If that fails, then we'll generate the diagnostics from
+    // the failed overload result from the previous constructor overload. Array
+    // initialization, however, is not done after attempting constructor
+    // overloading, so we bail out as there won't be a failed overload result.
+    if (destType->isArrayType())
+      return false;
+    break;
   case InitializationSequence::FK_ConstructorOverloadFailed:
   case InitializationSequence::FK_UserConversionOverloadFailed:
-  case InitializationSequence::FK_ParenthesizedListInitFailed:
     break;
   }
 
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -634,6 +634,8 @@
   that construct (`#62133 <https://github.com/llvm/llvm-project/issues/38717>_`).
 - Fix crash caused by PseudoObjectExprBitfields: NumSubExprs overflow.
   (`#63169 <https://github.com/llvm/llvm-project/issues/63169>_`)
+- Fix crash when casting an object to an array type.
+  (`#63758 <https://github.com/llvm/llvm-project/issues/63758>_`)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


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