Ensure that evaluating or validating a constant never reads from a static #67337

oli-obk · 2019-12-15T20:54:00Z

This does not yet address the fact that evaluation of a constant can read from a static (under unleash-miri)

oli-obk · 2019-12-16T12:51:24Z

Oh I just realized this PR makes no sense. If the user points into the static, this PR won't detect that. We could poison Allocations in statics by adding a new flag to them... Or we scrap this approach entirely and just check accesses to statics during interpretation.

RalfJung · 2019-12-16T13:28:14Z

Oh I just realized this PR makes no sense. If the user points into the static, this PR won't detect that. We could poison Allocations in statics by adding a new flag to them... Or we scrap this approach entirely and just check accesses to statics during interpretation.

So if I recall correctly, in rust-lang/const-eval#17 (comment) and https://github.com/rust-lang/const-eval/blob/master/const.md#reading-statics, I also came to the conclusion that we want to guard accesses during execution, and not the final value.

RalfJung · 2019-12-18T13:48:44Z

as per #66302 (comment)

That comment talks about not reading from (mutable) statics. I don't understand the connection to the final value not containing certain relocations.

Oh I just realized this PR makes no sense. If the user points into the static, this PR won't detect that.

Also, isn't code like this allowed?

static FOO: i32 = 13;
const FOOPTR: &i32 = &FOO;

So, I don't entirely understand how we even could backwards-compatibly forbid consts pointing to statics, and why we would want that?

src/librustc_mir/const_eval.rs

oli-obk · 2019-12-18T13:57:20Z

Also, isn't code like this allowed?

No:

error[E0013]: constants cannot refer to statics, use a constant instead
 --> src/lib.rs:2:22
  |
2 | const FOOPTR: &i32 = &FOO;
  |                      ^^^^

oli-obk · 2019-12-18T14:00:25Z

That comment talks about not reading from (mutable) statics. I don't understand the connection to the final value not containing certain relocations.

Hmm... I guess I went overboard when looking at it from the perspective of the comment, but just referencing a static is not allowed on stable, so this is what we want to forbid right now.

bors · 2019-12-21T17:37:24Z

☔ The latest upstream changes (presumably #67485) made this pull request unmergeable. Please resolve the merge conflicts.

src/librustc_mir/interpret/intern.rs

src/test/ui/consts/const-points-to-static.rs

RalfJung · 2019-12-22T18:14:49Z

Hmm... I guess I went overboard when looking at it from the perspective of the comment, but just referencing a static is not allowed on stable, so this is what we want to forbid right now.

Well, what this PR implement is not accessing a static. So the PR description is wrong, IMO.

Except that, somehow, this also excludes referencing a static, and I am not sure why.

src/librustc_mir/interpret/intern.rs

src/test/ui/consts/miri_unleashed/const_refers_to_static.rs

bors · 2019-12-23T05:52:46Z

☔ The latest upstream changes (presumably #67540) made this pull request unmergeable. Please resolve the merge conflicts.

src/librustc_mir/const_eval.rs

src/librustc_mir/interpret/intern.rs

and some uses of it will be illegal forever (e.g. mutable or interior mutable statics)

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

rust-highfive · 2019-12-23T15:55:55Z

The job x86_64-gnu-llvm-7 of your PR failed (pretty log, raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

2019-12-23T14:48:40.5384394Z ##[command]git remote add origin https://github.com/rust-lang/rust
2019-12-23T14:48:40.5579767Z ##[command]git config gc.auto 0
2019-12-23T14:48:40.5656063Z ##[command]git config --get-all http.https://github.com/rust-lang/rust.extraheader
2019-12-23T14:48:40.5700120Z ##[command]git config --get-all http.proxy
2019-12-23T14:48:40.5845230Z ##[command]git -c http.extraheader="AUTHORIZATION: basic ***" fetch --force --tags --prune --progress --no-recurse-submodules --depth=2 origin +refs/heads/*:refs/remotes/origin/* +refs/pull/67337/merge:refs/remotes/pull/67337/merge
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---
2019-12-23T15:55:36.1797116Z 
2019-12-23T15:55:36.1797713Z ---- [ui] ui/consts/miri_unleashed/mutable_const2.rs stdout ----
2019-12-23T15:55:36.1797780Z diff of stderr:
2019-12-23T15:55:36.1797818Z 
2019-12-23T15:55:36.1798077Z 10 LL | const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
2019-12-23T15:55:36.1798283Z 12 
2019-12-23T15:55:36.1798283Z 12 
2019-12-23T15:55:36.1798689Z - thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:347:17
2019-12-23T15:55:36.1799143Z + thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:349:17
2019-12-23T15:55:36.1800187Z 15 
2019-12-23T15:55:36.1800245Z 16 error: internal compiler error: unexpected panic
2019-12-23T15:55:36.1800302Z 
2019-12-23T15:55:36.1800615Z 
2019-12-23T15:55:36.1800615Z 
2019-12-23T15:55:36.1800687Z The actual stderr differed from the expected stderr.
2019-12-23T15:55:36.1801166Z Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/miri_unleashed/mutable_const2/mutable_const2.stderr
2019-12-23T15:55:36.1801893Z To update references, rerun the tests and pass the `--bless` flag
2019-12-23T15:55:36.1802418Z To only update this specific test, also pass `--test-args consts/miri_unleashed/mutable_const2.rs`
2019-12-23T15:55:36.1802763Z error: 1 errors occurred comparing output.
2019-12-23T15:55:36.1802814Z status: exit code: 101
2019-12-23T15:55:36.1802814Z status: exit code: 101
2019-12-23T15:55:36.1803865Z command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/consts/miri_unleashed/mutable_const2.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/miri_unleashed/mutable_const2" "-Crpath" "-O" "-Cdebuginfo=0" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-Zunleash-the-miri-inside-of-you" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/miri_unleashed/mutable_const2/auxiliary" "-A" "unused"
2019-12-23T15:55:36.1804487Z ------------------------------------------
2019-12-23T15:55:36.1804527Z 
2019-12-23T15:55:36.1804970Z ------------------------------------------
2019-12-23T15:55:36.1805169Z stderr:
2019-12-23T15:55:36.1805169Z stderr:
2019-12-23T15:55:36.1805484Z ------------------------------------------
2019-12-23T15:55:36.1805683Z warning: skipping const checks
2019-12-23T15:55:36.1806035Z   --> /checkout/src/test/ui/consts/miri_unleashed/mutable_const2.rs:15:38
2019-12-23T15:55:36.1806219Z    |
2019-12-23T15:55:36.1806326Z LL | const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
2019-12-23T15:55:36.1806450Z 
2019-12-23T15:55:36.1806514Z error: internal compiler error: mutable allocation in constant
2019-12-23T15:55:36.1806952Z   --> /checkout/src/test/ui/consts/miri_unleashed/mutable_const2.rs:15:1
2019-12-23T15:55:36.1807157Z    |
2019-12-23T15:55:36.1807157Z    |
2019-12-23T15:55:36.1807262Z LL | const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
2019-12-23T15:55:36.1807382Z 
2019-12-23T15:55:36.1807382Z 
2019-12-23T15:55:36.1807786Z thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:349:17
2019-12-23T15:55:36.1808068Z 
2019-12-23T15:55:36.1808118Z error: internal compiler error: unexpected panic
2019-12-23T15:55:36.1808175Z 
2019-12-23T15:55:36.1808264Z note: the compiler unexpectedly panicked. this is a bug.
2019-12-23T15:55:36.1808264Z note: the compiler unexpectedly panicked. this is a bug.
2019-12-23T15:55:36.1808316Z 
2019-12-23T15:55:36.1808820Z note: we would appreciate a bug report: ***/blob/master/CONTRIBUTING.md#bug-reports
2019-12-23T15:55:36.1808861Z 
2019-12-23T15:55:36.1809658Z note: rustc 1.42.0-nightly (4ded390fd 2019-12-23) running on x86_64-unknown-linux-gnu
2019-12-23T15:55:36.1809897Z 
2019-12-23T15:55:36.1810392Z note: compiler flags: -Z threads=1 -Z ui-testing -Z unstable-options -Z unleash-the-miri-inside-of-you -C prefer-dynamic -C rpath -C debuginfo=0
2019-12-23T15:55:36.1810633Z 
2019-12-23T15:55:36.1810981Z ------------------------------------------
2019-12-23T15:55:36.1811144Z 
2019-12-23T15:55:36.1811226Z 
---
2019-12-23T15:55:36.1830883Z thread 'main' panicked at 'Some tests failed', src/tools/compiletest/src/main.rs:385:22
2019-12-23T15:55:36.1830990Z note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
2019-12-23T15:55:36.1847631Z 
2019-12-23T15:55:36.1848404Z 
2019-12-23T15:55:36.1850819Z command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-7/bin/FileCheck" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0 -Zunstable-options  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python2.7" "--lldb-python" "/usr/bin/python2.7" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "7.0.0\n" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
2019-12-23T15:55:36.1851387Z 
2019-12-23T15:55:36.1851441Z 
2019-12-23T15:55:36.1865193Z failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
2019-12-23T15:55:36.1865299Z Build completed unsuccessfully in 1:00:48
2019-12-23T15:55:36.1865299Z Build completed unsuccessfully in 1:00:48
2019-12-23T15:55:36.1921339Z == clock drift check ==
2019-12-23T15:55:36.1940165Z   local time: Mon Dec 23 15:55:36 UTC 2019
2019-12-23T15:55:36.4766259Z   network time: Mon, 23 Dec 2019 15:55:36 GMT
2019-12-23T15:55:36.4771871Z == end clock drift check ==
2019-12-23T15:55:37.4116269Z 
2019-12-23T15:55:37.4201711Z ##[error]Bash exited with code '1'.
2019-12-23T15:55:37.4246723Z ##[section]Starting: Checkout
2019-12-23T15:55:37.4248486Z ==============================================================================
2019-12-23T15:55:37.4248544Z Task         : Get sources
2019-12-23T15:55:37.4248592Z Description  : Get sources from a repository. Supports Git, TfsVC, and SVN repositories.

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

RalfJung · 2019-12-23T16:38:11Z

Looking good! r=me with tests blessed.

oli-obk · 2019-12-23T16:48:41Z

@bors r=RalfJung

bors · 2019-12-23T16:48:43Z

📌 Commit 87fea04 has been approved by RalfJung

bors · 2019-12-23T16:48:44Z

🌲 The tree is currently closed for pull requests below priority 100, this pull request will be tested once the tree is reopened

@RalfJung

…t, r=RalfJung Ensure that evaluating or validating a constant never reads from a static r? @RalfJung as per rust-lang#66302 (comment) This does not yet address the fact that evaluation of a constant can read from a static (under unleash-miri)

@ghost

Rollup of 7 pull requests Successful merges: - #67337 (Ensure that evaluating or validating a constant never reads from a static) - #67543 (Add regression tests for fixed ICEs) - #67547 (Cleanup err codes) - #67551 (Add long error code explanation message for E0627) - #67561 (remove `description` from `Error` impls in docs) - #67569 (Clean up unsafety in char::encode_utf8) - #67572 (Use the chocolatey CDN directly to avoid the flaky API) Failed merges: r? @ghost

rust-highfive assigned RalfJung Dec 15, 2019

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oli-obk force-pushed the no_mut_static_ref_from_const branch from 0f986ca to c0faa51 Compare December 16, 2019 14:23

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oli-obk force-pushed the no_mut_static_ref_from_const branch from c0faa51 to fc0c48c Compare December 22, 2019 20:43

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oli-obk changed the title ~~Ensure that a constant's final value never contains a relocation into a static~~ Ensure that evaluating or validating a constant never reads from a static Dec 23, 2019

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oli-obk and others added 5 commits December 23, 2019 14:54

Panic on mutable allocs in constants

640e288

Dynamically prevent constants from accessing statics

ad6b9c7

Constants reading or referencing statics is illegal

2022fac

and some uses of it will be illegal forever (e.g. mutable or interior mutable statics)

Show const_err lints

e56a861

Update src/librustc_mir/interpret/intern.rs

89250b9

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

oli-obk force-pushed the no_mut_static_ref_from_const branch from 3168051 to 89250b9 Compare December 23, 2019 13:55

Tidy

75bdd95

Bless tests

87fea04

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 Dec 23, 2019

Mark-Simulacrum mentioned this pull request Dec 24, 2019

Rollup of 7 pull requests #67573

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Centril mentioned this pull request Dec 24, 2019

Rollup of 7 pull requests #67575

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bors merged commit 87fea04 into rust-lang:master Dec 24, 2019

RalfJung mentioned this pull request Dec 24, 2019

Dynamic checks for all const soundness concerns? rust-lang/const-eval#17

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SimonSapin mentioned this pull request Dec 25, 2019

Regression in Servo: "internal compiler error: mutable allocation in constant" #67601

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Ensure that evaluating or validating a constant never reads from a static #67337

Ensure that evaluating or validating a constant never reads from a static #67337

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Ensure that evaluating or validating a constant never reads from a static #67337

Ensure that evaluating or validating a constant never reads from a static #67337

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