Adding nom as a dependency to a proc-macro crate with tests results in link error

[killercup]

Long debug session short:

• Having a proc-macro crate with tests works.
• Adding nom 5 as a dependency to a proc-macro crate works.
• Having nom 5 be a dependency in a proc-macro crate with tests does not work.

This might be a known problem; I couldn't find an open issue, though. Even so, error is not user friendly and that should at least be fixed.

cargo test --verbose

       Fresh semver-parser v0.7.0
       Fresh void v1.0.2
       Fresh version_check v0.1.5
       Fresh static_assertions v0.2.5
       Fresh cfg-if v0.1.9
       Fresh semver v0.9.0
       Fresh rustc_version v0.2.3
       Fresh unreachable v1.0.0
       Fresh ryu v0.2.8
       Fresh memchr v2.2.0
       Fresh stackvector v1.0.6
       Fresh lexical-core v0.4.2
       Fresh nom v5.0.0
   Compiling le-proc-macro v0.1.0 (/Users/pascal/Projekte/rust-proc-macro-test-linking-error/le-proc-macro)
     Running `rustc --edition=2018 --crate-name le_proc_macro le-proc-macro/src/lib.rs --color always --crate-type proc-macro --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 -C metadata=88a723aab0e69935 -C extra-filename=-88a723aab0e69935 --out-dir /Users/pascal/.cargo/global-target/debug/deps -C incremental=/Users/pascal/.cargo/global-target/debug/incremental -L dependency=/Users/pascal/.cargo/global-target/debug/deps --extern nom=/Users/pascal/.cargo/global-target/debug/deps/libnom-1f917ff11a098652.rlib -Zsymbol-mangling-version=v0`
     Running `rustc --edition=2018 --crate-name le_proc_macro le-proc-macro/src/lib.rs --color always --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 --test -C metadata=a6088ffbe5f8f402 -C extra-filename=-a6088ffbe5f8f402 --out-dir /Users/pascal/.cargo/global-target/debug/deps -C incremental=/Users/pascal/.cargo/global-target/debug/incremental -L dependency=/Users/pascal/.cargo/global-target/debug/deps --extern nom=/Users/pascal/.cargo/global-target/debug/deps/libnom-1f917ff11a098652.rlib -Zsymbol-mangling-version=v0`
warning: unused import: `nom::IResult`
 --> le-proc-macro/src/lib.rs:4:5
  |
4 | use nom::IResult;
  |     ^^^^^^^^^^^^
  |
  = note: #[warn(unused_imports)] on by default

warning: unused import: `nom::IResult`
 --> le-proc-macro/src/lib.rs:4:5
  |
4 | use nom::IResult;
  |     ^^^^^^^^^^^^
  |
  = note: #[warn(unused_imports)] on by default

error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-m64" "-L" "/Users/pascal/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402.15tcejuoevmooxrp.rcgu.o" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402.2t5ie6p57602b1hc.rcgu.o" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402.3k5tdhzyfh385jbb.rcgu.o" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402.40gtnqu5cs3dsn54.rcgu.o" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402.4qorxw028kxfrme3.rcgu.o" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402.52k0bg5o47l9e5g5.rcgu.o" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402.al00ie0yzyrbvcs.rcgu.o" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402.mt4xvaos1670dho.rcgu.o" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402.uo2b4vausxznfy0.rcgu.o" "-o" "/Users/pascal/.cargo/global-target/debug/deps/le_proc_macro-a6088ffbe5f8f402" "-Wl,-dead_strip" "-nodefaultlibs" "-L" "/Users/pascal/.cargo/global-target/debug/deps" "-L" "/Users/pascal/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib" "-L" "/Users/pascal/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib" "-ltest-0d2e540bfeb389c9" "-L" "/Users/pascal/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib" "-lterm-9dc2d4db7993fbfd" "/Users/pascal/.cargo/global-target/debug/deps/libnom-1f917ff11a098652.rlib" "-L" "/Users/pascal/.cargo/global-target/debug/deps" "-llexical_core-d715db2534c4793d" "/Users/pascal/.cargo/global-target/debug/deps/libryu-aa307abc73a251bb.rlib" "/Users/pascal/.cargo/global-target/debug/deps/libstackvector-8faea803e8d71d93.rlib" "/Users/pascal/.cargo/global-target/debug/deps/libunreachable-5224a131bd9f1445.rlib" "/Users/pascal/.cargo/global-target/debug/deps/libvoid-196f5b851425c571.rlib" "/Users/pascal/.cargo/global-target/debug/deps/libstatic_assertions-633d173cf8830653.rlib" "/Users/pascal/.cargo/global-target/debug/deps/libcfg_if-3eb3c0e2c877bcb6.rlib" "/Users/pascal/.cargo/global-target/debug/deps/libmemchr-affb19acc32f58a0.rlib" "/Users/pascal/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib/libproc_macro-027ee96af4731d93.rlib" "-L" "/Users/pascal/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib" "-lstd-a62aa059e97bb248" "/Users/pascal/.rustup/toolchains/nightly-x86_64-apple-darwin/lib/rustlib/x86_64-apple-darwin/lib/libcompiler_builtins-a62aa322f1655fc7.rlib" "-lSystem" "-lresolv" "-lc" "-lm"
  = note: Undefined symbols for architecture x86_64:
            "__RNvXsJ_NtCs6GOKu7pHlyt_4core3fmtRlNtB5_5Debug3fmtCs7N6e5JiROWN_12lexical_core", referenced from:
                __RINvCsLl3UznTzjj_4test18assert_test_resultuECsfbY9ZosDsBF_13le_proc_macro in le_proc_macro-a6088ffbe5f8f402.al00ie0yzyrbvcs.rcgu.o
          ld: symbol(s) not found for architecture x86_64
          clang: error: linker command failed with exit code 1 (use -v to see invocation)
          

error: aborting due to previous error

error: Could not compile `le-proc-macro`.

Caused by:
  process didn't exit successfully: `rustc --edition=2018 --crate-name le_proc_macro le-proc-macro/src/lib.rs --color always --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 --test -C metadata=a6088ffbe5f8f402 -C extra-filename=-a6088ffbe5f8f402 --out-dir /Users/pascal/.cargo/global-target/debug/deps -C incremental=/Users/pascal/.cargo/global-target/debug/incremental -L dependency=/Users/pascal/.cargo/global-target/debug/deps --extern nom=/Users/pascal/.cargo/global-target/debug/deps/libnom-1f917ff11a098652.rlib -Zsymbol-mangling-version=v0` (exit code: 1)
warning: build failed, waiting for other jobs to finish...
error: build failed

See these commits for a minimal repo: https://github.com/killercup/rust-proc-macro-test-linking-error/commits/master

Tested with rustc 1.37.0-nightly (7840a0b75 2019-05-31) and rustc 1.35.0 (3c235d560 2019-05-20).

cc @fry because we originally encountered this issue in https://github.com/fry/memory-offset-match

cc @Geal because he might have done something horrible in nom 5 or one of its dependencies :)

[CAD97]

Interestingly, tests on the bad commit pass on windows-gnu and fails to link on windows-msvc.

windows-msvc

   Compiling le-proc-macro v0.1.0 (D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\le-proc-macro)
     Running `rustc --edition=2018 --crate-name le_proc_macro le-proc-macro\src\lib.rs --color never --crate-type proc-macro --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 -C metadata=79c80939141ae4ac -C extra-filename=-79c80939141ae4ac --out-dir D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps -C incremental=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\incremental -L dependency=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps --extern nom=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps\libnom-c94b7c84eb2825cd.rlib`
     Running `rustc --edition=2018 --crate-name le_proc_macro le-proc-macro\src\lib.rs --color never --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 --test -C metadata=7bd3bb9f841cfff7 -C extra-filename=-7bd3bb9f841cfff7 --out-dir D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps -C incremental=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\incremental -L dependency=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps --extern nom=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps\libnom-c94b7c84eb2825cd.rlib`

error: linking with `link.exe` failed: exit code: 1120
  |
  = note: "C:\\Program Files (x86)\\Microsoft Visual Studio\\2017\\Community\\VC\\Tools\\MSVC\\14.16.27023\\bin\\HostX64\\x64\\link.exe" "/NOLOGO" "/NXCOMPAT" "/LIBPATH:D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.1g0nlq9cs4pghkmy.rcgu.o" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.2zq0lgz10lh544dg.rcgu.o" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.3vphv4whkenx5uyc.rcgu.o" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.423daslz1834a6cl.rcgu.o" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.4f1glrg3bse6z664.rcgu.o" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.4wjf5uz2ryqnq3zw.rcgu.o" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.5dntnuq9q5dsobng.rcgu.o" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.5vrr76dttgz35ko.rcgu.o" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.eiqbwkic980ji4a.rcgu.o" "/OUT:D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\le_proc_macro-7bd3bb9f841cfff7.exe" "/OPT:REF,NOICF" "/DEBUG" "/NATVIS:D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\etc\\intrinsic.natvis" "/NATVIS:D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\etc\\liballoc.natvis" "/NATVIS:D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\etc\\libcore.natvis" "/LIBPATH:D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps" "/LIBPATH:D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "/LIBPATH:D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "test-a4f6d8bebcc4a634.dll.lib" "/LIBPATH:D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "term-b5d0d8083a2dc6b6.dll.lib" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\libnom-c94b7c84eb2825cd.rlib" "/LIBPATH:D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps" "lexical_core-7f0416c2f53c1ea3.dll.lib" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\libryu-180662a1e54e289b.rlib" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\libstackvector-397c1e3495a8af16.rlib" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\libunreachable-0de66d9fa8096f40.rlib" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\libvoid-bd42d54b51e6fb3b.rlib" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\libstatic_assertions-e1a33ab607fbc814.rlib" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\libcfg_if-0effb27d46321e26.rlib" "D:\\usr\\Documents\\Code\\Rust\\rust-proc-macro-test-linking-error\\target\\debug\\deps\\libmemchr-764cfb4774939518.rlib" "D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libproc_macro-4d1f432750330cc0.rlib" "/LIBPATH:D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib" "std-f293fd7c6c200025.dll.lib" "D:\\usr\\.rustup\\toolchains\\beta-x86_64-pc-windows-msvc\\lib\\rustlib\\x86_64-pc-windows-msvc\\lib\\libcompiler_builtins-6e806524bc879616.rlib" "kernel32.lib" "advapi32.lib" "ws2_32.lib" "userenv.lib" "msvcrt.lib"
  = note: le_proc_macro-7bd3bb9f841cfff7.5dntnuq9q5dsobng.rcgu.o : error LNK2019: unresolved external symbol _ZN42_$LT$$RF$T$u20$as$u20$core..fmt..Debug$GT$3fmt17h2afd837e3afa95dfE referenced in function _ZN4test18assert_test_result17h4c0919ab0062322cE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.15.rcgu.o) : error LNK2019: unresolved external symbol _ZN44_$LT$$RF$T$u20$as$u20$core..fmt..Display$GT$3fmt17hf14e8c15e740b9fbE referenced in function _ZN44_$LT$$RF$T$u20$as$u20$core..fmt..Display$GT$3fmt17haab549e68c83ac1dE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.15.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core3fmt10ArgumentV13new17hc9a2b5195c3df041E referenced in function _ZN4core6result13unwrap_failed17h04085d1dcae3d677E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.3.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core3mem7size_of17h92a2f9b2285fe98bE referenced in function _ZN5alloc7raw_vec11alloc_guard17hbd50e116f525187dE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.6.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core3cmp3Ord3max17h23fc9564fa9d697fE referenced in function _ZN4core3cmp3max17hd0540b0469402e52E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.6.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core3ptr4null17hcd56d8e489039dbcE referenced in function _ZN4core3ptr33_$LT$impl$u20$$BP$const$u20$T$GT$7is_null17h8e5689cafc2eeb2bE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.0.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core3ptr4null17hcd56d8e489039dbcE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.6.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core3ptr33_$LT$impl$u20$$BP$const$u20$T$GT$12wrapping_add17h73cb510101ad8f41E referenced in function _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$4iter17h558ad527c14070e5E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.0.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core3ptr33_$LT$impl$u20$$BP$const$u20$T$GT$12wrapping_add17h73cb510101ad8f41E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.6.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$8is_empty17h292f2354d65f1217E referenced in function _ZN6memchr6memchr17h096a2154009159f5E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.4.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$8is_empty17h292f2354d65f1217E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.13.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$8is_empty17h292f2354d65f1217E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.4.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$10as_mut_ptr17h74c681e1ce352f74E referenced in function _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$15copy_from_slice17h7425f79218280e4bE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.5.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$10as_mut_ptr17h74c681e1ce352f74E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.4.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$4iter17h5de8a72d254d3c81E referenced in function _ZN4core5slice87_$LT$impl$u20$core..iter..traits..collect..IntoIterator$u20$for$u20$$RF$$u5b$T$u5d$$GT$9into_iter17hd669a6aba8572ef2E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.5.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$4iter17h5de8a72d254d3c81E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.7.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$4iter17h5de8a72d254d3c81E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.1.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$4iter17h5de8a72d254d3c81E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.4.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core3ptr33_$LT$impl$u20$$BP$const$u20$T$GT$15wrapping_offset17hb99f1d9c96b35408E referenced in function _ZN85_$LT$core..slice..Iter$LT$T$GT$$u20$as$u20$core..iter..traits..iterator..Iterator$GT$4next17h393cb63c7e21b432E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.9.rcgu.o) : error LNK2019: unresolved external symbol _ZN99_$LT$core..ops..range..Range$LT$usize$GT$$u20$as$u20$core..slice..SliceIndex$LT$$u5b$T$u5d$$GT$$GT$17get_unchecked_mut17h647d054b48c4ddd1E referenced in function _ZN101_$LT$core..ops..range..RangeTo$LT$usize$GT$$u20$as$u20$core..slice..SliceIndex$LT$$u5b$T$u5d$$GT$$GT$17get_unchecked_mut17h28223c993ae50ebcE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.5.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core5slice18from_raw_parts_mut17h98d385ee41841199E referenced in function _ZN71_$LT$alloc..vec..Vec$LT$T$GT$$u20$as$u20$core..ops..deref..DerefMut$GT$9deref_mut17h4f0a111c1e19aaffE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.5.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core5slice74_$LT$impl$u20$core..ops..index..Index$LT$I$GT$$u20$for$u20$$u5b$T$u5d$$GT$5index17hb99a524821c5f831E referenced in function _ZN77_$LT$alloc..vec..Vec$LT$T$GT$$u20$as$u20$core..ops..index..Index$LT$I$GT$$GT$5index17hf110361d6411889cE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.1.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core5slice74_$LT$impl$u20$core..ops..index..Index$LT$I$GT$$u20$for$u20$$u5b$T$u5d$$GT$5index17hb99a524821c5f831E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.7.rcgu.o) : error LNK2019: unresolved external symbol _ZN85_$LT$core..slice..Iter$LT$T$GT$$u20$as$u20$core..iter..traits..iterator..Iterator$GT$4next17he6af94f7b2c0b0d1E referenced in function _ZN4core3str15next_code_point17hef324823ad4c0872E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.1.rcgu.o) : error LNK2001: unresolved external symbol _ZN85_$LT$core..slice..Iter$LT$T$GT$$u20$as$u20$core..iter..traits..iterator..Iterator$GT$4next17he6af94f7b2c0b0d1E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.7.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$3get17hf115a764b37e96b7E referenced in function _ZN4core3str21_$LT$impl$u20$str$GT$16is_char_boundary17h3c5e7a7aa3d1f0c6E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.2.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core5slice29_$LT$impl$u20$$u5b$T$u5d$$GT$3get17hf115a764b37e96b7E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.2.rcgu.o) : error LNK2019: unresolved external symbol _ZN63_$LT$I$u20$as$u20$core..iter..traits..collect..IntoIterator$GT$9into_iter17hf1888569ab79dc27E referenced in function _ZN4core3str7pattern14TwoWaySearcher4next17h4f9555b17b537e73E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.2.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core4iter5range101_$LT$impl$u20$core..iter..traits..iterator..Iterator$u20$for$u20$core..ops..range..Range$LT$A$GT$$GT$4next17ha062de3a3a9e0250E referenced in function _ZN4core3str7pattern14TwoWaySearcher4next17h4f9555b17b537e73E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.2.rcgu.o) : error LNK2019: unresolved external symbol _ZN4core3cmp5impls69_$LT$impl$u20$core..cmp..PartialEq$LT$$RF$B$GT$$u20$for$u20$$RF$A$GT$2eq17h311a204d80df372fE referenced in function _ZN81_$LT$core..str..pattern..CharSearcher$u20$as$u20$core..str..pattern..Searcher$GT$10next_match17hb6708e15064c8ea1E
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.1.rcgu.o) : error LNK2001: unresolved external symbol _ZN4core3cmp5impls69_$LT$impl$u20$core..cmp..PartialEq$LT$$RF$B$GT$$u20$for$u20$$RF$A$GT$2eq17h311a204d80df372fE
          libnom-c94b7c84eb2825cd.rlib(nom-c94b7c84eb2825cd.nom.89kj9cb1-cgu.1.rcgu.o) : error LNK2019: unresolved external symbol _ZN63_$LT$I$u20$as$u20$core..iter..traits..collect..IntoIterator$GT$9into_iter17h1823be92c3d60beaE referenced in function _ZN71_$LT$$RF$$u5b$u8$u5d$$u20$as$u20$nom..traits..FindToken$LT$char$GT$$GT$10find_token17h1563db97eca1d634E
          D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps\le_proc_macro-7bd3bb9f841cfff7.exe : fatal error LNK1120: 20 unresolved externals

windows-gnu

   Compiling le-proc-macro v0.1.0 (D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\le-proc-macro)
     Running `rustc --edition=2018 --crate-name le_proc_macro le-proc-macro\src\lib.rs --color never --crate-type proc-macro --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 -C metadata=c8b668c11ecd6d48 -C extra-filename=-c8b668c11ecd6d48 --out-dir D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps -C incremental=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\incremental -L dependency=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps --extern nom=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps\libnom-b1d68ca366aff2cb.rlib`
     Running `rustc --edition=2018 --crate-name le_proc_macro le-proc-macro\src\lib.rs --color never --emit=dep-info,link -C prefer-dynamic -C debuginfo=2 --test -C metadata=017bf7764872f271 -C extra-filename=-017bf7764872f271 --out-dir D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps -C incremental=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\incremental -L dependency=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps --extern nom=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps\libnom-b1d68ca366aff2cb.rlib`
   Compiling le-lib-crate v0.1.0 (D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\le-main-crate)
     Running `rustc --edition=2018 --crate-name le_lib_crate le-main-crate\src\main.rs --color never --emit=dep-info,link -C debuginfo=2 --test -C metadata=c57f79d95dd04475 -C extra-filename=-c57f79d95dd04475 --out-dir D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps -C incremental=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\incremental -L dependency=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps --extern le_proc_macro=D:\usr\Documents\Code\Rust\rust-proc-macro-test-linking-error\target\debug\deps\le_proc_macro-c8b668c11ecd6d48.dll`
    Finished dev [unoptimized + debuginfo] target(s) in 2.22s

[fwalch]

Encountered this today with Rust 1.36.0 on x86_64-unknown-linux-gnu when trying to upgrade a crate from Nom 4 to Nom 5.

I ran git bisect, which identified rust-bakery/nom@40f20aa as the first bad commit. The commit adds lexical-core as a new optional dependency behind the lexical feature, which is on by default.

Some observations:

• Changing default = ["std", "lexical"] to default = ["std"] in Nom's Cargo.toml fixes the linking error.
• Adding the Nom dependency with nom = { version = "5.0", features = ["std"] } in the proc-macro crate does not fix the linking error (am I doing this correctly?) Edit: I forgot to also specify default-features = false.
• Adding a dependency to just lexical-core (instead of Nom 5) in the proc-macro crate does not trigger the linking error

So I went one step further and had a look at lexical-core (Alexhuszagh/rust-lexical@078fff3). Observations from modifying lexical-core and using this modified version in Nom's Cargo.toml:

• Removing "correct" from lexical-core default features in its Cargo.toml fixes the proc-macro crate linking errors.
• lexical-core specifies crate-type = ["lib", "staticlib", "cdylib"] in its Cargo.toml. Removing cdylib from this also fixes the proc-macro crate linking errors.

[Geal]

@Alexhuszagh any idea about this?

[Alexhuszagh]

Thanks @fwalch and @Geal, removing correct from lexical-core may not be ideal, since that would invoke the lossy parser, which is a fast but lossy floating-point parser. Let me check if I can actually find the issues with this.

As far as "cdylib", my crate exports functions for C-FFI, but this can be easily removed and would just require users to designate the crate-type when building. Let me quickly check this on my end and try to ensure this is all working well.

[Alexhuszagh]

Ok, I'm going to move the C-API to an external crate, which will solve half of this issue. I'll try debugging for the proc-macro issues with different features enabled, thanks for the heads up.

[nikomatsakis]

Visiting from compiler triage meeting. I cannot tell if this is a compiler bug. It sounds vaguely like one -- including cdylib doesn't seem like it should on its own cause a link error? But I'm not sure, perhaps there is a legit error that only comes up when doing a cdylib build? Not sure how to categorize this, so leaving as is for this week.

[Alexhuszagh]

@nikomatsakis I've decided that it's likely best to separate the the C-API from the core crate, so this shouldn't be an issue. I'm more concerned about the correct feature not working, but I'll get there shortly.

[nikomatsakis]

@Alexhuszagh does that mean we should close this issue? I can also mark it as "P-medium" and people can re-nominate if/when it should be reconsidered.