message: Write name and value for each env var
diff: @@ -16,17 +16,19 @@ impl EnvVars {
  ) {
  if ecx.machine.communicate {
  for (name, value) in std::env::vars() {
  - let value = alloc_env_value(value.as_bytes(), ecx.memory_mut());
  - ecx.machine.env_vars.map.insert(name.into_bytes(), value);
  + let var_ptr = alloc_env_var(name.as_bytes(), value.as_bytes(), ecx.memory_mut());
  + ecx.machine.env_vars.map.insert(name.into_bytes(), var_ptr);
  }
  }
  }
  }
  -fn alloc_env_value<'mir, 'tcx>(
  - bytes: &[u8],
  +fn alloc_env_var<'mir, 'tcx>(
  + name: &[u8],
  + value: &[u8],
  memory: &mut Memory<'mir, 'tcx, Evaluator<'tcx>>,
  ) -> Pointer<Tag> {
  + let bytes = [name, b"=", value].concat();
  let tcx = {memory.tcx.tcx};
  let length = bytes.len() as u64;
  // `+1` for the null terminator.
  @@ -57,7 +59,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  let name_ptr = this.read_scalar(name_op)?.not_undef()?;
  let name = this.memory().read_c_str(name_ptr)?;
  Ok(match this.machine.env_vars.map.get(name) {
  - Some(&var) => Scalar::Ptr(var),
  + Some(var_ptr) => Scalar::Ptr(var_ptr.offset(Size::from_bytes(name.len() as u64 + 1), this)?),
  None => Scalar::ptr_null(&*this.tcx),
  })
  }
  @@ -80,8 +82,8 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  }
  }
  if let Some((name, value)) = new {
  - let value_copy = alloc_env_value(&value, this.memory_mut());
  - if let Some(var) = this.machine.env_vars.map.insert(name.to_owned(), value_copy) {
  + let var_ptr = alloc_env_var(&name, &value, this.memory_mut());
  + if let Some(var) = this.machine.env_vars.map.insert(name.to_owned(), var_ptr) {
  this.memory_mut().deallocate(var, None, MiriMemoryKind::Env.into())?;
  }
  Ok(0)
  