WasmFS NodeRawFS is not consistent with NodeRawFS (non-WasmFS version)

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
65/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
cpp, node.js, wasm
Domain
operating-systems

Research direction

The relevant backend is system/lib/wasmfs/backends/noderawfs_root.cpp, specifically the root initialization referenced in the report. Reproduce test.cc with emcc and Node using both -sNODERAWFS and -sWASMFS; done means /proc/self/exe returns the same Node executable path in both cases.

Written by the indexing model from the issue text.

Description

Please include the following in your bug report:

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 4.0.11 (d3432e7a2a6585331c94b041973fb16c9f332ce4)
clang version 21.0.0git (https:/github.com/llvm/llvm-project 0f0079c29da4b4d5bbd43dced1db9ad6c6d11008)
Target: wasm32-unknown-emscripten
Thread model: posix

Consider this example:

/* test.cc */
#include <stdio.h>
#include <limits.h>
#include <unistd.h>

int main(int argc, char** argv) {
  char buf[PATH_MAX + 1];
  ssize_t len = readlink("/proc/self/exe", buf, sizeof(buf));
  if (len > PATH_MAX) {
    return 2;
  }
  printf("self exe: %s", buf);
  fflush(stdout);
  return 0;
}

% emcc -sEXIT_RUNTIME -sNODERAWFS test.cc && node a.out.js
self exe: /home/trybka/.nvm/versions/node/v22.13.1/bin/node

vs.

% emcc -sEXIT_RUNTIME -sNODERAWFS -sWASMFS test.cc && node a.out.js
self exe:

This is because the "root" of the VFS for NodeRawFS should be /, but when using WasmFS it is . (I assume, via https://github.com/emscripten-core/emscripten/blob/e5c41dbbc93b3a4ab3e0c30935223865facfdbcb/system/lib/wasmfs/backends/noderawfs_root.cpp#L11)

If I change the . to / then it works the same in both cases.

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