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fix static_ptr_ty for foreign statics #78101

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Merged
merged 3 commits into from
Oct 21, 2020
Merged

fix static_ptr_ty for foreign statics #78101

merged 3 commits into from
Oct 21, 2020

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RalfJung
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Cc #74840

This does not fix that issue but fixes a problem in static_ptr_ty that we noticed while discussing that issue. I also added and updated a few comments. The one about internal locals being ignored does not seem to have been true even in the commit that introduced it.

r? @oli-obk

@rust-highfive rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 19, 2020
@RalfJung
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However, the test suite currently fails with an ICE:

---- [ui] ui/threads-sendsync/thread-local-extern-static.rs stdout ----

error: test compilation failed although it shouldn't!
status: exit code: 101
command: "/home/r/src/rust/rustc.2/build/x86_64-unknown-linux-gnu/stage1/bin/rustc" "/home/r/src/rust/rustc.2/src/test/ui/threads-sendsync/thread-local-extern-static.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-C" "prefer-dynamic" "-o" "/home/r/src/rust/rustc.2/build/x86_64-unknown-linux-gnu/test/ui/threads-sendsync/thread-local-extern-static/a" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/home/r/src/rust/rustc.2/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/home/r/src/rust/rustc.2/build/x86_64-unknown-linux-gnu/test/ui/threads-sendsync/thread-local-extern-static/auxiliary"
stdout:
------------------------------------------

------------------------------------------
stderr:
------------------------------------------
error: internal compiler error: broken MIR in DefId(0:7 ~ thread_local_extern_static[317d]::main) (_6 = &/*tls*/ FOO): bad assignment (*const std::cell::Cell<u32> = &'static std::cell::Cell<u32>): NoSolution
  --> /home/r/src/rust/rustc.2/src/test/ui/threads-sendsync/thread-local-extern-static.rs:22:20
   |
LL |         assert_eq!(FOO.get(), 3);
   |                    ^^^
   |
   = note: delayed at compiler/rustc_mir/src/borrow_check/type_check/mod.rs:253:27

error: internal compiler error: broken MIR in Item(WithOptConstParam { did: DefId(0:7 ~ thread_local_extern_static[317d]::main), const_param_did: None }) (end of phase Optimization) at bb0[5]:
encountered `Assign((_5, &/*tls*/ FOO))` with incompatible types:
left-hand side has type: *const Cell<u32>
right-hand side has type: &'static Cell<u32>
  --> /home/r/src/rust/rustc.2/src/test/ui/threads-sendsync/thread-local-extern-static.rs:22:20
   |
LL |         assert_eq!(FOO.get(), 3);
   |                    ^^^
   |
   = note: delayed at compiler/rustc_mir/src/transform/validate.rs:156:36

Looks like something somewhere is not using static_ptr_ty to determine the type of a thread-local extern static and thus causes different types to be used on the two sides.

@RalfJung
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Or maybe it is the other way around -- convert_path_expr now uses raw pointers for extern thread-local refs but something else still expects that to be a normal reference. Thread-local refs have their own ExprKind and I don't know how that works.

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I think I found where the wrong type was coming from.

oli-obk
oli-obk reviewed Oct 20, 2020
View reviewed changes
compiler/rustc_middle/src/mir/tcx.rs
Comment on lines +155 to +162
let static_ty = tcx.type_of(did);
if tcx.is_mutable_static(did) {
tcx.mk_mut_ptr(tcx.type_of(did))
tcx.mk_mut_ptr(static_ty)
} else if tcx.is_foreign_item(did) {
tcx.mk_imm_ptr(static_ty)
} else {
tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.type_of(did))
// FIXME: These things don't *really* have 'static lifetime.
tcx.mk_imm_ref(tcx.lifetimes.re_static, static_ty)
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This could be deduplicated with the other site by putting it in a function. I see no danger in eagerly normalizing static items' types (so doing it here, too).

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@RalfJung RalfJung Oct 20, 2020 •
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I did that at first, but the lifetime differs. That lead to ICEs.

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uff, right

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oli-obk commented Oct 20, 2020

@bors r+

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bors commented Oct 20, 2020

📌 Commit 153e843 has been approved by oli-obk

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Oct 20, 2020
JohnTitor added a commit to JohnTitor/rust that referenced this pull request Oct 21, 2020
@JohnTitor
Rollup merge of rust-lang#78101 - RalfJung:foreign-static, r=oli-obk
dbb36ab 
fix static_ptr_ty for foreign statics

Cc rust-lang#74840

This does not fix that issue but fixes a problem in `static_ptr_ty` that we noticed while discussing that issue. I also added and updated a few comments. The one about `internal` locals being ignored does not seem to have been true [even in the commit that introduced it](https://github.com/rust-lang/rust/pull/44700/files#diff-ae2f3c7e2f9744f7ef43e96072b10e98d4e3fe74a3a399a3ad8a810fbe56c520R139).

r? @oli-obk
@JohnTitor JohnTitor mentioned this pull request Oct 21, 2020
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@JohnTitor JohnTitor mentioned this pull request Oct 21, 2020
Merged
bors added a commit to rust-lang-ci/rust that referenced this pull request Oct 21, 2020
@bors
Auto merge of rust-lang#78178 - JohnTitor:rollup-dslazzj, r=JohnTitor
1935645 
Rollup of 7 pull requests

Successful merges:

 - rust-lang#77726 (Add Pin::static_ref, static_mut.)
 - rust-lang#78002 (Tweak "object unsafe" errors)
 - rust-lang#78056 (BTreeMap: split off most code of remove and split_off)
 - rust-lang#78063 (Improve wording of "cannot multiply" type error)
 - rust-lang#78094 (rustdoc: Show the correct source filename in page titles, without `.html`)
 - rust-lang#78101 (fix static_ptr_ty for foreign statics)
 - rust-lang#78118 (Inline const followups)

Failed merges:

r? `@ghost`
@bors bors merged commit 83f126b into rust-lang:master Oct 21, 2020
@rustbot rustbot added this to the 1.49.0 milestone Oct 21, 2020
@RalfJung RalfJung deleted the foreign-static branch October 24, 2020 11:43
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