[all-commits] [llvm/llvm-project] 4417a7: [ExprConstant] Treat `&*p` as not a dereference in...

[Akira Hatanaka via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4417a7501aae8a9b8d3ffee1d491540a0858cc29
      https://github.com/llvm/llvm-project/commit/4417a7501aae8a9b8d3ffee1d491540a0858cc29
  Author: Akira Hatanaka <ahatanak at gmail.com>
  Date:   2026-06-05 (Fri, 05 Jun 2026)

  Changed paths:
    M clang/lib/AST/ByteCode/Compiler.cpp
    M clang/lib/AST/ExprConstant.cpp
    M clang/test/Sema/static-init.c

  Log Message:
  -----------
  [ExprConstant] Treat `&*p` as not a dereference in C constant initializers (#201483)

In C, [C11 6.5.3.2p3] specifies that when the operand of unary `&` is
the result of a unary `*` operator, neither operator is evaluated and
the result is as if both were omitted. So `&*p` yields the pointer value
`p` without performing a dereference, and forming it is well-defined
even when `p` is null (e.g. `&*(int *)0`).

The constant evaluator did not honor this: it evaluated the `*` as a
real lvalue access and diagnosed a null dereference as undefined
behavior. This went unnoticed for ordinary scalar initializers, which
use the relaxed `Expr::isConstantInitializer()` check, but a bit-field
initializer is evaluated via `EvaluateAsInt()` with `SE_NoSideEffects`,
so the same expression was rejected there with "initializer element is
not a compile-time constant":

```
  struct S { long v : 8; };
  const struct S s = { .v = (long)&*(int *)0 };   // error
  const long x     = (long)&*(int *)0;            // accepted
```

Handle `&*p` in `PointerExprEvaluator::VisitUnaryAddrOf` (and the
corresponding `UO_AddrOf` case in the bytecode interpreter) by
evaluating the pointer operand directly in C.

Fixes #197846.

rdar://158774335



To unsubscribe from these emails, change your notification settings at https://github.com/llvm/llvm-project/settings/notifications