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Compiler crash pattern matching unsized tuple in enum variant #37685

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CasualX opened this issue Nov 10, 2016 · 6 comments
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Compiler crash pattern matching unsized tuple in enum variant #37685

CasualX opened this issue Nov 10, 2016 · 6 comments
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A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) C-bug Category: This is a bug. I-crash Issue: The compiler crashes (SIGSEGV, SIGABRT, etc). Use I-ICE instead when the compiler panics.

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@CasualX
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CasualX commented Nov 10, 2016 •
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I was trying to get an enum which owns some String or Vec<u8> be able to deref into an unsized enum whose variants have str or [u8] but this appears to be unsupported at the moment.

But I am persistent so I try to make the variants hold refs to their original owners but one of them is a tuple.

I found plenty of issues where tuples are also not allowed to have their tail unsized (which seems odd as tuple structs are perfectly fine having their last member unsized) but I tried it anyway in the context of an enum variant tuple.

I tried this code: playground

enum FooRef<'a> {
    A(&'a (str,))
}

fn foo(f: FooRef) {
    match f {
        FooRef::A(&(ref s,)) => (),
    }
}

fn main() {}

I expected to see this happen: A sane error about tuples not being allowed to have an unsized tail.

Instead, this happened: mysterious exit (error: Could not compile ... without any further explanation) with error code 3221225477. On the playground this results in Segmentation fault (core dumped).

As I wrote this I found out that the above example only breaks in Debug builds, Release builds print Program ended. on any Rust version on the playground.

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rustc 1.12.0 (3191fbae9 2016-09-23)
binary: rustc
commit-hash: 3191fbae9da539442351f883bdabcad0d72efcb6
commit-date: 2016-09-23
host: x86_64-pc-windows-msvc
release: 1.12.0
@CasualX
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CasualX commented Nov 10, 2016

So 322122547 in hex is 0xC0000005 which is the windows error code for access violation :)

@TimNN TimNN added the I-crash Issue: The compiler crashes (SIGSEGV, SIGABRT, etc). Use I-ICE instead when the compiler panics. label Nov 10, 2016
@TimNN
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TimNN commented Nov 10, 2016 •
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For me this happens only when compiling with debuginfo, backtrace:

#0  0x00007ffff1cec8e0 in LLVMTypeOf () from /home/logic/.multirust/toolchains/nightly-2016-11-06-x86_64-unknown-linux-gnu/bin/../lib/librustc_llvm-6eb85298.so
#1  0x00007ffff635336f in rustc_trans::common::val_ty () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/common.rs:708
#2  rustc_trans::base::from_immediate () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/base.rs:635
#3  0x00007ffff63c53d2 in rustc_trans::mir::MirContext::store_operand_direct ()
    at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/mir/operand.rs:269
#4  0x00007ffff63c5888 in rustc_trans::mir::operand::{{impl}}::store_operand::{{closure}} ()
    at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/mir/operand.rs:250
#5  rustc_trans::common::BlockAndBuilder::with_block<closure,()> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/common.rs:565
#6  rustc_trans::mir::MirContext::store_operand () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/mir/operand.rs:250
#7  rustc_trans::mir::MirContext::trans_rvalue () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/mir/rvalue.rs:181
#8  0x00007ffff63b4be1 in rustc_trans::mir::MirContext::trans_statement ()
    at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/mir/statement.rs:36
#9  rustc_trans::mir::MirContext::trans_block () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/mir/block.rs:104
#10 0x00007ffff63b3217 in rustc_trans::mir::trans_mir () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/mir/mod.rs:302
#11 0x00007ffff635715b in rustc_trans::base::trans_closure () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/base.rs:1040
#12 0x00007ffff63d1ece in rustc_trans::base::trans_instance () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/base.rs:1060
#13 rustc_trans::trans_item::TransItem::define () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/trans_item.rs:85
#14 0x00007ffff635a44c in rustc_trans::base::trans_crate::{{closure}} () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/base.rs:1636
#15 rustc::dep_graph::graph::DepGraph::with_task<closure,()> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc/dep_graph/graph.rs:77
#16 rustc_trans::base::trans_crate () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_trans/base.rs:1634
#17 0x00007ffff7b3e8d2 in rustc_driver::driver::phase_4_translate_to_llvm::{{closure}} ()
    at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/driver.rs:1025
#18 rustc::util::common::time<rustc_trans::CrateTranslation,closure> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc/util/common.rs:38
#19 rustc_driver::driver::phase_4_translate_to_llvm () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/driver.rs:1023
#20 0x00007ffff7b75ba1 in rustc_driver::driver::compile_input::{{closure}} ()
    at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/driver.rs:205
#21 0x00007ffff7b6809f in rustc_driver::driver::phase_3_run_analysis_passes::{{closure}}<closure,core::result::Result<(rustc::session::config::OutputFilenames, rustc_trans::CrateTranslation), usize>> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/driver.rs:979
#22 0x00007ffff7b32cb1 in rustc::ty::context::tls::enter::{{closure}}<closure,core::result::Result<core::result::Result<(rustc::session::config::OutputFilenames, rustc_trans::CrateTranslation), usize>, usize>> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc/ty/context.rs:966
#23 std::thread::local::LocalKey<core::cell::Cell<core::option::Option<(*const rustc::ty::context::tls::ThreadLocalGlobalCtxt, *const rustc::ty::context::tls::ThreadLocalInterners)>>>::with<core::cell::Cell<core::option::Option<(*const rustc::ty::context::tls::ThreadLocalGlobalCtxt, *const rustc::ty::context::tls::ThreadLocalInterners)>>,closure,core::result::Result<core::result::Result<(rustc::session::config::OutputFilenames, rustc_trans::CrateTranslation), usize>, usize>> ()
    at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/thread/local.rs:245
#24 rustc::ty::context::tls::enter<closure,core::result::Result<core::result::Result<(rustc::session::config::OutputFilenames, rustc_trans::CrateTranslation), usize>, usize>> ()
    at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc/ty/context.rs:963
#25 rustc::ty::context::tls::enter_global::{{closure}}<closure,core::result::Result<core::result::Result<(rustc::session::config::OutputFilenames, rustc_trans::CrateTranslation), usize>, usize>> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc/ty/context.rs:950
#26 std::thread::local::LocalKey<core::cell::Cell<fn(syntax_pos::Span, &mut core::fmt::Formatter) -> core::result::Result<(), core::fmt::Error>>>::with<core::cell::Cell<fn(syntax_pos::Span, &mut core::fmt::Formatter) -> core::result::Result<(), core::fmt::Error>>,closure,core::result::Result<core::result::Result<(rustc::session::config::OutputFilenames, rustc_trans::CrateTranslation), usize>, usize>> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/thread/local.rs:245
#27 rustc::ty::context::tls::enter_global<closure,core::result::Result<core::result::Result<(rustc::session::config::OutputFilenames, rustc_trans::CrateTranslation), usize>, usize>> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc/ty/context.rs:947
#28 rustc::ty::context::TyCtxt::create_and_enter<closure,core::result::Result<core::result::Result<(rustc::session::config::OutputFilenames, rustc_trans::CrateTranslation), usize>, usize>> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc/ty/context.rs:735
#29 rustc_driver::driver::phase_3_run_analysis_passes<closure,core::result::Result<(rustc::session::config::OutputFilenames, rustc_trans::CrateTranslation), usize>> ()
    at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/driver.rs:854
#30 0x00007ffff7b25505 in rustc_driver::driver::compile_input () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/driver.rs:172
#31 0x00007ffff7b4f6a1 in rustc_driver::run_compiler () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/lib.rs:222
#32 0x00007ffff7a8ebd9 in rustc_driver::main::{{closure}} () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/lib.rs:1138
#33 rustc_driver::run::{{closure}}<closure> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/lib.rs:138
#34 rustc_driver::monitor::{{closure}}<closure> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/librustc_driver/lib.rs:1072
#35 std::panic::{{impl}}::call_once<(),closure> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/panic.rs:295
#36 std::panicking::try::do_call<std::panic::AssertUnwindSafe<closure>,()> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/panicking.rs:356
#37 0x00007ffff77bc8ab in panic_unwind::__rust_maybe_catch_panic () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libpanic_unwind/lib.rs:97
#38 0x00007ffff7aad569 in std::panicking::try<(),std::panic::AssertUnwindSafe<closure>> ()
    at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/panicking.rs:332
#39 std::panic::catch_unwind<std::panic::AssertUnwindSafe<closure>,()> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/panic.rs:351
#40 std::thread::{{impl}}::spawn::{{closure}}<closure,()> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/thread/mod.rs:287
#41 alloc::boxed::{{impl}}::call_box<(),closure> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/liballoc/boxed.rs:595
#42 0x00007ffff77b04c5 in alloc::boxed::{{impl}}::call_once<(),()> () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/liballoc/boxed.rs:605
#43 std::sys_common::thread::start_thread () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/sys_common/thread.rs:21
#44 std::sys::imp::thread::{{impl}}::new::thread_start () at /buildslave/rust-buildbot/slave/nightly-dist-rustc-linux/build/obj/../src/libstd/sys/unix/thread.rs:84
#45 0x00007fffefa6f70a in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#46 0x00007ffff746f0af in clone () from /lib/x86_64-linux-gnu/libc.so.6

@TimNN TimNN added the A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) label Nov 10, 2016
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TimNN commented Nov 10, 2016

From a gdb session of a RelWithDbg build of llvm, the argument LLVMTypeOf(LLVMValueRef Val) is 0.

cc @michaelwoerister

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TimNN commented Nov 10, 2016

It seems as if the second value of an OperandRef(Pair(a, b)) is 0:

DEBUG:rustc_trans::mir::rvalue: trans_rvalue(dest.llval=(%FooRef*:  %f = alloca %FooRef), rvalue=_1)
DEBUG:rustc_trans::mir::operand: trans_operand(operand=_1)
DEBUG:rustc_trans::mir::operand: trans_consume(lvalue=_1)
DEBUG:rustc_trans::mir::operand: trans_load: (%FooRef*:  %arg0 = alloca %FooRef) @ FooRef
DEBUG:rustc_trans::mir::operand: store_operand: operand=OperandRef(Immediate((%FooRef = type { { i8 }* }:  %4 = load %FooRef, %FooRef* %arg0, !dbg !41)) @ FooRef)
DEBUG:rustc_trans::mir::rvalue: trans_rvalue(dest.llval=(%str_slice*:  %s = alloca %str_slice), rvalue=&((*(_2.0: &(str,))).0: str))
DEBUG:rustc_trans::mir::operand: trans_consume(lvalue=(_2.0: &(str,)))
DEBUG:rustc_trans::mir::operand: trans_load: ({ i8 }**:  %5 = getelementptr inbounds %FooRef, %FooRef* %f, i32 0, i32 0, !dbg !42) @ &(str,)
DEBUG:rustc_trans::mir::operand: store_operand: operand=OperandRef(Pair((i8*:  %7 = getelementptr inbounds { i8 }, { i8 }* %6, i32 0, i32 0, !dbg !42),
rustc: /home/logic/build-tmp/rust-build/build/x86_64-unknown-linux-gnu/llvm/include/llvm/Support/Casting.h:95: static bool llvm::isa_impl_cl<To, const From*>::doit(const From*) [with To = llvm::Value; From = llvm::Value]: Assertion `Val && "isa<> used on a null pointer"' failed.
Aborted

@eddyb
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eddyb commented Nov 12, 2016

Unsized tuples are simply not supported, although they have never been properly banned. Trans is likely to crash and burn instead.

cc @rust-lang/lang @rust-lang/compiler

This was referenced Jun 4, 2017
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@qnighy qnighy mentioned this issue Jun 24, 2017
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bors added a commit that referenced this issue Jun 29, 2017
@bors
Auto merge of #42527 - qnighy:unsized-tuple-coercions, r=arielb1
686ec28 
Unsized tuple coercions

Part of #18469. Fixes #32702.

#37685 and #34451 might also be related.

This PR does the following:

- Introduce explicit `Sized` constraints on tuple initializers, similar to that of record-struct initializers. Not much relevant to the main contribution but I noticed this when making tests for unsized tuple coercions.
- Implement `(.., T): Unsize<(.., U)>` where `T: Unsize<U>`.
- Assume `(.., T)` is MaybeUnsizedUnivariant.
- Modify `src/librustc/ty/util.rs` and `src/librustc_trans/glue.rs` so that tuples and structs are uniformly traversed when translating.
@Mark-Simulacrum Mark-Simulacrum added the C-bug Category: This is a bug. label Jul 26, 2017
@matthiaskrgr matthiaskrgr mentioned this issue Feb 25, 2018
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@CasualX
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CasualX commented Sep 10, 2018 •
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This issue looks resolved? I can no longer reproduce the ICE in my example in the playground.

@oli-obk oli-obk closed this as completed Jan 15, 2019
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A-debuginfo Area: Debugging information in compiled programs (DWARF, PDB, etc.) C-bug Category: This is a bug. I-crash Issue: The compiler crashes (SIGSEGV, SIGABRT, etc). Use I-ICE instead when the compiler panics.
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