Unable to use emscripten env (vs wasi) in standalone_wasm

[jedbrown]

I would like to build WASM standalone with access to the file system, but wasmer fails to find imports when using emscripten's env (including failing to import WASI when env symbols are present). Is there a way to get wasmer to handle this or a different tool that can run in this way? I can build these examples to a.js and run with node a.js, but would prefer the STANDALONE_WASM mode.

Failing to find "wasi_snapshot_preview1"."proc_exit" when "env"."__syscall_rmdir" is needed.

$ cat a.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main() {
  rmdir("does-not-exist");
  char *x = malloc(42);
  free(x);
  puts("Hello");
  return 0;
}
$ emcc a.c -o a.wasm
$ wasmer a.wasm
error: failed to run `a.wasm`
╰─▶ 1: Error while importing "wasi_snapshot_preview1"."proc_exit": unknown import. Expected Function(FunctionType { params: [I32], results: [] })
$ wasmer inspect a.wasm
Type: wasm
Size: 10.6 KB
Imports:
  Functions:
    "wasi_snapshot_preview1"."proc_exit": [I32] -> []
    "env"."__syscall_rmdir": [I32] -> [I32]
    "wasi_snapshot_preview1"."fd_write": [I32, I32, I32, I32] -> [I32]
  Memories:
  Tables:
  Globals:
Exports:
  Functions:
    "_start": [] -> []
    "__errno_location": [] -> [I32]
    "emscripten_stack_init": [] -> []
    "emscripten_stack_get_free": [] -> [I32]
    "emscripten_stack_get_base": [] -> [I32]
    "emscripten_stack_get_end": [] -> [I32]
    "stackSave": [] -> [I32]
    "stackRestore": [I32] -> []
    "stackAlloc": [I32] -> [I32]
  Memories:
    "memory": not shared (256 pages..256 pages)
  Tables:
    "__indirect_function_table": FuncRef (5..5)
  Globals:

The above will also fail if you remove everything but malloc and build with -sALLOW_MEMORY_GROWTH because that references "env"."emscripten_notify_memory_growth".

---

This demonstrates that we fail to find env symbols even when there are no WASI symbols needed.

Details

$ cat b.c
#include <unistd.h>

__attribute__((used)) void f_using_env() { rmdir("does-not-exist"); }
$ emcc --no-entry b.c -o b.wasm
$ wasmer b.wasm
error: failed to run `b.wasm`
╰─▶ 1: Error while importing "env"."__syscall_rmdir": unknown import. Expected Function(FunctionType { params: [I32], results: [I32] })
$ wasmer inspect b.wasm
Type: wasm
Size: 563 B
Imports:
  Functions:
    "env"."__syscall_rmdir": [I32] -> [I32]
  Memories:
  Tables:
  Globals:
Exports:
  Functions:
    "f_using_env": [] -> []
    "_initialize": [] -> []
    "__errno_location": [] -> [I32]
    "emscripten_stack_init": [] -> []
    "emscripten_stack_get_free": [] -> [I32]
    "emscripten_stack_get_base": [] -> [I32]
    "emscripten_stack_get_end": [] -> [I32]
    "stackSave": [] -> [I32]
    "stackRestore": [I32] -> []
    "stackAlloc": [I32] -> [I32]
  Memories:
    "memory": not shared (256 pages..256 pages)
  Tables:
    "__indirect_function_table": FuncRef (2..2)
  Globals:

---

$ wasmer --version
wasmer 3.0.0-beta.2
$ emcc --version
emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.24-git (68a9f990429e0bcfb63b1cde68bad792554350a5)
Copyright (C) 2014 the Emscripten authors (see AUTHORS.txt)
This is free and open source software under the MIT license.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.