From 0294e3f98b17fe6e13df55ac360e990eb92360d4 Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sun, 20 Dec 2020 20:02:27 +0100 Subject: [PATCH 1/3] WIP crater experiment: do not promote const fn calls implicitly ever --- compiler/rustc_mir/src/transform/promote_consts.rs | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/compiler/rustc_mir/src/transform/promote_consts.rs b/compiler/rustc_mir/src/transform/promote_consts.rs index 8d5ed747c3f8f..5e3f215d24bc3 100644 --- a/compiler/rustc_mir/src/transform/promote_consts.rs +++ b/compiler/rustc_mir/src/transform/promote_consts.rs @@ -692,14 +692,9 @@ impl<'tcx> Validator<'_, 'tcx> { ) -> Result<(), Unpromotable> { let fn_ty = callee.ty(self.body, self.tcx); - // When doing explicit promotion and inside const/static items, we promote all (eligible) function calls. + // When doing explicit promotion, we promote all (eligible) function calls. // Everywhere else, we require `#[rustc_promotable]` on the callee. - let promote_all_const_fn = self.explicit - || matches!( - self.const_kind, - Some(hir::ConstContext::Static(_) | hir::ConstContext::Const) - ); - if !promote_all_const_fn { + if !self.explicit { if let ty::FnDef(def_id, _) = *fn_ty.kind() { // Never promote runtime `const fn` calls of // functions without `#[rustc_promotable]`. From 76240d7d1cf16cc0900b1fe7f689cca8bc07b28b Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Mon, 28 Dec 2020 21:48:11 +0100 Subject: [PATCH 2/3] make some functions promotable to reduce fallout --- library/core/src/ptr/const_ptr.rs | 1 + library/core/src/ptr/mod.rs | 4 ++-- library/core/src/ptr/mut_ptr.rs | 1 + library/core/src/slice/mod.rs | 2 ++ library/std/src/net/ip.rs | 2 ++ 5 files changed, 8 insertions(+), 2 deletions(-) diff --git a/library/core/src/ptr/const_ptr.rs b/library/core/src/ptr/const_ptr.rs index 8fd9ff768c4f4..729dd90315e81 100644 --- a/library/core/src/ptr/const_ptr.rs +++ b/library/core/src/ptr/const_ptr.rs @@ -43,6 +43,7 @@ impl *const T { /// Casts to a pointer of another type. #[stable(feature = "ptr_cast", since = "1.38.0")] #[rustc_const_stable(feature = "const_ptr_cast", since = "1.38.0")] + #[rustc_promotable] // Operation cannot fail, so it may be promoted. #[inline] pub const fn cast(self) -> *const U { self as _ diff --git a/library/core/src/ptr/mod.rs b/library/core/src/ptr/mod.rs index 27d49529a5ec2..b683fa0f3c8b8 100644 --- a/library/core/src/ptr/mod.rs +++ b/library/core/src/ptr/mod.rs @@ -196,7 +196,7 @@ pub unsafe fn drop_in_place(to_drop: *mut T) { /// ``` #[inline(always)] #[stable(feature = "rust1", since = "1.0.0")] -#[rustc_promotable] +#[rustc_promotable] // Operation cannot fail, so it may be promoted. #[rustc_const_stable(feature = "const_ptr_null", since = "1.32.0")] pub const fn null() -> *const T { 0 as *const T @@ -214,7 +214,7 @@ pub const fn null() -> *const T { /// ``` #[inline(always)] #[stable(feature = "rust1", since = "1.0.0")] -#[rustc_promotable] +#[rustc_promotable] // Operation cannot fail, so it may be promoted. #[rustc_const_stable(feature = "const_ptr_null", since = "1.32.0")] pub const fn null_mut() -> *mut T { 0 as *mut T diff --git a/library/core/src/ptr/mut_ptr.rs b/library/core/src/ptr/mut_ptr.rs index 5f94c2393aef3..78222a198cc78 100644 --- a/library/core/src/ptr/mut_ptr.rs +++ b/library/core/src/ptr/mut_ptr.rs @@ -42,6 +42,7 @@ impl *mut T { /// Casts to a pointer of another type. #[stable(feature = "ptr_cast", since = "1.38.0")] #[rustc_const_stable(feature = "const_ptr_cast", since = "1.38.0")] + #[rustc_promotable] // Operation cannot fail, so it may be promoted. #[inline] pub const fn cast(self) -> *mut U { self as _ diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs index f5af48e0dd277..91ce9a40f33d7 100644 --- a/library/core/src/slice/mod.rs +++ b/library/core/src/slice/mod.rs @@ -404,6 +404,7 @@ impl [T] { /// [`as_mut_ptr`]: #method.as_mut_ptr #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_stable(feature = "const_slice_as_ptr", since = "1.32.0")] + #[rustc_promotable] // Operation cannot fail, so it may be promoted. #[inline] pub const fn as_ptr(&self) -> *const T { self as *const [T] as *const T @@ -432,6 +433,7 @@ impl [T] { /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[rustc_const_unstable(feature = "const_ptr_offset", issue = "71499")] + #[rustc_promotable] // Operation cannot fail, so it may be promoted. #[inline] pub const fn as_mut_ptr(&mut self) -> *mut T { self as *mut [T] as *mut T diff --git a/library/std/src/net/ip.rs b/library/std/src/net/ip.rs index d33b772633d29..b13e435bd8842 100644 --- a/library/std/src/net/ip.rs +++ b/library/std/src/net/ip.rs @@ -302,6 +302,7 @@ impl Ipv4Addr { /// let addr = Ipv4Addr::new(127, 0, 0, 1); /// ``` #[rustc_const_stable(feature = "const_ipv4", since = "1.32.0")] + #[rustc_promotable] // Operation cannot fail, so it may be promoted. #[stable(feature = "rust1", since = "1.0.0")] pub const fn new(a: u8, b: u8, c: u8, d: u8) -> Ipv4Addr { // `s_addr` is stored as BE on all machine and the array is in BE order. @@ -1045,6 +1046,7 @@ impl Ipv6Addr { /// ``` #[rustc_allow_const_fn_unstable(const_fn_transmute)] #[rustc_const_stable(feature = "const_ipv6", since = "1.32.0")] + #[rustc_promotable] // Operation cannot fail, so it may be promoted. #[stable(feature = "rust1", since = "1.0.0")] pub const fn new(a: u16, b: u16, c: u16, d: u16, e: u16, f: u16, g: u16, h: u16) -> Ipv6Addr { let addr16 = [ From 6a3a321e3121110a20ff4ac5eac001dd6c358145 Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Mon, 28 Dec 2020 23:17:41 +0100 Subject: [PATCH 3/3] update test suite --- src/test/ui/consts/const-eval/ub-ref.rs | 2 +- src/test/ui/consts/const-eval/ub-ref.stderr | 4 ++-- .../rfc-2203-const-array-repeat-exprs/fn-call-in-const.rs | 7 +++---- 3 files changed, 6 insertions(+), 7 deletions(-) diff --git a/src/test/ui/consts/const-eval/ub-ref.rs b/src/test/ui/consts/const-eval/ub-ref.rs index e8b101fed6d2f..bf812e6be0b1a 100644 --- a/src/test/ui/consts/const-eval/ub-ref.rs +++ b/src/test/ui/consts/const-eval/ub-ref.rs @@ -26,7 +26,7 @@ const REF_AS_USIZE: usize = unsafe { mem::transmute(&0) }; const REF_AS_USIZE_SLICE: &[usize] = &[unsafe { mem::transmute(&0) }]; //~^ ERROR it is undefined behavior to use this value -const REF_AS_USIZE_BOX_SLICE: Box<[usize]> = unsafe { mem::transmute::<&[usize], _>(&[mem::transmute(&0)]) }; +const REF_AS_USIZE_BOX_SLICE: Box<[usize]> = unsafe { mem::transmute(&[&0] as &[_]) }; //~^ ERROR it is undefined behavior to use this value const USIZE_AS_REF: &'static u8 = unsafe { mem::transmute(1337usize) }; diff --git a/src/test/ui/consts/const-eval/ub-ref.stderr b/src/test/ui/consts/const-eval/ub-ref.stderr index 429ae69eabfdb..17fe0c076403d 100644 --- a/src/test/ui/consts/const-eval/ub-ref.stderr +++ b/src/test/ui/consts/const-eval/ub-ref.stderr @@ -49,8 +49,8 @@ LL | const REF_AS_USIZE_SLICE: &[usize] = &[unsafe { mem::transmute(&0) }]; error[E0080]: it is undefined behavior to use this value --> $DIR/ub-ref.rs:29:1 | -LL | const REF_AS_USIZE_BOX_SLICE: Box<[usize]> = unsafe { mem::transmute::<&[usize], _>(&[mem::transmute(&0)]) }; - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at ., but expected plain (non-pointer) bytes +LL | const REF_AS_USIZE_BOX_SLICE: Box<[usize]> = unsafe { mem::transmute(&[&0] as &[_]) }; + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at ., but expected plain (non-pointer) bytes | = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior. diff --git a/src/test/ui/consts/rfc-2203-const-array-repeat-exprs/fn-call-in-const.rs b/src/test/ui/consts/rfc-2203-const-array-repeat-exprs/fn-call-in-const.rs index da1bae1be8d4e..6bc7ebbc28284 100644 --- a/src/test/ui/consts/rfc-2203-const-array-repeat-exprs/fn-call-in-const.rs +++ b/src/test/ui/consts/rfc-2203-const-array-repeat-exprs/fn-call-in-const.rs @@ -1,7 +1,8 @@ // run-pass -#![allow(unused)] +#![allow(unused, incomplete_features)] #![feature(const_in_array_repeat_expressions)] +#![feature(inline_const)] // Some type that is not copyable. struct Bar; @@ -16,8 +17,6 @@ const fn type_copy() -> u32 { const _: [u32; 2] = [type_copy(); 2]; -// This is allowed because all promotion contexts use the explicit rules for promotability when -// inside an explicit const context. -const _: [Option; 2] = [type_no_copy(); 2]; +const _: [Option; 2] = [const { type_no_copy() }; 2]; fn main() {}