Emscripten tries to write to /nix

busti · September 28, 2021, 9:36pm

I would like to use a nix shell environment to compile a project that needs emscripten. I have added the emscripten package to it.
I am trying to execute em++ but it fails to build a cache in the /nix directory.
Read-only file system: '/nix/store/<hash>-emscripten-2.0.27/share/emscripten/cache/ports

Is this a bug in the package itself? I guess it should be build in a way that would make it write that cache somewhere else.
Or am I doing something wrong?

busti · September 30, 2021, 2:20am

It seems like it is intended behavior of the package itself, especially when it is being used in building other packages. However the current behavior does not work for interactive shell usage.
See the attached issue for more info and a workaround for development usage:

github.com/NixOS/nixpkgs

Emscripten tries to write to /nix/store

opened 05:13PM - 29 Sep 21 UTC

closed 05:49PM - 22 May 22 UTC

busti

0.kind: bug

### Describe the bug I am trying to compile a project which (among other things…) uses emscripten. I have created a custom `shell.nix` file to create a development environment for the project. Executing the makefile fails when it gets to compiling the emscripten part of the project with the following error message: `OSError: [Errno 30] Read-only file system: '/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/cache/ports'` ### Steps To Reproduce The project makes use of the open source project imgui. One of it's examples can be used to reproduce the error message. 1. `git clone https://github.com/ocornut/imgui.git` 2. `cd examples/example_emscripten_opengl3` 3. create a file named `shell.nix` with the following contents: ```shell.nix {pkgs ? import <nixpkgs> {}}: pkgs.mkShell { nativeBuildInputs = with pkgs; [ gnumake gcc ]; buildInputs = with pkgs; [ emscripten ]; } ``` 4. run `nix-shell` 5. run `make` ### Expected behavior The command succeeds resulting in a compiled executable of the example project. ### Real behavior The execution of `make` fails with the following error: ``` $ make em++ -DIMGUI_DISABLE_FILE_FUNCTIONS -I../.. -I../../backends -Wall -Wformat -Os -s USE_SDL=2 -s DISABLE_EXCEPTION_CATCHING=1 -c -o main.o main.cpp Traceback (most recent call last): File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/em++.py", line 14, in <module> sys.exit(emcc.run(sys.argv)) File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/emcc.py", line 1074, in run linker_inputs = phase_compile_inputs(options, state, newargs, input_files) File "/nix/store/dqxic3j7csd4ywn94n4smmnz55p039g3-python3-3.9.6/lib/python3.9/contextlib.py", line 79, in inner return func(*args, **kwds) File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/emcc.py", line 2436, in phase_compile_inputs compile_source_file(i, input_file) File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/emcc.py", line 2416, in compile_source_file cmd = get_clang_command(input_file) File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/emcc.py", line 2357, in get_clang_command return get_compiler(use_cxx(src_file)) + get_cflags(options, state.orig_args) + compile_args + [src_file] File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/emcc.py", line 879, in get_cflags system_libs.add_ports_cflags(cflags, settings) File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/tools/system_libs.py", line 1969, in add_ports_cflags port.get(Ports, settings, shared) File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/tools/ports/sdl2.py", line 23, in get ports.fetch_project('sdl2', 'https://github.com/emscripten-ports/SDL2/archive/' + TAG + '.zip', SUBDIR, sha512hash=HASH) File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/tools/system_libs.py", line 1765, in fetch_project fullname = os.path.join(Ports.get_dir(), name) File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/tools/system_libs.py", line 1746, in get_dir shared.safe_ensure_dirs(dirname) File "/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/tools/utils.py", line 27, in safe_ensure_dirs os.makedirs(dirname, exist_ok=True) File "/nix/store/dqxic3j7csd4ywn94n4smmnz55p039g3-python3-3.9.6/lib/python3.9/os.py", line 225, in makedirs mkdir(name, mode) OSError: [Errno 30] Read-only file system: '/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/cache/ports' make: *** [Makefile:70: main.o] Error 1 ``` During building of the example project make tries to execute the command: `em++ -DIMGUI_DISABLE_FILE_FUNCTIONS -I../.. -I../../backends -Wall -Wformat -Os -s USE_SDL=2 -s DISABLE_EXCEPTION_CATCHING=1 -c -o main.o main.cpp` which fails with the error: `OSError: [Errno 30] Read-only file system: '/nix/store/ajv94air67dbyjramrjlv0y6j969hsyx-emscripten-2.0.27/share/emscripten/cache/ports'` ### Notify maintainers @qknight @matthewbauer ### Metadata - system: `"x86_64-linux"` - host os: `Linux 5.13.4, NixOS, 21.11 (Porcupine)` - multi-user?: `yes` - sandbox: `yes` - version: `nix-env (Nix) 2.3.15` - channels(root): `"nixos-21.11pre318500.51bcdc4cdaa"` - channels(mbust): `""` - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

karexix · October 23, 2023, 9:02am

Thank you, I was also trying to use emscripten from the command line nix-shell -p emscripten

I got the same error OSError: [Errno 30] Read-only file system: for the emscripten cache
your quick fix still works for emscripten 3.1.45