mpsc queue gives valgrind errors

[diwic]

When running the test suite for dbus-rs under valgrind, I get some errors that I don't think is my fault, because there is nothing in the backtrace indicating that would be the case.

Here's an example of that error:

Thread 1:
Conditional jump or move depends on uninitialised value(s)
    at 0x1E9030: sync::mpsc::Receiver$LT$T$GT$::recv::h14764315989133460255
    by 0x1D5D14: run_tests_console::hc794948cddbbd498cOb 
    by 0x1D2524: test_main::h01cefcc5e315671918a
    by 0x1D9CEA: test_main_static::h37e8bff01539d867Hbb
    by 0x1D0DB8: __test::main::hd07f3551eb4cd558Y2e
    by 0x240138: rust_try_inner
    by 0x240125: rust_try
    by 0x23D514: rt::lang_start::h8ce3e548818099f0bSL
    by 0x1D0F04: main
  Uninitialised value was created by a stack allocation
    at 0x1E8457: sync::mpsc::Receiver$LT$T$GT$::recv::h14764315989133460255

[diwic]

I tried to nail it but no luck so far. Here's the instruction where it breaks:

   0x00000000001e901e <+3070>:  callq  0x1eaff0 <_ZN4sync4mpsc6shared15Packet$LT$T$GT$8try_recv20h9233234408304405675E>
   0x00000000001e9023 <+3075>:  movzwl 0xde0(%rsp),%eax
   0x00000000001e902b <+3083>:  cmp    $0xff,%eax
=> 0x00000000001e9030 <+3088>:  ja     0x1e9392 <_ZN4sync4mpsc17Receiver$LT$T$GT$4recv21h14764315989133460255E+3954>
   0x00000000001e9036 <+3094>:  movzbl %al,%eax
   0x00000000001e9039 <+3097>:  cmp    $0x1,%eax
   0x00000000001e903c <+3100>:  jne    0x1e9392 <_ZN4sync4mpsc17Receiver$LT$T$GT$4recv21h14764315989133460255E+3954>
   0x00000000001e9042 <+3106>:  lea    0xde0(%rsp),%r12
   0x00000000001e904a <+3114>:  mov    %r12,%rdi
   0x00000000001e904d <+3117>:  callq  0x228790 <_ZN4sync4mpsc8blocking6tokens20hc880a4e85e4c780bbnyE>

And the matching Rust code would be, I believe, in sync/mpsc/shared.rs:

pub fn recv(&mut self) -> Result<T, Failure> {
    // This code is essentially the exact same as that found in the stream
    // case (see stream.rs)
    match self.try_recv() {
        Err(Empty) => {}
        data => return data,
    }

    let (wait_token, signal_token) = blocking::tokens();

...but I don't know enough about Rust's internals to know what the 0xff actually stands for here, that the uninitialised value is compared against?

[mahkoh]

Those errors come from cargo and not dbus-rs:

~/dragons$ cargo new hurrdurr
~/dragons$ cd hurrdurr 
~/dragons/hurrdurr$ valgrind cargo build
==8063== Memcheck, a memory error detector
==8063== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==8063== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==8063== Command: cargo build
==8063== 
==8063== Conditional jump or move depends on uninitialised value(s)
==8063==    at 0x3BBDBC: synonym::SynonymMap$LT$K$C$$u20$V$GT$::insert::h3724314155202151280 (in /usr/local/bin/cargo)
==8063==    by 0x3C1FAE: parse::PatParser$LT$$u27$a$GT$::add_atom_ifnotexists::h5c3eddacff495282Glc (in /usr/local/bin/cargo)
==8063==    by 0x3BD0D4: parse::PatParser$LT$$u27$a$GT$::pattern::hf8a955ff6e4a5adet2b (in /usr/local/bin/cargo)
==8063==    by 0x3C1ACE: parse::PatParser$LT$$u27$a$GT$::group::he9c6ce2fbc0887eaimc (in /usr/local/bin/cargo)
==8063==    by 0x3BE266: parse::PatParser$LT$$u27$a$GT$::pattern::hf8a955ff6e4a5adet2b (in /usr/local/bin/cargo)
==8063==    by 0x3B83BC: parse::PatParser$LT$$u27$a$GT$::parse::h90fccbc0b26f2df600b (in /usr/local/bin/cargo)
==8063==    by 0x3B2E7B: parse::Parser::new::h93460f743e7f69d7wsb (in /usr/local/bin/cargo)
==8063==    by 0x1729AC: Docopt::new::h4465346578811968731 (in /usr/local/bin/cargo)
==8063==    by 0x170C42: call_main_without_stdin::h6322948571204322835 (in /usr/local/bin/cargo)
==8063==    by 0x16F80C: main::h14917aa7cb75c12bwca (in /usr/local/bin/cargo)
==8063==    by 0x6A0C18: rust_try_inner (in /usr/local/bin/cargo)
==8063==    by 0x6A0C05: rust_try (in /usr/local/bin/cargo)
==8063== 
==8063== Conditional jump or move depends on uninitialised value(s)
==8063==    at 0x23B64C: ops::cargo_compile::compile_pkg::hbb6f4c5ae72d634apNh (in /usr/local/bin/cargo)
==8063==    by 0x23A827: ops::cargo_compile::compile::h459aef7669fb9faapIh (in /usr/local/bin/cargo)
==8063==    by 0x184512: call_main_without_stdin::h16575523244349200905 (in /usr/local/bin/cargo)
==8063==    by 0x175E15: execute::hecf542bd15794221Ica (in /usr/local/bin/cargo)
==8063==    by 0x171E08: call_main_without_stdin::h6322948571204322835 (in /usr/local/bin/cargo)
==8063==    by 0x16F80C: main::h14917aa7cb75c12bwca (in /usr/local/bin/cargo)
==8063==    by 0x6A0C18: rust_try_inner (in /usr/local/bin/cargo)
==8063==    by 0x6A0C05: rust_try (in /usr/local/bin/cargo)
==8063==    by 0x69DF0C: rt::lang_start::h61cf7984fd279964KzJ (in /usr/local/bin/cargo)
==8063==    by 0x54787FF: (below main) (in /usr/lib/libc-2.21.so)
==8063== 
==8063== Conditional jump or move depends on uninitialised value(s)
==8063==    at 0x2C85ED: sync::mpsc::Receiver$LT$T$GT$::recv::h13638071427880253445 (in /usr/local/bin/cargo)
==8063==    by 0x2467D9: ops::cargo_rustc::compile_targets::haf1e4fe4221dba30P9m (in /usr/local/bin/cargo)
==8063==    by 0x23F0E6: ops::cargo_compile::compile_pkg::hbb6f4c5ae72d634apNh (in /usr/local/bin/cargo)
==8063==    by 0x23A827: ops::cargo_compile::compile::h459aef7669fb9faapIh (in /usr/local/bin/cargo)
==8063==    by 0x184512: call_main_without_stdin::h16575523244349200905 (in /usr/local/bin/cargo)
==8063==    by 0x175E15: execute::hecf542bd15794221Ica (in /usr/local/bin/cargo)
==8063==    by 0x171E08: call_main_without_stdin::h6322948571204322835 (in /usr/local/bin/cargo)
==8063==    by 0x16F80C: main::h14917aa7cb75c12bwca (in /usr/local/bin/cargo)
==8063==    by 0x6A0C18: rust_try_inner (in /usr/local/bin/cargo)
==8063==    by 0x6A0C05: rust_try (in /usr/local/bin/cargo)
==8063==    by 0x69DF0C: rt::lang_start::h61cf7984fd279964KzJ (in /usr/local/bin/cargo)
==8063==    by 0x54787FF: (below main) (in /usr/lib/libc-2.21.so)
==8063== 
==8063== Conditional jump or move depends on uninitialised value(s)
==8063==    at 0x2C3233: ops::cargo_rustc::job_queue::JobQueue$LT$$u27$a$C$$u20$$u27$b$GT$::run::ha0306ea69322c899Fxm (in /usr/local/bin/cargo)
==8063==    by 0x2467AE: ops::cargo_rustc::compile_targets::haf1e4fe4221dba30P9m (in /usr/local/bin/cargo)
==8063==    by 0x23F0E6: ops::cargo_compile::compile_pkg::hbb6f4c5ae72d634apNh (in /usr/local/bin/cargo)
==8063==    by 0x23A827: ops::cargo_compile::compile::h459aef7669fb9faapIh (in /usr/local/bin/cargo)
==8063==    by 0x184512: call_main_without_stdin::h16575523244349200905 (in /usr/local/bin/cargo)
==8063==    by 0x175E15: execute::hecf542bd15794221Ica (in /usr/local/bin/cargo)
==8063==    by 0x171E08: call_main_without_stdin::h6322948571204322835 (in /usr/local/bin/cargo)
==8063==    by 0x16F80C: main::h14917aa7cb75c12bwca (in /usr/local/bin/cargo)
==8063==    by 0x6A0C18: rust_try_inner (in /usr/local/bin/cargo)
==8063==    by 0x6A0C05: rust_try (in /usr/local/bin/cargo)
==8063==    by 0x69DF0C: rt::lang_start::h61cf7984fd279964KzJ (in /usr/local/bin/cargo)
==8063==    by 0x54787FF: (below main) (in /usr/lib/libc-2.21.so)
==8063==

[mahkoh]

Well, that's not quite what I meant. The point is that those errors are also in cargo so dbus-rs is probably not the culprit. The error you posted above comes directly from the test framework initialization and not from a test.

[tamird]

Looks like #5856. @alexcrichton?

[alexcrichton]

Ah yes I believe so, thanks @tamird!