llvm: Stored value type does not match pointer operand type!

[yorkie]

Hey Rust Team,

I got this error at compiling time:

Stored value type does not match pointer operand type!
  store { i64 } %0, i64* %2, align 8
 i64LLVM ERROR: Broken function found, compilation aborted!
Could not compile `rustjs`.

Caused by:
  Process didn't exit successfully: `rustc src/lib.rs --crate-name rustjs --crate-type lib -g --out-dir /Users/yorkieliu/workspace/rust.js/target/debug --emit=dep-info,link -L dependency=/Users/yorkieliu/workspace/rust.js/target/debug -L dependency=/Users/yorkieliu/workspace/rust.js/target/debug/deps --extern clap=/Users/yorkieliu/workspace/rust.js/target/debug/deps/libclap-b681d5dfd49166f9.rlib --extern rustc_serialize=/Users/yorkieliu/workspace/rust.js/target/debug/deps/librustc_serialize-3c33cb2a40992011.rlib --extern libc=/Users/yorkieliu/workspace/rust.js/target/debug/deps/liblibc-dd3420cb049117bb.rlib --extern env_logger=/Users/yorkieliu/workspace/rust.js/target/debug/deps/libenv_logger-2fedde90a22290a6.rlib -l rustjs_deps` (exit code: 1)
make: *** [rustjs] Error 101

With my personal rust module: https://github.com/yorkie/rust.js, I found the same issue at #19571.

I used the latest 1.5.0, however it worked at 1.0.0.

[eddyb]

This seems unrelated to #19571.
Can you try other versions? If your code compiles on them, that is.
If you have multirust, it should be trivial to switch between versions.

I could try to reduce rust.js myself, it looks like a moderately sized project.

[eddyb]

Minimal reproduction:

struct Foo;
impl Foo {
    extern fn foo(_: [u8; 1]) {}
}

It appears that extern methods (not free functions) have their arguments incorrectly translated.
cc @dotdash @Aatch

[yorkie]

Thanks @eddyb for that so detailed reply, do you think it's related to this commit yorkie/rust.js@9525af0?

[eddyb]

No, not really.
The problem stems from the fact that you're passing structures by value in arguments, e.g.:

#[repr(C)]
pub struct FunctionCallbackInfo(*mut *mut FunctionCallbackInfo);

...

impl StringBytes {
  extern fn New(arguments: v8::FunctionCallbackInfo) {
    arguments.GetReturnValue().SetWithBool(true);
  }
}

One way you might be able to work around this bug would be to remove one level of indirection, e.g.

extern {
  fn v8_function_callback_info_get_return_value(this: &mut FunctionCallbackInfo) -> &mut ReturnValue;
}

// Doesn't really matter what's inside, can still pretend there's a pointer there.
#[repr(C)]
pub struct FunctionCallbackInfo(*mut u8);
#[repr(C)]
pub struct ReturnValue(*mut u8);

impl FunctionCallbackInfo {
  pub fn GetReturnValue(&mut self) -> &mut ReturnValue {
    unsafe { v8_function_callback_info_get_return_value(self) }
  }
}

impl StringBytes {
  extern fn New(arguments: &mut v8::FunctionCallbackInfo) {
    arguments.GetReturnValue().SetWithBool(true);
  }
}

And on the C++ side:

ReturnValue<Value> v8_function_callback_info_get_return_value(FunctionCallbackInfo<Value> *callbackInfo) {
  return callbackInfo->GetReturnValue();
}

It would be a pretty big change, but it should make your code compile.

[eddyb]

@yorkie Sorry, I was overthinking this, you should be able to get away with just moving extern fn methods out of impl blocks (and make them free functions).

This issue is also related to #30235.

[arielb1]

duplicate of #30235.