/
trans-tag-static-padding.rs
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/
trans-tag-static-padding.rs
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// 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.
// Issue #13186
// For simplicity of explanations assuming code is compiled for x86_64
// Linux ABI.
// Size of TestOption<u64> is 16, and alignment of TestOption<u64> is 8.
// Size of u8 is 1, and alignment of u8 is 1.
// So size of Request is 24, and alignment of Request must be 8:
// the maximum alignment of its fields.
// Last 7 bytes of Request struct are not occupied by any fields.
enum TestOption<T> {
TestNone,
TestSome(T),
}
pub struct Request {
foo: TestOption<u64>,
bar: u8,
}
fn default_instance() -> &'static Request {
static instance: Request = Request {
// LLVM does not allow to specify alignment of expressions, thus
// alignment of `foo` in constant is 1, not 8.
foo: TestNone,
bar: 17,
// Space after last field is not occupied by any data, but it is
// reserved to make struct aligned properly. If compiler does
// not insert padding after last field when emitting constant,
// size of struct may be not equal to size of struct, and
// compiler crashes in internal assertion check.
};
&'static instance
}
fn non_default_instance() -> &'static Request {
static instance: Request = Request {
foo: TestSome(0x1020304050607080),
bar: 19,
};
&'static instance
}
pub fn main() {
match default_instance() {
&Request { foo: TestNone, bar: 17 } => {},
_ => fail!(),
};
match non_default_instance() {
&Request { foo: TestSome(0x1020304050607080), bar: 19 } => {},
_ => fail!(),
};
}