Revert "Latch signal handlers"

This reverts commit 7ed1022cf4.

Fixes #5962.

src/fish_tests.cpp

@@ -1014,7 +1014,7 @@ static void test_cancellation() {
     // Enable fish's signal handling here. We need to make this interactive for fish to install its
     // signal handlers.
     proc_push_interactive(1);
-    signal_set_handlers(true);
+    signal_set_handlers();
 
     // This tests that we can correctly ctrl-C out of certain loop constructs, and that nothing gets
     // printed if we do.

src/proc.cpp

@@ -955,15 +955,18 @@ void proc_sanity_check(const parser_t &parser) {
 
 void proc_push_interactive(int value) {
     ASSERT_IS_MAIN_THREAD();
+    int old = is_interactive;
     interactive_stack.push_back(is_interactive);
     is_interactive = value;
-    signal_set_handlers_once(is_interactive);
+    if (old != value) signal_set_handlers();
 }
 
 void proc_pop_interactive() {
     ASSERT_IS_MAIN_THREAD();
+    int old = is_interactive;
     is_interactive = interactive_stack.back();
     interactive_stack.pop_back();
+    if (is_interactive != old) signal_set_handlers();
 }
 
 void proc_wait_any(parser_t &parser) {

src/reader.cpp

@@ -1744,7 +1744,7 @@ static void reader_interactive_init() {
             }
         }
 
-        signal_set_handlers(shell_is_interactive());
+        signal_set_handlers();
     }
 
     // It shouldn't be necessary to place fish in its own process group and force control

src/signal.cpp

@@ -325,7 +325,7 @@ static void set_interactive_handlers() {
 }
 
 /// Sets up appropriate signal handlers.
-void signal_set_handlers(bool interactive) {
+void signal_set_handlers() {
     struct sigaction act;
     act.sa_flags = 0;
     sigemptyset(&act.sa_mask);
@@ -354,19 +354,11 @@ void signal_set_handlers(bool interactive) {
         FATAL_EXIT();
     }
 
-    if (interactive) {
+    if (shell_is_interactive()) {
         set_interactive_handlers();
     }
 }
 
-void signal_set_handlers_once(bool interactive) {
-    static std::once_flag s_noninter_once;
-    std::call_once(s_noninter_once, signal_set_handlers, false);
-
-    static std::once_flag s_inter_once;
-    if (interactive) std::call_once(s_inter_once, set_interactive_handlers);
-}
-
 void signal_handle(int sig, int do_handle) {
     struct sigaction act;
 

src/signal.h

@@ -17,13 +17,7 @@ const wchar_t *signal_get_desc(int sig);
 void signal_reset_handlers();
 
 /// Set signal handlers to fish default handlers.
-/// If \p interactive is set, apply interactive handlers as well.
+void signal_set_handlers();
-/// Note interactive handlers, once applied, are not cleared; they are a strict superset of
-/// non-interactive handlers.
-void signal_set_handlers(bool interactive);
-
-/// Latch function. This sets signal handlers, but only the first time it is called.
-void signal_set_handlers_once(bool interactive);
 
 /// Tell fish what to do on the specified signal.
 ///