From a9f9145b094188d1915138385cb4dc8c8656090c Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sun, 28 Aug 2022 13:13:13 -0400 Subject: [PATCH] CTFE: exposing pointers and calling extern fn doesn't need an RFC, it is just impossible --- compiler/rustc_const_eval/src/const_eval/machine.rs | 8 +++++--- compiler/rustc_const_eval/src/interpret/machine.rs | 1 + src/test/ui/consts/miri_unleashed/ptr_arith.rs | 2 +- src/test/ui/consts/miri_unleashed/ptr_arith.stderr | 2 +- 4 files changed, 8 insertions(+), 5 deletions(-) diff --git a/compiler/rustc_const_eval/src/const_eval/machine.rs b/compiler/rustc_const_eval/src/const_eval/machine.rs index 6c1e61fccca..55b5bbc7065 100644 --- a/compiler/rustc_const_eval/src/const_eval/machine.rs +++ b/compiler/rustc_const_eval/src/const_eval/machine.rs @@ -269,9 +269,10 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir, ); throw_inval!(AlreadyReported(guar)); } else { + // `find_mir_or_eval_fn` checks that this is a const fn before even calling us, + // so this should be unreachable. let path = ecx.tcx.def_path_str(def.did); - Err(ConstEvalErrKind::NeedsRfc(format!("calling extern function `{}`", path)) - .into()) + bug!("trying to call extern function `{path}` at compile-time"); } } _ => Ok(ecx.tcx.instance_mir(instance)), @@ -469,7 +470,8 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir, _ecx: &mut InterpCx<'mir, 'tcx, Self>, _ptr: Pointer, ) -> InterpResult<'tcx> { - Err(ConstEvalErrKind::NeedsRfc("exposing pointers".to_string()).into()) + // This is only reachable with -Zunleash-the-miri-inside-of-you. + throw_unsup_format!("exposing pointers is not possible at compile-time") } #[inline(always)] diff --git a/compiler/rustc_const_eval/src/interpret/machine.rs b/compiler/rustc_const_eval/src/interpret/machine.rs index 6bed8a7a007..8df6737b839 100644 --- a/compiler/rustc_const_eval/src/interpret/machine.rs +++ b/compiler/rustc_const_eval/src/interpret/machine.rs @@ -490,6 +490,7 @@ pub macro compile_time_machine(<$mir: lifetime, $tcx: lifetime>) { ) -> InterpResult<$tcx, Pointer>> { // Allow these casts, but make the pointer not dereferenceable. // (I.e., they behave like transmutation.) + // This is correct because no pointers can ever be exposed in compile-time evaluation. Ok(Pointer::from_addr(addr)) } diff --git a/src/test/ui/consts/miri_unleashed/ptr_arith.rs b/src/test/ui/consts/miri_unleashed/ptr_arith.rs index 13e6af36e02..2d5cb9b6834 100644 --- a/src/test/ui/consts/miri_unleashed/ptr_arith.rs +++ b/src/test/ui/consts/miri_unleashed/ptr_arith.rs @@ -8,7 +8,7 @@ static PTR_INT_CAST: () = { let x = &0 as *const _ as usize; //~^ ERROR could not evaluate static initializer - //~| "exposing pointers" needs an rfc before being allowed inside constants + //~| exposing pointers let _v = x == x; }; diff --git a/src/test/ui/consts/miri_unleashed/ptr_arith.stderr b/src/test/ui/consts/miri_unleashed/ptr_arith.stderr index 00cff23fb3f..f5c5ee2b8eb 100644 --- a/src/test/ui/consts/miri_unleashed/ptr_arith.stderr +++ b/src/test/ui/consts/miri_unleashed/ptr_arith.stderr @@ -2,7 +2,7 @@ error[E0080]: could not evaluate static initializer --> $DIR/ptr_arith.rs:9:13 | LL | let x = &0 as *const _ as usize; - | ^^^^^^^^^^^^^^^^^^^^^^^ "exposing pointers" needs an rfc before being allowed inside constants + | ^^^^^^^^^^^^^^^^^^^^^^^ exposing pointers is not possible at compile-time error[E0080]: could not evaluate static initializer --> $DIR/ptr_arith.rs:17:14