LLVM assertion when calling std::mem::align_of() on recursive struct with fixed-size vec

[michaelwoerister]

Example program:

use std::mem;

struct AlignmentStruct {
    ptr: *mut [AlignmentStruct, ..1]
}

fn main() {
    println!("{}", ::std::mem::align_of::<AlignmentStruct>());
}

Error message:

rustc: /home/rustbuild/src/rust-buildbot/slave/nightly-linux/build/src/llvm/lib/IR/DataLayout.cpp:636: unsigned int llvm::DataLayout::getAlignment(llvm::Type*, bool) const: Assertion `Ty->isSized() && "Cannot getTypeInfo() on a type that is unsized!"' failed.

[DavidJFelix]

I just received this same error when using the following:

use std::rc::Rc;

struct Test {
    children: [Option<Rc<Test>>; 8],
}

impl Test {
    fn get_child() -> Option<Rc<Test>> {
        None
    }
}

I tried to reduce the code as much as possible and still get the error.

[tamird]

No longer ICEs. Both examples compile without error:

use std::mem;

struct AlignmentStruct {
    ptr: *mut [AlignmentStruct; 1]
}

fn main() {
    println!("{}", ::std::mem::align_of::<AlignmentStruct>());
}

use std::rc::Rc;

struct Test {
    children: [Option<Rc<Test>>; 8],
}

impl Test {
    fn get_child() -> Option<Rc<Test>> {
        None
    }
}

fn main() {
    // Add code here
}

[steveklabnik]

I get a strange error for the first:

hello.rs:1:5: 1:13 warning: unused import, #[warn(unused_imports)] on by default
hello.rs:1 use std::mem;
               ^~~~~~~~
hello.rs:4:9: 4:39 warning: struct field is never used: `ptr`, #[warn(dead_code)] on by default
hello.rs:4         ptr: *mut [AlignmentStruct; 1]
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
rustc: /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/lib/IR/DataLayout.cpp:655: unsigned int llvm::DataLayout::getAlignment(llvm::Type*, bool) const: Assertion `Ty->isSized() && "Cannot getTypeInfo() on a type that is unsized!"' failed.

hello.rs:1:5: 1:13 warning: unused import, #[warn(unused_imports)] on by default
hello.rs:1 use std::mem;
               ^~~~~~~~
hello.rs:4:9: 4:39 warning: struct field is never used: `ptr`, #[warn(dead_code)] on by default
hello.rs:4         ptr: *mut [AlignmentStruct; 1]
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
rustc: /home/rustbuild/src/rust-buildbot/slave/nightly-dist-rustc-linux/build/src/llvm/lib/IR/DataLayout.cpp:655: unsigned int llvm::DataLayout::getAlignment(llvm::Type*, bool) const: Assertion `Ty->isSized() && "Cannot getTypeInfo() on a type that is unsized!"' failed.

and the second both.

[tamird]

$ rustc --version
rustc 1.0.0-dev (f46c4e158 2015-04-20) (built 2015-04-20)

@steveklabnik what do you have?

[steveklabnik]

$ rustc --version
rustc 1.0.0-nightly (f46c4e158 2015-04-20) (built 2015-04-21)

[tamird]

@steveklabnik could yours have been built against a different LLVM version? cc @alexcrichton because I don't know how the buildbots do their thing

[steveklabnik]

I'm just doing whatever multirust installed.

[alexcrichton]

@tamird this probably has to do with LLVM assertions being disabled by default in nightly

[arielb1]

still an issue on 1.4.

[apasel422]

This appears to compile successfully now.

[dotdash]

Still hits an LLVM assertion with the latest nightly for me.

@apasel422 stable and beta builds have LLVM assertions disabled, so you can't reproduce with those.

[apasel422]

Hmm, I just built from source with LLVM assertions enabled and it appeared
to work.

On Monday, October 26, 2015, Björn Steinbrink [email protected]
wrote:

Still hits an LLVM assertion with the latest nightly for me.

@apasel422 https://github.com/apasel422 stable and beta builds have
LLVM assertions disabled, so you can't reproduce with those.

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Reply to this email directly or view it on GitHub
#19001 (comment).

[dotdash]

I'll try with a local build once it finished.

And I forgot to mention that only the second example given by @tamird still fails for me. The first one works fine.

[apasel422]

Yes, that example by @tamird continues to fail.