Auto merge of #50841 - oli-obk:promote_errors_to_panics, r=eddyb

Don't lint numeric overflows in promoteds in release mode

r? @eddyb

mitigates #50814

Author: bors

src/librustc_codegen_llvm/mir/operand.rs

@@ -413,10 +413,10 @@ impl<'a, 'tcx> FunctionCx<'a, 'tcx> {
                     .unwrap_or_else(|err| {
                         match constant.literal {
                             mir::Literal::Promoted { .. } => {
-                                // don't report errors inside promoteds, just warnings.
+                                // FIXME: generate a panic here
                             },
                             mir::Literal::Value { .. } => {
-                                err.report(bx.tcx(), constant.span, "const operand")
+                                err.report(bx.tcx(), constant.span, "const operand");
                             },
                         }
                         // We've errored, so we don't have to produce working code.

src/librustc_mir/interpret/eval_context.rs

@@ -521,21 +521,13 @@ impl<'a, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> EvalContext<'a, 'mir, 'tcx, M
             BinaryOp(bin_op, ref left, ref right) => {
                 let left = self.eval_operand(left)?;
                 let right = self.eval_operand(right)?;
-                if self.intrinsic_overflowing(
+                self.intrinsic_overflowing(
                     bin_op,
                     left,
                     right,
                     dest,
                     dest_ty,
-                )?
-                {
-                    // There was an overflow in an unchecked binop.  Right now, we consider this an error and bail out.
-                    // The rationale is that the reason rustc emits unchecked binops in release mode (vs. the checked binops
-                    // it emits in debug mode) is performance, but it doesn't cost us any performance in miri.
-                    // If, however, the compiler ever starts transforming unchecked intrinsics into unchecked binops,
-                    // we have to go back to just ignoring the overflow here.
-                    return err!(Overflow(bin_op));
-                }
+                )?;
             }
 
             CheckedBinaryOp(bin_op, ref left, ref right) => {

src/test/run-fail/promoted_div_by_zero.rs

@@ -0,0 +1,17 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(const_err)]
+
+// error-pattern: attempt to divide by zero
+
+fn main() {
+    let x = &(1 / (1 - 1));
+}

src/test/run-fail/promoted_overflow.rs

@@ -0,0 +1,18 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(const_err)]
+
+// error-pattern: overflow
+// compile-flags: -C overflow-checks=yes
+
+fn main() {
+    let x: &'static u32 = &(0u32 - 1);
+}

src/test/run-pass/promoted_overflow_opt.rs

@@ -0,0 +1,18 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(const_err)]
+
+// compile-flags: -O
+
+fn main() {
+    let x = &(0u32 - 1);
+    assert_eq!(*x, u32::max_value())
+}

src/test/ui/const-eval/promoted_const_fn_fail.rs

@@ -0,0 +1,38 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(const_fn)]
+
+#![deny(const_err)]
+
+union Bar {
+    a: &'static u8,
+    b: usize,
+}
+
+const fn bar() -> u8 {
+    unsafe {
+        // this will error as long as this test
+        // is run on a system whose pointers need more
+        // than 8 bits
+        Bar { a: &42 }.b as u8
+        //~^ constant evaluation error
+        //~| constant evaluation error
+    }
+}
+
+fn main() {
+    // FIXME(oli-obk): this should compile but panic at runtime
+    // if we change the `const_err` lint to allow this will actually compile, but then
+    // continue with undefined values.
+    let x: &'static u8 = &(bar() + 1);
+    let y = *x;
+    unreachable!();
+}

src/test/ui/const-eval/promoted_const_fn_fail.stderr

@@ -0,0 +1,31 @@
+error: constant evaluation error
+  --> $DIR/promoted_const_fn_fail.rs:25:9
+   |
+LL |         Bar { a: &42 }.b as u8
+   |         ^^^^^^^^^^^^^^^^^^^^^^ a raw memory access tried to access part of a pointer value as raw bytes
+   |
+note: lint level defined here
+  --> $DIR/promoted_const_fn_fail.rs:13:9
+   |
+LL | #![deny(const_err)]
+   |         ^^^^^^^^^
+note: inside call to `bar`
+  --> $DIR/promoted_const_fn_fail.rs:35:28
+   |
+LL |     let x: &'static u8 = &(bar() + 1);
+   |                            ^^^^^
+
+error: constant evaluation error
+  --> $DIR/promoted_const_fn_fail.rs:25:9
+   |
+LL |         Bar { a: &42 }.b as u8
+   |         ^^^^^^^^^^^^^^^^^^^^^^ a raw memory access tried to access part of a pointer value as raw bytes
+   |
+note: inside call to `bar`
+  --> $DIR/promoted_const_fn_fail.rs:35:28
+   |
+LL |     let x: &'static u8 = &(bar() + 1);
+   |                            ^^^^^
+
+error: aborting due to 2 previous errors
+

src/test/ui/const-eval/promoted_errors.rs

@@ -14,8 +14,6 @@
 // compile-flags: -O
 fn main() {
     println!("{}", 0u32 - 1);
-    //~^ WARN const_err
-    //~| WARN const_err
     let _x = 0u32 - 1;
     //~^ WARN const_err
     println!("{}", 1/(1-1));

src/test/ui/const-eval/promoted_errors.stderr

@@ -1,53 +1,41 @@
 warning: constant evaluation error
-  --> $DIR/promoted_errors.rs:16:20
+  --> $DIR/promoted_errors.rs:17:14
    |
-LL |     println!("{}", 0u32 - 1);
-   |                    ^^^^^^^^ attempt to subtract with overflow
+LL |     let _x = 0u32 - 1;
+   |              ^^^^^^^^ attempt to subtract with overflow
    |
 note: lint level defined here
   --> $DIR/promoted_errors.rs:11:9
    |
 LL | #![warn(const_err)]
    |         ^^^^^^^^^
 
-warning: constant evaluation error
-  --> $DIR/promoted_errors.rs:16:20
-   |
-LL |     println!("{}", 0u32 - 1);
-   |                    ^^^^^^^^ attempt to subtract with overflow
-
-warning: constant evaluation error
-  --> $DIR/promoted_errors.rs:19:14
-   |
-LL |     let _x = 0u32 - 1;
-   |              ^^^^^^^^ attempt to subtract with overflow
-
 warning: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:21:20
+  --> $DIR/promoted_errors.rs:19:20
    |
 LL |     println!("{}", 1/(1-1));
    |                    ^^^^^^^
 
 warning: constant evaluation error
-  --> $DIR/promoted_errors.rs:21:20
+  --> $DIR/promoted_errors.rs:19:20
    |
 LL |     println!("{}", 1/(1-1));
    |                    ^^^^^^^ attempt to divide by zero
 
 warning: attempt to divide by zero
-  --> $DIR/promoted_errors.rs:24:14
+  --> $DIR/promoted_errors.rs:22:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^
 
 warning: constant evaluation error
-  --> $DIR/promoted_errors.rs:24:14
+  --> $DIR/promoted_errors.rs:22:14
    |
 LL |     let _x = 1/(1-1);
    |              ^^^^^^^ attempt to divide by zero
 
 warning: constant evaluation error
-  --> $DIR/promoted_errors.rs:27:20
+  --> $DIR/promoted_errors.rs:25:20
    |
 LL |     println!("{}", 1/(false as u32));
    |                    ^^^^^^^^^^^^^^^^ attempt to divide by zero