`error: could not exec the linker 'emcc'` on windows while compiling some basic rust code

[akatechis]

Full error message:

$ rustc --target=wasm32-unknown-emscripten hello.rs
error: could not exec the linker `emcc`: The system cannot find the file specified. (os error 2)
  |
  = note: "emcc" "-L" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib" "hello.0.o" "-o" "hello.js" "-Wl,--gc-sections" "-nodefaultlibs" "-L" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib" "-Wl,-Bstatic" "-Wl,-Bdynamic" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libstd-17342542cc541012.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\librand-46ed9b788a6928f6.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libcollections-e32369d7fef31fbf.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\librustc_unicode-844a33a197b559a5.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libpanic_unwind-f78756b576499725.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libunwind-11f7709e0c71505b.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\liballoc-24699c1ddb055eb0.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\liballoc_system-3e467e865c8fa572.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\liblibc-60365c932e50e382.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libcore-d9873b515905cac5.rlib" "C:\\Users\\Alex\\.multirust\\toolchains\\nightly-x86_64-pc-windows-msvc\\lib\\rustlib\\wasm32-unknown-emscripten\\lib\\libcompiler_builtins-e428224f6caf212a.rlib" "-l" "c" "-s" "BINARYEN=1" "-s" "ERROR_ON_UNDEFINED_SYMBOLS=1"

I'm currently following the instructions at https://users.rust-lang.org/t/compiling-to-the-web-with-rust-and-emscripten/7627 to compile some rust code into wasm32.

I followed the instructions to install emscriptensdk from the website, and ran the following:

$ emsdk activate sdk-incoming-64bit
Writing .emscripten configuration file to user home directory C:\Users\Alex/
The Emscripten configuration file C:\Users\Alex\.emscripten has been rewritten with the following contents:

import os
LLVM_ROOT='C:/Program Files/Emscripten/clang/fastcomp/build_incoming_vs2013_64/RelWithDebInfo/bin'
NODE_JS='C:/Program Files/Emscripten/node/4.1.1_64bit/bin/node'
PYTHON='C:/Program Files/Emscripten/python/2.7.5.3_64bit/python.exe'
JAVA='C:/Program Files/Emscripten/java/7.45_64bit/bin/java.exe'
EMSCRIPTEN_ROOT='C:/Program Files/Emscripten/emscripten/incoming'
EMSCRIPTEN_NATIVE_OPTIMIZER='C:/Program Files/Emscripten/emscripten/incoming_64bit_optimizer/RelWithDebInfo/optimizer.exe'
SPIDERMONKEY_ENGINE = ''
V8_ENGINE = ''
TEMP_DIR = 'c:/users/alex/appdata/local/temp'
COMPILER_ENGINE = NODE_JS
JS_ENGINES = [NODE_JS]

Adding directories to PATH:
PATH += C:\Program Files\Emscripten\clang\fastcomp\build_incoming_vs2013_64\RelWithDebInfo\bin
PATH += C:\Program Files\Emscripten\node\4.1.1_64bit\bin
PATH += C:\Program Files\Emscripten\emscripten\incoming

Setting environment variables:
EM_CONFIG = C:\Users\Alex\.emscripten
JAVA_HOME = C:\Program Files\Emscripten\java\7.45_64bit
EMSCRIPTEN = C:\Program Files\Emscripten\emscripten\incoming

To permanently register this environment globally to all users in Windows Registry, rerun the command with the option --global.

I suspect that the issue is python, because when I just run emcc command, I get /usr/bin/env: ‘python2’: No such file or directory, but if I run which python I get /c/Python27/python.
I'm using Git Bash rather than CMD. Should I create a symlink to point python2 to python?

[kripken]

A symlink is one option, another is to set python2 in the settings file where it has PYTHON= there.

[juj]

Generally Git Bash and Cygwin are untested configurations, so rough edges are expected there.

You could try explicitly running emcc.bat instead of emcc, because that batch file is what gets invoked when running on a native Windows command prompt. Although I'm scratching my head a bit to try to understand why it is accessing python2 here even, since the shebang at https://github.com/kripken/emscripten/blob/incoming/emcc#L1 doesn't have python2 and I think this line shouldn't be hit either, because the earlier if sys.version_info.major == 2: should be true since you've got Python 2.7.

[cramertj]

I'm hitting the same issue, but mine seems unrelated to python:

λ rustc --target=asmjs-unknown-emscripten hello.rs | clip
error: could not exec the linker `emcc`: The system cannot find the file specified. (os error 2)
  |
  = note: "emcc" "-L" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib" "hello.0.o" "-o" "hello.js" "-Wl,--gc-sections" "-nodefaultlibs" "-L" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib" "-Wl,-Bstatic" "-Wl,-Bdynamic" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\libstd-17342542cc541012.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\librand-46ed9b788a6928f6.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\libpanic_unwind-f78756b576499725.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\libcollections-e32369d7fef31fbf.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\liballoc-24699c1ddb055eb0.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\liballoc_system-3e467e865c8fa572.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\libunwind-11f7709e0c71505b.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\liblibc-60365c932e50e382.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\librustc_unicode-844a33a197b559a5.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\libcore-d9873b515905cac5.rlib" "C:\\Users\\crame\\.rustup\\toolchains\\nightly-i686-pc-windows-gnu\\lib\\rustlib\\asmjs-unknown-emscripten\\lib\\libcompiler_builtins-e428224f6caf212a.rlib" "-l" "c" "-s" "ERROR_ON_UNDEFINED_SYMBOLS=1"

error: aborting due to previous error

Running emcc directly on the resulting .o files gives an error like the following:

C:/Program Files/Emscripten/clang/fastcomp/build_incoming_vs2015_64/RelWithDebInfo/bin\llvm-link: c:userscrameappdatalocaltemptmpprnv9pstrlwr.c.o: error: Could not open input file: no such file or directory
C:/Program Files/Emscripten/clang/fastcomp/build_incoming_vs2015_64/RelWithDebInfo/bin\llvm-link: error loading file 'c:userscrameappdatalocaltemptmpprnv9pstrlwr.c.o'
Traceback (most recent call last):
  File "C:\Program Files\Emscripten\emscripten\1.35.0\\emcc", line 1222, in <module>
    extra_files_to_link += system_libs.calculate([f for _, f in sorted(temp_files)] + extra_files_to_link, in_temp, stdout, stderr, forced=forced_stdlibs)
  File "C:\Program Files\Emscripten\emscripten\1.35.0\tools\system_libs.py", line 339, in calculate
    libfile = shared.Cache.get(name, do_create, extension=suffix)
  File "C:\Program Files\Emscripten\emscripten\1.35.0\tools\cache.py", line 41, in get
    temp = creator()
  File "C:\Program Files\Emscripten\emscripten\1.35.0\tools\system_libs.py", line 337, in do_create
    ret = create(name)
  File "C:\Program Files\Emscripten\emscripten\1.35.0\tools\system_libs.py", line 119, in create_libc
    return build_libc(libname, libc_files, args)
  File "C:\Program Files\Emscripten\emscripten\1.35.0\tools\system_libs.py", line 66, in build_libc
    shared.Building.link(o_s, in_temp(lib_filename))
  File "C:\Program Files\Emscripten\emscripten\1.35.0\tools\shared.py", line 1432, in link
    assert os.path.exists(target) and (output is None or 'Could not open input file' not in output), 'Linking error: ' + output
AssertionError: Linking error:

And no, there's nothing after "Linking error:" 😄

[juj]

I believe the issue is inside rustc, and it is attempting to invoke the executable emcc without enabling shell expansion. In that case, the compiler name should be specified as emcc.bat or ['python', 'emcc'] (The file emcc in the repository is a python file and not an executable file), or rustc be fixed to enable shell expansion on the subprocess it is spawning so that Windows properly expands it to rustc.bat.

Perhaps report this to Rust bug tracker?

[Lemures]

Has anyone found the solution to this problem?

[stale]

This issue has been automatically marked as stale because there has been no activity in the past year. It will be closed automatically if no further activity occurs in the next 7 days. Feel free to re-open at any time if this issue is still relevant.