FLOG to stop depending on the ffi

Prior to this commit, FLOG used the ffi bridge to get the output fd. Invert
this: have fish set the output fd within main. This allows FLOG to be used in
pure Rust tests.

fish-rust/src/ffi.rs

@@ -71,7 +71,6 @@ include_cpp! {
 
     generate!("make_pipes_ffi")
 
-    generate!("get_flog_file_fd")
     generate!("log_extra_to_flog_file")
 
     generate!("fish_wcwidth")

fish-rust/src/ffi_init.rs

@@ -13,6 +13,7 @@ mod ffi2 {
     extern "Rust" {
         fn rust_init();
         fn rust_activate_flog_categories_by_pattern(wc_ptr: wcharz_t);
+        fn rust_set_flog_file_fd(fd: i32);
         fn rust_invalidate_numeric_locale();
     }
 }
@@ -29,6 +30,11 @@ fn rust_activate_flog_categories_by_pattern(wc_ptr: wcharz_t) {
     crate::flog::activate_flog_categories_by_pattern(wc_ptr.into());
 }
 
+/// FFI bridge for setting FLOG file descriptor.
+fn rust_set_flog_file_fd(fd: i32) {
+    crate::flog::set_flog_file_fd(fd as libc::c_int);
+}
+
 /// FFI bridge to invalidate cached locale bits.
 fn rust_invalidate_numeric_locale() {
     locale::invalidate_numeric_locale();

fish-rust/src/flog.rs

@@ -1,11 +1,12 @@
-use crate::ffi::{get_flog_file_fd, wildcard_match};
+use crate::ffi::wildcard_match;
 use crate::parse_util::parse_util_unescape_wildcards;
 use crate::wchar::{widestrs, wstr, WString};
 use crate::wchar_ext::WExt;
 use crate::wchar_ffi::WCharToFFI;
+use libc::c_int;
 use std::io::Write;
-use std::os::unix::io::{FromRawFd, IntoRawFd, RawFd};
-use std::sync::atomic::Ordering;
+use std::os::unix::io::{FromRawFd, IntoRawFd};
+use std::sync::atomic::{AtomicI32, Ordering};
 
 #[rustfmt::skip::macros(category)]
 #[widestrs]
@@ -162,7 +163,7 @@ pub trait FloggableDebug: std::fmt::Debug {
 
 /// Write to our FLOG file.
 pub fn flog_impl(s: &str) {
-    let fd = get_flog_file_fd().0 as RawFd;
+    let fd = get_flog_file_fd();
     if fd < 0 {
         return;
     }
@@ -240,3 +241,14 @@ pub fn activate_flog_categories_by_pattern(wc_ptr: &wstr) {
         }
     }
 }
+
+/// The flog output fd. Defaults to stderr. A value < 0 disables flog.
+static FLOG_FD: AtomicI32 = AtomicI32::new(libc::STDERR_FILENO);
+
+pub fn set_flog_file_fd(fd: c_int) {
+    FLOG_FD.store(fd, Ordering::Relaxed);
+}
+
+pub fn get_flog_file_fd() -> c_int {
+    FLOG_FD.load(Ordering::Relaxed)
+}

src/fish.cpp

@@ -467,6 +467,7 @@ int main(int argc, char **argv) {
         set_cloexec(fileno(debug_output));
         setlinebuf(debug_output);
         set_flog_output_file(debug_output);
+        rust_set_flog_file_fd(get_flog_file_fd());
     }
 
     // No-exec is prohibited when in interactive mode.