Don't use argv[0] directly when computing executable path

When "status fish-path" fails, we fall back to argv[0],
hoping that it contains an absolute path to fish, or at
least is equal to "fish" (which can happen on OpenBSD, see
https://github.com/rust-lang/rust/issues/60560#issuecomment-489425888).

I don't think it makes sense to duplicate logic that's probably
already in std::env::current_exe().

src/bin/fish.rs

@@ -490,7 +490,7 @@ fn throwing_main() -> i32 {
 
     // If we're not executing, there's no need to find the config.
     let config_paths = if !opts.no_exec {
-        let config_paths = ConfigPaths::new(&args[0]);
+        let config_paths = ConfigPaths::new();
         env_init(
             Some(&config_paths),
             /* do uvars */ !opts.no_config,

src/builtins/status.rs

@@ -1,7 +1,7 @@
 use std::os::unix::prelude::*;
 
 use super::prelude::*;
-use crate::common::{PROGRAM_NAME, bytes2wcstring, get_executable_path};
+use crate::common::{PROGRAM_NAME, bytes2wcstring, get_fish_path};
 use crate::future_feature_flags::{self as features, feature_test};
 use crate::proc::{
     JobControl, get_job_control_mode, get_login, is_interactive_session, set_job_control_mode,
@@ -718,7 +718,7 @@ pub fn status(parser: &Parser, streams: &mut IoStreams, args: &mut [&wstr]) -> B
                     streams.out.append_char('\n');
                 }
                 STATUS_FISH_PATH => {
-                    let path = get_executable_path("fish");
+                    let path = get_fish_path();
                     if path.is_empty() {
                         streams.err.append(sprintf!(
                             "%s: Could not get executable path: '%s'\n",

src/common.rs

@@ -25,7 +25,7 @@
 use std::mem;
 use std::ops::{Deref, DerefMut};
 use std::os::unix::prelude::*;
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
 use std::sync::atomic::{AtomicI32, AtomicU32, Ordering};
 use std::sync::{Arc, MutexGuard};
 use std::time;
@@ -1578,9 +1578,10 @@ pub fn valid_var_name(s: &wstr) -> bool {
 }
 
 /// Get the absolute path to the fish executable itself
-pub fn get_executable_path(argv0: impl AsRef<Path>) -> PathBuf {
+pub fn get_fish_path() -> PathBuf {
     let Ok(path) = std::env::current_exe() else {
-        return argv0.as_ref().to_owned();
+        assert!(PROGRAM_NAME.get().unwrap() == "fish");
+        return PathBuf::from("fish");
     };
     if path.exists() {
         return path;

src/env/config_paths.rs

@@ -1,10 +1,6 @@
-use crate::common::BUILD_DIR;
-use crate::common::wcs2bytes;
-use crate::wchar::prelude::*;
-use crate::{FLOG, FLOGF, common::get_executable_path};
+use crate::common::{BUILD_DIR, get_fish_path};
+use crate::{FLOG, FLOGF};
 use fish_build_helper::workspace_root;
-use std::ffi::OsString;
-use std::os::unix::ffi::OsStringExt;
 use std::path::PathBuf;
 
 /// A struct of configuration directories, determined in main() that fish will optionally pass to
@@ -23,9 +19,8 @@ pub struct ConfigPaths {
 const DOC_DIR: &str = env!("DOCDIR");
 
 impl ConfigPaths {
-    pub fn new(argv0: &wstr) -> Self {
-        let argv0 = PathBuf::from(OsString::from_vec(wcs2bytes(argv0)));
-        let exec_path = get_executable_path(argv0);
+    pub fn new() -> Self {
+        let exec_path = get_fish_path();
         FLOG!(config, format!("executable path: {}", exec_path.display()));
         let paths = Self::from_exec_path(exec_path);
         FLOGF!(