We may abort the process of detaching threads with multiple SIGINTs - which are
being sent during a testcase terminating its child GDB.

Some of the threads may not be properly PTRACE_DETACHed which hurts if they
should have been detached with SIGSTOP (as they are accidentally left running
on the debugger termination).

Index: gdb-7.12.50.20170207/gdb/defs.h
===================================================================
--- gdb-7.12.50.20170207.orig/gdb/defs.h	2017-02-26 21:11:35.654350580 +0100
+++ gdb-7.12.50.20170207/gdb/defs.h	2017-02-26 21:11:52.932473129 +0100
@@ -169,6 +169,10 @@
 /* Flag that function quit should call quit_force.  */
 extern volatile int sync_quit_force_run;
 
+#ifdef NEED_DETACH_SIGSTOP
+extern int quit_flag_cleanup;
+#endif
+
 extern void quit (void);
 
 /* Helper for the QUIT macro.  */
Index: gdb-7.12.50.20170207/gdb/extension.c
===================================================================
--- gdb-7.12.50.20170207.orig/gdb/extension.c	2017-02-26 21:11:35.655350587 +0100
+++ gdb-7.12.50.20170207/gdb/extension.c	2017-02-26 21:11:52.933473136 +0100
@@ -830,6 +830,11 @@
   int i, result = 0;
   const struct extension_language_defn *extlang;
 
+#ifdef NEED_DETACH_SIGSTOP
+  if (quit_flag_cleanup)
+    return 0;
+#endif
+
   ALL_ENABLED_EXTENSION_LANGUAGES (i, extlang)
     {
       if (extlang->ops->check_quit_flag != NULL)
Index: gdb-7.12.50.20170207/gdb/top.c
===================================================================
--- gdb-7.12.50.20170207.orig/gdb/top.c	2017-02-26 21:11:35.655350587 +0100
+++ gdb-7.12.50.20170207/gdb/top.c	2017-02-26 21:11:52.933473136 +0100
@@ -1619,7 +1619,13 @@
   qt.args = NULL;
   qt.from_tty = from_tty;
 
+#ifndef NEED_DETACH_SIGSTOP
   /* We want to handle any quit errors and exit regardless.  */
+#else
+  /* We want to handle any quit errors and exit regardless but we should never
+     get user-interrupted to properly detach the inferior.  */
+  quit_flag_cleanup = 1;
+#endif
 
   /* Get out of tfind mode, and kill or detach all inferiors.  */
   TRY
Index: gdb-7.12.50.20170207/gdb/utils.c
===================================================================
--- gdb-7.12.50.20170207.orig/gdb/utils.c	2017-02-26 21:11:35.657350601 +0100
+++ gdb-7.12.50.20170207/gdb/utils.c	2017-02-26 21:11:52.934473143 +0100
@@ -106,6 +106,13 @@
 
 int job_control;
 
+#ifdef NEED_DETACH_SIGSTOP
+/* Nonzero means we are already processing the quitting cleanups and we should
+   no longer get aborted.  */
+
+int quit_flag_cleanup;
+#endif
+
 /* Nonzero means that strings with character values >0x7F should be printed
    as octal escapes.  Zero means just print the value (e.g. it's an
    international character, and the terminal or window can cope.)  */