Non-zero exit status of shell error during EXIT trap

This commit backports test cases for traps from:
https://github.com/magicant/yash-rs/blob/905576f650221edfb99d4cb6461ce90d3a0489c2/yash-cli/tests/scripted_test/trap-p.sh

A fix is applied to support the new test cases.

NEWS

@@ -4,6 +4,9 @@ History of Yash
 
   - Added support for the "$POST_PROMPT_COMMAND" variable, whose value
     is executed after reading a command line in the interactive shell.
+  - If the shell exits because of a shell error during the EXIT trap,
+    the shell now returns the exit status of the error rather than that
+    of the last command before the EXIT trap.
   - [line-editing] Fixed the spurious error message printed when
     completing after `git config alias.` with the nounset shell option
     enabled.

NEWS.ja

@@ -4,6 +4,9 @@ Yash 更新履歴
 
   - "$POST_PROMPT_COMMAND" に対応。対話モードでコマンドを読むごとに
     変数の値が実行される
+  - EXIT トラップ実行中にリダイレクトエラー等でシェルが終了する際、
+    EXIT トラップ開始直前の終了ステータスではなくエラーの終了
+    ステータスで終了するようにした
   - [行編集] nounset オプション有効時に `git config alias.` に続けて
     補完をしようとするとエラーが出るのを修正
   - [行編集] カーソルがバックスラッシュの直後にある時に補完をすると

exec.c

@@ -1,6 +1,6 @@
 /* Yash: yet another shell */
 /* exec.c: command execution */
-/* (C) 2007-2022 magicant */
+/* (C) 2007-2024 magicant */
 
 /* This program is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -686,7 +686,11 @@ void exec_simple_command(const command_T *c, bool finally_exit)
     plfree(argv, free);
 done:
     if (finally_exit)
-        exit_shell();
+        /* If we're running the EXIT trap and the simple command failed with a
+         * shell error, we should exit with the current exit status indicating
+         * the error rather than the exit status saved just before entering the
+         * EXIT trap, so... */
+        exit_shell_with_status(laststatus); // rather than: exit_shell();
 }
 
 /* Executes the simple command that has no expanded words.

tests/trap-p.tst

@@ -2,6 +2,18 @@
 
 posix="true"
 
+if [ "$(uname)" = Darwin ]; then
+    # On macOS, kill(2) does not appear to run any signal handlers
+    # synchronously, making it impossible for the shell to respond to self-sent
+    # signals at a predictable time. To work around this issue, the kill
+    # built-in is called in a subshell on macOS, using the SIGCHLD signal as a
+    # synchronization trigger.
+    setup <<\__EOF__
+killx() (command kill "$@")
+alias kill=killx
+__EOF__
+fi
+
 test_OE -e USR1 'setting default trap'
 trap - USR1
 kill -s USR1 $$
@@ -107,20 +119,28 @@ __IN__
 ok
 __OUT__
 
-test_O -e n 'fatal shell error in trap'
+test_O -e n 'fatal shell error in signal trap'
 trap 'set <_no_such_file_' INT
 kill -s INT $$
 echo not reached
 __IN__
 
-test_oE -e 0 '$? is restored after trap is executed'
+test_O -e n 'fatal shell error in EXIT trap'
+trap 'set <_no_such_file_' EXIT
+__IN__
+
+test_oE -e 0 '$? is restored after signal trap is executed'
 trap 'false' USR1
 kill -s USR1 $$
 echo $?
 __IN__
 0
 __OUT__
 
+test_E -e 0 'exit status of EXIT trap does not affect exit status of shell'
+trap 'false' EXIT
+__IN__
+
 test_oE 'trap command is not affected by assignment in same simple command' \
     -c 'foo=1 trap "echo EXIT \$foo" EXIT; foo=2; foo=3 echo $foo'
 __IN__