Nightly Rust hangs forever with a simple 2-line dotenv_codegen and println!

[brainstorm]

The offending code is just a dotenv macro inside a println! macro:

fn main() {
    println!("{}", dotenv!("AWS_ATHENA_DB").to_string());
    println!(dotenv!("AWS_ATHENA_DB").to_string());
}

Just clone the following repository and run cargo build:

https://github.com/brainstorm/dotenv-codegen-rustc-hang

Stays on Building forever:

$ cargo build --verbose
       Fresh unicode-xid v0.1.0
       Fresh cc v1.0.37
       Fresh rustc-demangle v0.1.15
       Fresh lazy_static v1.3.0
       Fresh ucd-util v0.1.3
       Fresh cfg-if v0.1.9
       Fresh utf8-ranges v1.0.3
       Fresh proc-macro2 v0.4.30
       Fresh thread_local v0.3.6
       Fresh regex-syntax v0.6.7
       Fresh quote v0.6.12
       Fresh libc v0.2.58
       Fresh memchr v2.2.0
       Fresh syn v0.15.38
       Fresh backtrace-sys v0.1.29
       Fresh aho-corasick v0.7.3
       Fresh synstructure v0.10.2
       Fresh backtrace v0.3.32
       Fresh regex v1.1.7
       Fresh proc-macro-hack v0.5.7
       Fresh failure_derive v0.1.5
       Fresh failure v0.1.5
       Fresh dotenv v0.14.1
       Fresh dotenv_codegen_implementation v0.14.1
       Fresh dotenv_codegen v0.14.1
   Compiling dotenv-codegen-rustc-hang v0.1.0 (/home/limsadmin/.rvalls/dotenv-codegen-rustc-hang)
     Running `rustc --edition=2018 --crate-name dotenv_codegen_rustc_hang src/main.rs --color always --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=8547a0ee33801234 -C extra-filename=-8547a0ee33801234 --out-dir /home/limsadmin/.rvalls/dotenv-codegen-rustc-hang/target/debug/deps -C incremental=/home/limsadmin/.rvalls/dotenv-codegen-rustc-hang/target/debug/incremental -L dependency=/home/limsadmin/.rvalls/dotenv-codegen-rustc-hang/target/debug/deps --extern dotenv_codegen=/home/limsadmin/.rvalls/dotenv-codegen-rustc-hang/target/debug/deps/libdotenv_codegen-f886d4c0e76d6020.rlib`
    Building [======================================================>  ] 39/40: dotenv-codegen-rustc-hang(bin)

Meta

rustc 1.37.0-nightly (d3e2cec29 2019-06-26)
binary: rustc
commit-hash: d3e2cec29225a46298ec4ebf082f34ebd7cfeecf
commit-date: 2019-06-26
host: x86_64-unknown-linux-gnu
release: 1.37.0-nightly
LLVM version: 8.0

[oli-obk]

unnominating, I'm guessing it's a dotenv problem and not a rustc problem. The compilation probably hangs forever because the dotenv proc macro blocks or goes into an infinite loop

[jonas-schievink]

What's AWS_ATHENA_DB set to when building?

[lukaslueg]

librustc_driver hangs while joining on a thread stuck as

#0  0x00007f373032266a in scoped_tls::ScopedKey<T>::with () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libsyntax_pos-2ce5298cca1cb4db.so
#1  0x00007f37303270ef in syntax_pos::<impl syntax_pos::span_encoding::Span>::macro_backtrace () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libsyntax_pos-2ce5298cca1cb4db.so
#2  0x00007f373055da78 in rustc_errors::emitter::EmitterWriter::fix_multispan_in_std_macros () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_errors-9de40152414e6deb.so
#3  0x00007f373055a33a in <rustc_errors::emitter::EmitterWriter as rustc_errors::emitter::Emitter>::emit_diagnostic () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_errors-9de40152414e6deb.so
#4  0x00007f3730573897 in rustc_errors::Handler::emit_db () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_errors-9de40152414e6deb.so
#5  0x00007f3730556d88 in rustc_errors::diagnostic_builder::DiagnosticBuilder::emit () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_errors-9de40152414e6deb.so
#6  0x00007f372d64d7e5 in syntax_ext::format::expand_preparsed_format_args () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/../lib/libsyntax_ext-d81e66d3e7998764.so
#7  0x00007f372d64a4b9 in <F as syntax::ext::base::TTMacroExpander>::expand () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/../lib/libsyntax_ext-d81e66d3e7998764.so
#8  0x00007f3730b89892 in syntax::ext::expand::MacroExpander::expand_invoc () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libsyntax-301f938611d84d7d.so
#9  0x00007f3730b8407b in syntax::ext::expand::MacroExpander::expand_fragment () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libsyntax-301f938611d84d7d.so
#10 0x00007f3730b8326d in syntax::ext::expand::MacroExpander::expand_crate () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/libsyntax-301f938611d84d7d.so
#11 0x00007f373358140b in rustc_interface::passes::configure_and_expand_inner::{{closure}} () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_interface-a6451c13da8356b3.so
#12 0x00007f373357877f in rustc::util::common::time () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_interface-a6451c13da8356b3.so
#13 0x00007f373352410d in rustc_interface::passes::configure_and_expand_inner () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_interface-a6451c13da8356b3.so
#14 0x00007f37335808ef in rustc_interface::passes::configure_and_expand::{{closure}} () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_interface-a6451c13da8356b3.so
#15 0x00007f3733550842 in rustc_data_structures::box_region::PinnedGenerator<I,A,R>::new () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_interface-a6451c13da8356b3.so
#16 0x00007f3733521276 in rustc_interface::passes::configure_and_expand () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_interface-a6451c13da8356b3.so
#17 0x00007f3733511d5e in rustc_interface::queries::Query<T>::compute () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_interface-a6451c13da8356b3.so
#18 0x00007f37335125bd in rustc_interface::queries::Query<T>::compute () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_interface-a6451c13da8356b3.so
#19 0x00007f37335115a6 in rustc_interface::queries::Query<T>::compute () from /home/lukas/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin/../lib/../lib/librustc_interface-a6451c13da8356b3.so

[brainstorm]

@jonas-schievink The AWS_ATHENA_DB is just "foo", from .env file:

https://github.com/brainstorm/dotenv-codegen-rustc-hang/blob/master/.env

[brainstorm]

@oli-obk After poking around it for a few minutes, it seems like https://github.com/dtolnay/proc-macro-hack, a dotenv dependency, is the culprit instead of dotenv-rs/dotenv#22... but in any case, shouldn't rustc's macro processor (plugin?) be more resilient and timeout/fail or handle this more gracefully instead of hanging forever?