>From 5174f470b65a61496f66ff3227b8f2dea749fdc2 Mon Sep 17 00:00:00 2001
From: Bruno Haible <bruno@clisp.org>
Date: Sat, 27 Jun 2020 17:04:22 +0200
Subject: [PATCH] Fix invalid uses of siglongjmp.

* poke/pk-repl.c (ctrlc_buf_valid): New variable.
(poke_sigint_handler): If ctrlc_buf_valid is false, terminate the process.
(pk_repl): Set ctrlc_buf_valid to false before installing the signal handler
and to true while ctrlc_buf is valid. Move the sigsetjmp invocation out of the
loop.
---
 poke/pk-repl.c | 42 ++++++++++++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/poke/pk-repl.c b/poke/pk-repl.c
index 08505cb..38a53a5 100644
--- a/poke/pk-repl.c
+++ b/poke/pk-repl.c
@@ -37,7 +37,10 @@
 #include "pk-utils.h"
 #include "pk-map.h"
 
-static sigjmp_buf ctrlc_buf;
+/* The non-local entry point for reentering the REPL.  */
+static sigjmp_buf /*volatile*/ ctrlc_buf;
+/* When nonzero, ctrlc_buf contains a valid value.  */
+static int volatile ctrlc_buf_valid;
 
 /* This function is called repeatedly by the readline library, when
    generating potential command line completions.
@@ -202,13 +205,28 @@ banner (void)
 }
 
 static void
-poke_sigint_handler (int status)
+poke_sigint_handler (int sig)
 {
-  rl_free_line_state ();
-  rl_cleanup_after_signal ();
-  rl_line_buffer[rl_point = rl_end = rl_mark = 0] = 0;
-  printf ("\n");
-  siglongjmp (ctrlc_buf, 1);
+  if (ctrlc_buf_valid)
+    {
+      /* Abort the current command, and return to the REPL.  */
+      rl_free_line_state ();
+      rl_cleanup_after_signal ();
+      rl_line_buffer[rl_point = rl_end = rl_mark = 0] = 0;
+      printf ("\n");
+      siglongjmp (ctrlc_buf, 1);
+    }
+  else
+    {
+      /* The default behaviour for SIGINT is to terminate the process.
+         Let's do that here.  */
+      struct sigaction sa;
+      sa.sa_handler = SIG_DFL;
+      sa.sa_flags = 0;
+      sigemptyset (&sa.sa_mask);
+      sigaction (SIGINT, &sa, NULL);
+      raise (SIGINT);
+    }
 }
 
 /* Return a copy of TEXT, with every instance of the space character
@@ -272,11 +290,12 @@ pk_repl (void)
   banner ();
 
   /* Arrange for the current line to be cancelled on SIGINT.  */
+  ctrlc_buf_valid = 0;
   struct sigaction sa;
   sa.sa_handler = poke_sigint_handler;
   sa.sa_flags = 0;
   sigemptyset (&sa.sa_mask);
-  sigaction (SIGINT, &sa, 0);
+  sigaction (SIGINT, &sa, NULL);
 
 #if defined HAVE_READLINE_HISTORY_H
   char *poke_history = NULL;
@@ -300,13 +319,14 @@ pk_repl (void)
   rl_filename_quote_characters = " ";
   rl_filename_quoting_function = escape_metacharacters;
 
+  sigsetjmp (ctrlc_buf, 1);
+  ctrlc_buf_valid = 1;
+
   while (!poke_exit_p)
     {
       char *prompt;
       char *line;
 
-      while (sigsetjmp (ctrlc_buf, 1) != 0);
-
       pk_term_flush ();
       rl_completion_entry_function = poke_completion_function;
       prompt = pk_prompt ();
@@ -345,6 +365,8 @@ pk_repl (void)
     free (poke_history);
   }
 #endif
+
+  ctrlc_buf_valid = 0;
 }
 
 static int saved_point;
-- 
2.7.4