vec_deque::tests::test_drain panicking on debug build

[pnkfelix]

vec_deque::tests::test_drain panicking on debug build

Here are my configure switches:

CFG_CONFIGURE_ARGS   := --enable-debug --enable-optimize --enable-ccache --prefix=~/opt/rust-dbg --disable-optimize-tests --disable-llvm-assertions

I suspect the important bit there is the --enable-debug.

When I run make check, it fails during collectionstest:

failures:                                                                                                         

---- vec_deque::tests::test_drain stdout ----                                                                     
        thread 'vec_deque::tests::test_drain' panicked at 'dst=0 src=7 len=2 cap=8', /home/fklock/Dev/Mozilla/rust.git/src/libcollections/vec_deque.rs:178                                                                         


failures:
    vec_deque::tests::test_drain

test result: FAILED. 18 passed; 1 failed; 0 ignored; 0 measured

I'm not familiar with the code in question, so its not immediately apparent if this is just a case of an invalid assertion, or some deeper violation of a structural invariant.

[Gankra]

cc @mystor

[mystor]

I'll try to look at this tonight. Not sure why that would be happening :-/

[apasel422]

Was this fixed by #29545?

[mystor]

yes, I believe it was.

[bluss]

How can it have escaped the buildbots in the first place?

[mystor]

@bluss I guess tests are not run in debug mode, so debug assertions aren't hit? Who knows.

[bluss]

That sounds terrifying

[apasel422]

@bluss The debug buildbot doesn't run tests. CC #27010.

[alexcrichton]

Yeah currently the builder that builds the standard library in debug mode is too slow to also run tests unfortunately :(

[Gankra]

One of many reasons why debug asserts are unfortunately borderline useless in std. :(

At least it was the test that was broken, and not the code!