Promoteds can contain raw pointers, but these must still only point to immutable allocations #67603

oli-obk · 2019-12-25T13:02:14Z

cc @wesleywiser in order to not change behaviour in this PR, const prop uses the constant rules for interning, but at least there's an explicit mode for it now that we can think about this in the future

src/librustc_mir/interpret/intern.rs

bors · 2019-12-26T16:46:54Z

☔ The latest upstream changes (presumably #67327) made this pull request unmergeable. Please resolve the merge conflicts.

src/librustc_mir/interpret/intern.rs

SimonSapin · 2020-01-03T11:06:03Z

Friendly ping: what’s next for this PR? Can I help?

oli-obk · 2020-01-03T11:12:32Z

I just haven't gotten to it. Probably Tuesday or some other day next week

oli-obk · 2020-01-08T09:17:59Z

I addressed all review comments and marked the issue as a stable to nightly regression

RalfJung · 2020-01-09T09:10:23Z

src/librustc_mir/interpret/intern.rs

+                InternKind::Promoted => {
+                    alloc.mutability = Mutability::Not;
+                }
+                InternKind::Constant | InternKind::ConstProp => {


Right, I was thinking about this branch here when asking about nested allocations in constants. Isn't this unreachable then?

It is reachable, but I'm entirely unclean on why it is reachable

const RAW_TRAIT_OBJ_CONTENT_INVALID: *const dyn Trait = &unsafe { BoolTransmute { val: 3 }.bl } as *const _;

hits the InternKind::Constant arm.

See the MIR on https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=3bc6c8b165b614bbe6cf5566d30752de there's no StorageDead for the allocation containing the bool with bit pattern 3.

I'm not really sure what's going on there. Technically, since we're inside a constant, shouldn't this trigger promotion and promote the transmuted value?

Under unleash it's also reached in

const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;

but that triggers the delay_span_bug as expected.

Also under unleash, but without an ICE (just triggering the dynamic checks in interp):

const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _; //~^ WARN: skipping const checks const MUTATING_BEHIND_RAW: () = { // Test that `MUTABLE_BEHIND_RAW` is actually immutable, by doing this at const time. unsafe { *MUTABLE_BEHIND_RAW = 99 //~ ERROR any use of this value will cause an error } };

I'm not really sure what's going on there. Technically, since we're inside a constant, shouldn't this trigger promotion and promote the transmuted value?

Ah, this must be the "not-promotion" also described in this document (Ctrl-F "looks like"). That makes sense.

What I don't understand though is why RAW_TRAIT_OBJ_CONTENT_INVALID doesn't trigger the ICE. Why is the allocation already immutable?

(The PR doesn't change anything here so this doesn't block landing, but I'd really like to understand this and then see it documented.)

I would find documentation here immensely helpful.

If you have a holistic view of what happens, it would really help to write that down.

I don't, which is why my answers are so confusing. They are just a brain dump of me discovering what is going on, not me understanding it entirely

These issues are preexisting, so after this PR is merged I'll open a new one to write docs and actually figure out what is going on

I don't, which is why my answers are so confusing. They are just a brain dump of me discovering what is going on, not me understanding it entirely

Fair enough. :)

src/librustc_mir/interpret/intern.rs

bors · 2020-01-10T05:53:17Z

☔ The latest upstream changes (presumably #68078) made this pull request unmergeable. Please resolve the merge conflicts.

src/librustc_mir/interpret/intern.rs

bors · 2020-01-11T18:04:04Z

☔ The latest upstream changes (presumably #67000) made this pull request unmergeable. Please resolve the merge conflicts.

RalfJung · 2020-01-13T14:47:31Z

r=me with the if let Some(_) = ecx.tcx.alloc_map.lock().get(alloc_id) branch removed.

src/librustc_mir/interpret/intern.rs

…o immutable allocations

Co-Authored-By: Ralf Jung <post@ralfj.de>

oli-obk · 2020-01-15T10:50:18Z

@bors r=RalfJung

bors · 2020-01-15T10:50:20Z

📌 Commit 69ffe7b has been approved by RalfJung

RalfJung · 2020-01-15T11:05:34Z

@bors p=1 (regression fix, and this has been sitting for a while)

bors · 2020-01-15T16:28:12Z

⌛ Testing commit 69ffe7b with merge faf45c5...

@RalfJung

Promoteds can contain raw pointers, but these must still only point to immutable allocations fixes #67601 r? @RalfJung cc @wesleywiser in order to not change behaviour in this PR, const prop uses the constant rules for interning, but at least there's an explicit mode for it now that we can think about this in the future

bors · 2020-01-15T19:40:38Z

☀️ Test successful - checks-azure
Approved by: RalfJung
Pushing faf45c5 to master...

rust-highfive · 2020-01-15T19:41:47Z

📣 Toolstate changed by #67603!

Tested on commit faf45c5.
Direct link to PR: #67603

💔 rls on linux: test-pass → test-fail (cc @Xanewok, @rust-lang/infra).

@Xanewok

Tested on commit rust-lang/rust@faf45c5. Direct link to PR: <rust-lang/rust#67603> 💔 rls on linux: test-pass → test-fail (cc @Xanewok, @rust-lang/infra).

SimonSapin · 2020-01-15T20:49:37Z

Confirmed that this fixes #67601 for Servo. Thanks!

Upgrade to rustc 1.42.0-nightly (3291ae339 2020-01-15) This was unblocked by rust-lang/rust#67603 fixing rust-lang/rust#67601.

rust-highfive assigned RalfJung Dec 25, 2019

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Dec 25, 2019

RalfJung reviewed Dec 25, 2019

View reviewed changes

src/librustc_mir/interpret/intern.rs Outdated Show resolved Hide resolved

RalfJung reviewed Dec 25, 2019

View reviewed changes

src/librustc_mir/interpret/intern.rs Outdated Show resolved Hide resolved

RalfJung reviewed Dec 25, 2019

View reviewed changes

src/librustc_mir/interpret/intern.rs Outdated Show resolved Hide resolved

RalfJung reviewed Dec 26, 2019

View reviewed changes

src/librustc_mir/interpret/intern.rs Outdated Show resolved Hide resolved

RalfJung added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jan 2, 2020

oli-obk force-pushed the no_mut_static_ref_from_const branch from cc9326c to 1af201c Compare January 8, 2020 09:17

RalfJung reviewed Jan 9, 2020

View reviewed changes

src/librustc_mir/interpret/intern.rs Show resolved Hide resolved

RalfJung reviewed Jan 9, 2020

View reviewed changes

src/librustc_mir/interpret/intern.rs Show resolved Hide resolved

RalfJung reviewed Jan 9, 2020

View reviewed changes

src/librustc_mir/interpret/intern.rs Outdated Show resolved Hide resolved

RalfJung reviewed Jan 9, 2020

View reviewed changes

src/librustc_mir/interpret/intern.rs Outdated Show resolved Hide resolved

oli-obk force-pushed the no_mut_static_ref_from_const branch from 1af201c to 5053f1b Compare January 10, 2020 08:12

RalfJung reviewed Jan 10, 2020

View reviewed changes

src/librustc_mir/interpret/intern.rs Outdated Show resolved Hide resolved

RalfJung reviewed Jan 13, 2020

View reviewed changes

src/librustc_mir/interpret/intern.rs Outdated Show resolved Hide resolved

oli-obk and others added 6 commits January 15, 2020 10:48

Promoteds can contain raw pointers, but these must still only point t…

10f439a

…o immutable allocations

Elaborate on comments

658c27b

Elaborate on the details in some comments

1ea4466

Clean up comment

eadfd63

Update src/librustc_mir/interpret/intern.rs

b2c43dc

Co-Authored-By: Ralf Jung <post@ralfj.de>

Undo a change not neceesary for this bugfix

a81784a

oli-obk added 2 commits January 15, 2020 11:33

Typo

7bd01ed

Address review comments

69ffe7b

oli-obk force-pushed the no_mut_static_ref_from_const branch from e1479dd to 69ffe7b Compare January 15, 2020 10:50

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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jan 15, 2020

bors added the merged-by-bors This PR was explicitly merged by bors. label Jan 15, 2020

bors merged commit 69ffe7b into rust-lang:master Jan 15, 2020

SimonSapin mentioned this pull request Jan 16, 2020

Upgrade to rustc 1.42.0-nightly (3291ae339 2020-01-15) servo/servo#25536

Merged

bors-servo pushed a commit to servo/servo that referenced this pull request Jan 16, 2020

Auto merge of #25536 - servo:rustup, r=jdm

2293342

Upgrade to rustc 1.42.0-nightly (3291ae339 2020-01-15) This was unblocked by rust-lang/rust#67603 fixing rust-lang/rust#67601.

bors-servo pushed a commit to servo/servo that referenced this pull request Jan 16, 2020

Auto merge of #25536 - servo:rustup, r=jdm

dd5fdae

Upgrade to rustc 1.42.0-nightly (3291ae339 2020-01-15) This was unblocked by rust-lang/rust#67603 fixing rust-lang/rust#67601.

bors-servo pushed a commit to servo/servo that referenced this pull request Jan 16, 2020

Auto merge of #25536 - servo:rustup, r=jdm

7392d69

Upgrade to rustc 1.42.0-nightly (3291ae339 2020-01-15) This was unblocked by rust-lang/rust#67603 fixing rust-lang/rust#67601.

bors-servo pushed a commit to servo/servo that referenced this pull request Jan 16, 2020

Auto merge of #25536 - servo:rustup, r=jdm

3e44850

Upgrade to rustc 1.42.0-nightly (3291ae339 2020-01-15) This was unblocked by rust-lang/rust#67603 fixing rust-lang/rust#67601.

bors-servo pushed a commit to servo/servo that referenced this pull request Jan 16, 2020

Auto merge of #25536 - servo:rustup, r=jdm

0e9d89c

Upgrade to rustc 1.42.0-nightly (3291ae339 2020-01-15) This was unblocked by rust-lang/rust#67603 fixing rust-lang/rust#67601.

RalfJung mentioned this pull request Feb 13, 2020

update immutable-checking situation rust-lang/const-eval#36

Merged

pnkfelix mentioned this pull request Feb 20, 2020

internal compiler error: src/librustc_mir_build/hair/constant.rs:60: impossible case reached #69310

Closed

oli-obk deleted the no_mut_static_ref_from_const branch March 16, 2021 12:13

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Promoteds can contain raw pointers, but these must still only point to immutable allocations #67603

Promoteds can contain raw pointers, but these must still only point to immutable allocations #67603

oli-obk commented Dec 25, 2019

bors commented Dec 26, 2019

SimonSapin commented Jan 3, 2020

oli-obk commented Jan 3, 2020

oli-obk commented Jan 8, 2020

RalfJung Jan 9, 2020

oli-obk Jan 9, 2020

oli-obk Jan 9, 2020

RalfJung Jan 10, 2020

RalfJung Jan 10, 2020

RalfJung Jan 13, 2020

wesleywiser Jan 13, 2020

oli-obk Jan 15, 2020

oli-obk Jan 15, 2020

RalfJung Jan 15, 2020

bors commented Jan 10, 2020

bors commented Jan 11, 2020

RalfJung commented Jan 13, 2020

oli-obk commented Jan 15, 2020

bors commented Jan 15, 2020

RalfJung commented Jan 15, 2020

bors commented Jan 15, 2020

bors commented Jan 15, 2020

rust-highfive commented Jan 15, 2020

SimonSapin commented Jan 15, 2020

Promoteds can contain raw pointers, but these must still only point to immutable allocations #67603

Promoteds can contain raw pointers, but these must still only point to immutable allocations #67603

Conversation

oli-obk commented Dec 25, 2019

bors commented Dec 26, 2019

SimonSapin commented Jan 3, 2020

oli-obk commented Jan 3, 2020

oli-obk commented Jan 8, 2020

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

Choose a reason for hiding this comment

bors commented Jan 10, 2020

bors commented Jan 11, 2020

RalfJung commented Jan 13, 2020

oli-obk commented Jan 15, 2020

bors commented Jan 15, 2020

RalfJung commented Jan 15, 2020

bors commented Jan 15, 2020

bors commented Jan 15, 2020

rust-highfive commented Jan 15, 2020

SimonSapin commented Jan 15, 2020