[Clang] Fix incorrect use of direct initialization with copy initialization

[shafik]

Summary

In Sema::CreateBuiltinBinOp() we were incorrectly using direct initialization instead of copy initialization. This led to a crash in a copy initialization case with an enum with a fixed underlying type.

see dcl.init.general p14

This fixes: https://github.com/llvm/llvm-project/issues/62503

[shafik]

It looks like the build failure happens on other PR as well.

[shafik]

ping

[cor3ntin]

LGTM but can you add a line in Release Notes? Thanks

clang/test/CXX/dcl.decl/dcl.init/dcl.init.list/p3.cpp

292

Should we add a test that passes here? Even if it currently doesn't crash

enum class E {Foo};
E e;
e = {E::Foo};

[shafik]

• Added release note
• Added test case

[rsmith]

clang/lib/Sema/SemaExpr.cpp

15441–15443

The code change doesn't match this comment, which says we should use direct non-list initialization. Though the comment is slightly wrong / out of date: the standard text now says:

"an assignment to a scalar, in which case the initializer list shall have at most a single element. The meaning of x = {v}, where T is the scalar type of the expression x, is that of x = T{v}. The meaning of x = {} is x = T{}."

... which says to use direct list initialization to create a temporary in the scalar type case.

[rsmith]

clang/test/CXX/dcl.decl/dcl.init/dcl.init.list/p3.cpp

293

This looks valid to me. The language rules say we treat this as e = E{0};, which we accept.

[shafik]

clang/test/CXX/dcl.decl/dcl.init/dcl.init.list/p3.cpp

292

Sure that makes sense, more coverage is good.

293

Richard and I discussed this and I agree that based on http://eel.is/c++draft/expr.ass#8.1 this should be the same as e = E{0} and this would be direct init and we should accept this.

clang/docs/ReleaseNotes.rst

 - Fix C++17 mode assert when parsing malformed code and the compiler is
   attempting to see if it could be type template for class template argument
   deduction. This fixes
   (`Issue 57495 <https://github.com/llvm/llvm-project/issues/57495>`_)
 - Fix missing destructor calls and therefore memory leaks in generated code
   when an immediate invocation appears as a part of an expression that produces
   temporaries.
   (`#60709 <https://github.com/llvm/llvm-project/issues/60709>`_).
+- Fix use of direct-intialization over copy-initialization when using
+  = form of brace-or-equal-initialzer. This fixes
+  (`#63503 <https://github.com/llvm/llvm-project/issues/62503>`_).
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Bug Fixes to Attribute Support
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 - Fixed a bug where attribute annotations on type specifiers (enums, classes,
   structs, unions, and scoped enums) were not properly ignored, resulting in

clang/lib/Sema/SemaExpr.cpp

 /// built-in operations; ActOnBinOp handles overloaded operators.
 ExprResult Sema::CreateBuiltinBinOp(SourceLocation OpLoc,
                                     BinaryOperatorKind Opc,
                                     Expr *LHSExpr, Expr *RHSExpr) {
   if (getLangOpts().CPlusPlus11 && isa<InitListExpr>(RHSExpr)) {
     // The syntax only allows initializer lists on the RHS of assignment,
     // so we don't need to worry about accepting invalid code for
     // non-assignment operators.
     // C++11 5.17p9:
     //   The meaning of x = {v} [...] is that of x = T(v) [...]. The meaning
     //   of x = {} is x = T().
-    InitializationKind Kind = InitializationKind::CreateDirectList(
-        RHSExpr->getBeginLoc(), RHSExpr->getBeginLoc(), RHSExpr->getEndLoc());
+    InitializationKind Kind =
+        InitializationKind::CreateCopy(RHSExpr->getBeginLoc(), OpLoc);
     InitializedEntity Entity =
         InitializedEntity::InitializeTemporary(LHSExpr->getType());
     InitializationSequence InitSeq(*this, Entity, Kind, RHSExpr);
     ExprResult Init = InitSeq.Perform(*this, Entity, Kind, RHSExpr);
     if (Init.isInvalid())
       return Init;
     RHSExpr = Init.get();
   }

clang/test/CXX/dcl.decl/dcl.init/dcl.init.list/p3.cpp

 #if __cplusplus > 201402L
   enum class F : unsigned {};
   F f1(unsigned x) { return F{x}; }
   F f2(const unsigned x) { return F{x}; }
   F f3(bool x) { return F{x}; }
   F f4(const bool x) { return F{x}; }
 #endif
 }
+
+namespace GH62503 {
+enum class E {E1};
+
+void f() {
+  E e;
+  e = {E::E1};
+  e = {0}; // expected-error {{cannot initialize a value of type 'E' with an rvalue of type 'int'}}
+}
+}