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Revert "Remove the return_address intrinsic." #34580

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Jul 3, 2016
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6 changes: 6 additions & 0 deletions src/libcore/intrinsics.rs
Original file line number Diff line number Diff line change
Expand Up @@ -293,6 +293,12 @@ extern "rust-intrinsic" {
#[stable(feature = "rust1", since = "1.0.0")]
pub fn transmute<T, U>(e: T) -> U;

/// Gives the address for the return value of the enclosing function.
///
/// Using this intrinsic in a function that does not use an out pointer
/// will trigger a compiler error.
pub fn return_address() -> *const u8;

/// Returns `true` if the actual type given as `T` requires drop
/// glue; returns `false` if the actual type provided for `T`
/// implements `Copy`.
Expand Down
38 changes: 38 additions & 0 deletions src/librustc_trans/diagnostics.rs
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,44 @@

register_long_diagnostics! {

E0510: r##"
`return_address` was used in an invalid context. Erroneous code example:

```ignore
#![feature(intrinsics)]

extern "rust-intrinsic" {
fn return_address() -> *const u8;
}

unsafe fn by_value() -> i32 {
let _ = return_address();
// error: invalid use of `return_address` intrinsic: function does
// not use out pointer
0
}
```

Return values may be stored in a return register(s) or written into a so-called
out pointer. In case the returned value is too big (this is
target-ABI-dependent and generally not portable or future proof) to fit into
the return register(s), the compiler will return the value by writing it into
space allocated in the caller's stack frame. Example:

```
#![feature(intrinsics)]

extern "rust-intrinsic" {
fn return_address() -> *const u8;
}

unsafe fn by_pointer() -> String {
let _ = return_address();
String::new() // ok!
}
```
"##,

E0511: r##"
Invalid monomorphization of an intrinsic function was used. Erroneous code
example:
Expand Down
12 changes: 12 additions & 0 deletions src/librustc_trans/intrinsic.rs
Original file line number Diff line number Diff line change
Expand Up @@ -617,6 +617,18 @@ pub fn trans_intrinsic_call<'a, 'blk, 'tcx>(mut bcx: Block<'blk, 'tcx>,

},


(_, "return_address") => {
if !fcx.fn_ty.ret.is_indirect() {
span_err!(tcx.sess, span, E0510,
"invalid use of `return_address` intrinsic: function \
does not use out pointer");
C_null(Type::i8p(ccx))
} else {
PointerCast(bcx, llvm::get_param(fcx.llfn, 0), Type::i8p(ccx))
}
}

(_, "discriminant_value") => {
let val_ty = substs.types.get(FnSpace, 0);
match val_ty.sty {
Expand Down
2 changes: 2 additions & 0 deletions src/librustc_typeck/check/intrinsic.rs
Original file line number Diff line number Diff line change
Expand Up @@ -275,6 +275,8 @@ pub fn check_intrinsic_type(ccx: &CrateCtxt, it: &hir::ForeignItem) {
"fadd_fast" | "fsub_fast" | "fmul_fast" | "fdiv_fast" | "frem_fast" =>
(1, vec![param(ccx, 0), param(ccx, 0)], param(ccx, 0)),

"return_address" => (0, vec![], tcx.mk_imm_ptr(tcx.types.u8)),

"assume" => (0, vec![tcx.types.bool], tcx.mk_nil()),

"discriminant_value" => (1, vec![
Expand Down
24 changes: 24 additions & 0 deletions src/test/compile-fail/intrinsic-return-address.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,24 @@
// Copyright 2014 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(warnings)]
#![feature(intrinsics)]

extern "rust-intrinsic" {
fn return_address() -> *const u8;
}

unsafe fn f() { let _ = return_address(); }
//~^ ERROR invalid use of `return_address` intrinsic: function does not use out pointer

unsafe fn g() -> isize { let _ = return_address(); 0 }
//~^ ERROR invalid use of `return_address` intrinsic: function does not use out pointer

fn main() {}
43 changes: 43 additions & 0 deletions src/test/run-pass/intrinsic-return-address.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,43 @@
// Copyright 2012-2014 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(intrinsics)]

use std::ptr;

struct Point {
x: f32,
y: f32,
z: f32,
}

extern "rust-intrinsic" {
fn return_address() -> *const u8;
}

fn f(result: &mut usize) -> Point {
unsafe {
*result = return_address() as usize;
Point {
x: 1.0,
y: 2.0,
z: 3.0,
}
}

}

fn main() {
let mut intrinsic_reported_address = 0;
let pt = f(&mut intrinsic_reported_address);
let actual_address = &pt as *const Point as usize;
assert_eq!(intrinsic_reported_address, actual_address);
}