Check array indices in constant propagation #51308

fanzier · 2018-06-02T17:56:03Z

Previously, uses of constant weren't correctly propagated.
This fixes #48920.

r? @oli-obk because you suggested it

rust-highfive · 2018-06-02T18:10:43Z

The job x86_64-gnu-llvm-3.9 of your PR failed on Travis (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.


[00:05:08] travis_fold:start:tidy
travis_time:start:tidy
tidy check
[00:05:09] tidy error: /checkout/src/test/ui/const-eval/index_out_of_bounds.rs: missing trailing newline
[00:05:09] tidy error: /checkout/src/librustc_mir/transform/const_prop.rs:244: line longer than 100 chars
[00:05:09] tidy error: /checkout/src/librustc_mir/transform/const_prop.rs:249: line longer than 100 chars
[00:05:09] tidy error: /checkout/src/librustc_mir/transform/const_prop.rs:253: line longer than 100 chars
[00:05:09] tidy error: /checkout/src/librustc_mir/transform/const_prop.rs:274: line longer than 100 chars
[00:05:09] tidy error: /checkout/src/librustc_mir/transform/const_prop.rs:549: line longer than 100 chars
[00:05:10] some tidy checks failed
[00:05:10] 
[00:05:10] 
[00:05:10] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/tidy" "/checkout/src" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "--no-vendor" "--quiet"
[00:05:10] 
[00:05:10] 
[00:05:10] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test src/tools/tidy
[00:05:10] Build completed unsuccessfully in 0:01:52
[00:05:10] Build completed unsuccessfully in 0:01:52
[00:05:10] Makefile:79: recipe for target 'tidy' failed
[00:05:10] make: *** [tidy] Error 1

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:0113d94a
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

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)

oli-obk

My initial hope was that just propagating the Rvalue::Len would automatically cause the index out of bounds terminator to report its error.

Did you try to go down that route?

fanzier · 2018-06-03T18:04:52Z

Not sure what you mean with Rvalue::Len because I don't think this is emitted for arrays (just for slices). In this example, there is only a comparison of two constants (the array size and the index) and an assertion that this comparison is as expected:

    bb5: {                              
        StorageDead(_4);                 // bb5[0]: scope 0 at src/main.rs:2:37: 2:38
        StorageLive(_6);                 // bb5[1]: scope 1 at src/main.rs:3:5: 3:9
        StorageLive(_7);                 // bb5[2]: scope 1 at src/main.rs:3:7: 3:8
        _7 = const 1usize;               // bb5[3]: scope 1 at src/main.rs:3:7: 3:8
                                         // ty::Const
                                         // + ty: usize
                                         // + val: Value(Scalar(Bits { defined: 64, bits: 1 }))
                                         // mir::Constant
                                         // + span: src/main.rs:3:7: 3:8
                                         // + ty: usize
                                         // + literal: const 1usize
        _8 = const 1usize;               // bb5[4]: scope 1 at src/main.rs:3:5: 3:9
                                         // ty::Const
                                         // + ty: usize
                                         // + val: Value(Scalar(Bits { defined: 64, bits: 1 }))
                                         // mir::Constant
                                         // + span: src/main.rs:3:5: 3:9
                                         // + ty: usize
                                         // + literal: const 1usize
        _9 = Lt(_7, _8);                 // bb5[5]: scope 1 at src/main.rs:3:5: 3:9
        assert(move _9, "index out of bounds: the len is move _8 but the index is _7") -> bb6; // bb5[6]: scope 1 at src/main.rs:3:5: 3:9
    }

So I'll just look into what exactly has to be propagated here and adjust the PR. I think I understand what kind of approach you're thinking of.

oli-obk · 2018-06-03T18:21:35Z

So I'll just look into what exactly has to be propagated here and adjust the PR. I think I understand what kind of approach you're thinking of.

oh... that makes a lot of sense. So we're just failing badly at propagating those constants?

fanzier · 2018-06-03T18:55:38Z

Yes, exactly, this code in const_prop.rs was the problem:

            // No need to overwrite an already evaluated constant
            Rvalue::Use(Operand::Constant(box Constant {
                literal: Literal::Value {
                    value: &ty::Const {
                        val: ConstVal::Value(_),
                        ..
                    },
                },
                ..
            })) => None,

Removing this makes array index checks work. I'll do slices in a separate PR. Will update the commit in a minute.

rust-highfive · 2018-06-03T20:06:10Z

The job x86_64-gnu-llvm-3.9 of your PR failed on Travis (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.

[00:45:13] ...........................................................................i........................
[00:45:18] ....................................................................................................
[00:45:23] ....................................................................................................
[00:45:29] ....................................................................................................
[00:45:34] ........i.................iiiiiiiii...................................................
[00:45:34] 
[00:45:34] travis_fold:start:test_ui_nll
travis_time:start:test_ui_nll
Check compiletest suite=ui mode=ui compare_mode=nll (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
---
[00:46:23] ...........................................................................i........................
[00:46:28] ....................................................................................................
[00:46:32] ....................................................................................................
[00:46:38] ....................................................................................................
[00:46:42] ........i.................iiiiiiiii...................................................
[00:46:42] 
[00:46:42]  finished in 68.693
[00:46:42] travis_fold:end:test_ui_nll

---
[00:55:53] ....................................................................................................
[00:55:58] ....................................................................................................
[00:56:03] ....................................................................................................
[00:56:08] ....................................................................................................
[00:56:15] .......................................................F...FF.........................i.............
[00:56:26] ..............................................................................i.....................
[00:56:31] .......................i............................................................................
[00:56:35] ..............................................................................................i.....
[00:56:40] ....................................................................................................
---
[00:58:03] failures:
[00:58:03] 
[00:58:03] ---- [compile-fail] compile-fail/const-err-early.rs stdout ----
[00:58:03] 
[00:58:03] error: /checkout/src/test/compile-fail/const-err-early.rs:22: unexpected error: '22:1: 22:28: this constant cannot be used [const_err]'
[00:58:03] 
[00:58:03] error: 1 unexpected errors found, 0 expected errors not found
[00:58:03] status: exit code: 101
[00:58:03] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/compile-fail/const-err-early.rs" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail/const-err-early/a" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail/const-err-early/auxiliary" "-A" "unused"
[00:58:03] unexpected errors (from JSON output): [
[00:58:03]     Error {
[00:58:03]         line_num: 22,
[00:58:03]         kind: Some(
[00:58:03]         ),
[00:58:03]         ),
[00:58:03]         msg: "22:1: 22:28: this constant cannot be used [const_err]"
[00:58:03] ]
[00:58:03] 
[00:58:03] thread '[compile-fail] compile-fail/const-err-early.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:1284:13
[00:58:03] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[00:58:03] note: Run with `RUST_BACKTRACE=1` for a backtrace.
[00:58:03] 
[00:58:03] ---- [compile-fail] compile-fail/const-err3.rs stdout ----
[00:58:03] 
[00:58:03] error: /checkout/src/test/compile-fail/const-err3.rs:25: unexpected error: '25:14: 25:22: index out of bounds: the len is 1 but the index is 1 [const_err]'
[00:58:03] 
[00:58:03] error: 1 unexpected errors found, 0 expected errors not found
[00:58:03] status: exit code: 101
[00:58:03] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/compile-fail/const-err3.rs" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail/const-err3/a" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail/const-err3/auxiliary" "-A" "unused"
[00:58:03] unexpected errors (from JSON output): [
[00:58:03]     Error {
[00:58:03]         line_num: 25,
[00:58:03]         kind: Some(
[00:58:03]         ),
[00:58:03]         ),
[00:58:03]         msg: "25:14: 25:22: index out of bounds: the len is 1 but the index is 1 [const_err]"
[00:58:03] ]
[00:58:03] 
[00:58:03] thread '[compile-fail] compile-fail/const-err3.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:1284:13
[00:58:03] 
[00:58:03] 
[00:58:03] ---- [compile-fail] compile-fail/const-err2.rs stdout ----
[00:58:03] 
[00:58:03] error: /checkout/src/test/compile-fail/const-err2.rs:33: unexpected error: '33:14: 33:22: index out of bounds: the len is 1 but the index is 1 [const_err]'
[00:58:03] 
[00:58:03] error: 1 unexpected errors found, 0 expected errors not found
[00:58:03] status: exit code: 101
[00:58:03] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/compile-fail/const-err2.rs" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "-Zui-testing" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail/const-err2/a" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-O" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail/const-err2/auxiliary" "-A" "unused"
[00:58:03] unexpected errors (from JSON output): [
[00:58:03]     Error {
[00:58:03]         line_num: 33,
[00:58:03]         kind: Some(
[00:58:03]         ),
[00:58:03]         ),
[00:58:03]         msg: "33:14: 33:22: index out of bounds: the len is 1 but the index is 1 [const_err]"
[00:58:03] ]
[00:58:03] 
[00:58:03] thread '[compile-fail] compile-fail/const-err2.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:1284:13
[00:58:03] 
---
[00:58:03] 
[00:58:03] thread 'main' panicked at 'Some tests failed', tools/compiletest/src/main.rs:498:22
[00:58:03] 
[00:58:03] 
[00:58:03] command did not execute successfully: "/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/compile-fail" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/compile-fail" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--mode" "compile-fail" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-3.9/bin/FileCheck" "--host-rustcflags" "-Crpath -O -Zunstable-options " "--target-rustcflags" "-Crpath -O -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" "3.9.1\n" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--llvm-components" "" "--llvm-cxxflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--color" "always"
[00:58:03] 
[00:58:03] 
[00:58:03] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[00:58:03] Build completed unsuccessfully in 0:15:00
[00:58:03] Build completed unsuccessfully in 0:15:00
[00:58:03] Makefile:58: recipe for target 'check' failed
[00:58:03] make: *** [check] Error 1

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:03f3ee51
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)

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)

rust-highfive · 2018-06-03T22:46:27Z

The job x86_64-gnu-llvm-3.9 of your PR failed on Travis (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.

[00:48:51] ...........................................................................i........................
[00:48:56] ....................................................................................................
[00:49:02] ....................................................................................................
[00:49:08] ....................................................................................................
[00:49:13] ........i.................iiiiiiiii...................................................
[00:49:13] 
[00:49:13] travis_fold:start:test_ui_nll
travis_time:start:test_ui_nll
Check compiletest suite=ui mode=ui compare_mode=nll (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
---
[00:50:06] ...........................................................................i........................
[00:50:11] ....................................................................................................
[00:50:16] ....................................................................................................
[00:50:22] ....................................................................................................
[00:50:26] ........i.................iiiiiiiii...................................................
[00:50:26] 
[00:50:26]  finished in 73.493
[00:50:26] travis_fold:end:test_ui_nll

---
travis_time:start:test_run-fail
Check compiletest suite=run-fail mode=run-fail (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
[01:02:27] 
[01:02:27] running 142 tests
[01:02:38] .........................................................................FF.F.......................
[01:02:43]    |
[01:02:43] 16 |     C[10]
[01:02:43]    |     ^^^^^
[01:02:43]    |
[01:02:43]    |
[01:02:43]    = note: #[deny(const_err)] on by default
[01:02:43] error: aborting due to previous error
[01:02:43] 
[01:02:43] 
[01:02:43] ------------------------------------------
[01:02:43] ------------------------------------------
[01:02:43] 
[01:02:43] thread '[run-fail] run-fail/mir_indexing_oob_1.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:3096:9
[01:02:43] 
[01:02:43] ---- [run-fail] run-fail/mir_indexing_oob_2.rs stdout ----
[01:02:43] 
[01:02:43] error: compilation failed!
[01:02:43] status: exit code: 101
[01:02:43] command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/run-fail/mir_indexing_oob_2.rs" "--target=x86_64-unknown-linux-gnu" "-C" "prefer-dynamic" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/run-fail/mir_indexing_oob_2/a" "-Crpath" "-O" "-Zunstable-options" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/run-fail/mir_indexing_oob_2/auxiliary"
[01:02:43] ------------------------------------------
[01:02:43] 
[01:02:43] ------------------------------------------
[01:02:43] stderr:
[01:02:43] stderr:
[01:02:43] ------------------------------------------
[01:02:43] error: index out of bounds: the len is 5 but the index is 10
[01:02:43]   --> /checkout/src/test/run-fail/mir_indexing_oob_2.rs:16:5
[01:02:43] 16 |     C[10]
[01:02:43]    |     ^^^^^
[01:02:43]    |
[01:02:43]    |
[01:02:43]    = note: #[deny(const_err)] on by default
[01:02:43] error: abor04 ./obj/build/x86_64-unknown-linux-gnu/test/run-pass
34588 ./obj/build/x86_64-unknown-linux-gnu/native/jemalloc/lib
34372 ./obj/build/x86_64-unknown-linux-gnu/doc/core/arch
33884 ./src/llvm-emscripten/lib/Target

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)

oli-obk · 2018-06-04T08:32:43Z

You should #![allow(const_err)] in the failing run-fail tests, because while we know at compile-time that they are going to fail, the tests are supposed to test that the panic actually occurs

fanzier · 2018-06-04T14:10:02Z

Thanks, Travis is passing now

oli-obk · 2018-06-04T14:19:18Z

@bors r+

Awesome! Thanks

bors · 2018-06-04T14:19:20Z

📌 Commit 4db265b has been approved by oli-obk

bors · 2018-06-05T01:46:45Z

🔒 Merge conflict

fanzier · 2018-06-05T12:17:45Z

Rebased but didn't find any conflicts (?)

oli-obk · 2018-06-05T12:21:18Z

yea bors is a little confused lately

@bors r+

bors · 2018-06-05T12:21:18Z

📌 Commit 9600489 has been approved by oli-obk

@oli-obk

…ck, r=oli-obk Check array indices in constant propagation Previously, uses of constant weren't correctly propagated. This fixes rust-lang#48920. r? @oli-obk because you suggested it

Rollup of 7 pull requests Successful merges: - #50852 (Add doc comment to hiding portions of code example) - #51183 (Update rustdoc book to suggest using Termination trait instead of hidden ‘foo’ function) - #51255 (Fix confusing error message for sub_instant) - #51256 (Fix crate-name option in rustdoc) - #51308 (Check array indices in constant propagation) - #51343 (test: Ignore some problematic tests on sparc and sparc64) - #51358 (Tests that #39963 is fixed on MIR borrowck) Failed merges:

leonardo-m · 2018-06-09T06:42:35Z

Is code like this supposed to give an error in the last Nightly?

fn main() {
    let a: [i32; 1] = [0; 1];
    a[1];
}

oli-obk · 2018-06-09T23:22:30Z

It's just a lint and not an error, but yes indeed it should

leonardo-m · 2018-06-10T07:10:36Z

If I compile with "rustc test.rs" I see:

error: index out of bounds: the len is 1 but the index is 1
 --> test.rs:3:5
  |
3 |     a[1];
  |     ^^^^
  |
  = note: #[deny(const_err)] on by default

If I compile with "rustc --emit=metadata test.rs", I see no errors. Is this good?

oli-obk · 2018-06-10T13:43:59Z

Ugh.... that is weird. Open an issue?

leonardo-m · 2018-06-11T09:42:14Z

Opened as #51491

rust-highfive assigned oli-obk Jun 2, 2018

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 2, 2018

oli-obk reviewed Jun 2, 2018

View reviewed changes

fanzier force-pushed the const-prop-array-bounds-check branch from f34283a to 42bd288 Compare June 3, 2018 19:01

fanzier force-pushed the const-prop-array-bounds-check branch from c4fb5d7 to 4db265b Compare June 4, 2018 12:06

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 Jun 4, 2018

bors 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-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jun 5, 2018

fanzier added 3 commits June 5, 2018 10:35

Propagate uses of constants correctly so that array index checks work

589f9a8

Fix tidy

29c43fe

Fix tests

9600489

fanzier force-pushed the const-prop-array-bounds-check branch from 4db265b to 9600489 Compare June 5, 2018 12:16

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 Jun 5, 2018

Mark-Simulacrum mentioned this pull request Jun 5, 2018

Rollup of 7 pull requests #51369

Merged

bors merged commit 9600489 into rust-lang:master Jun 5, 2018

leonardo-m mentioned this pull request Jun 11, 2018

Unchecked array indices with --emit=metadata #51491

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Check array indices in constant propagation #51308

Check array indices in constant propagation #51308

fanzier commented Jun 2, 2018 •

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Check array indices in constant propagation #51308

Check array indices in constant propagation #51308

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