Refactor code to check for terminal sharing

This refactors the code to check for terminal sharing.
is_gdb_terminal is exported, and sharing_input_terminal_1 is renamed,
slightly refactored, and moved to posix-hdep.c.  A new
Windows-specific implementation of this function is added to
mingw-hdep.c.

MSDN has a warning about GetConsoleProcessList

    This API is not recommended and does not have a virtual terminal
    equivalent. [...] Applications remoting via cross-platform
    utilities and transports like SSH may not work as expected if
    using this API.

However, we believe this isn't likely to be an issue for gdb.

gdb/inferior.h

@@ -167,6 +167,17 @@ extern void default_print_float_info (struct gdbarch *gdbarch,
 				      frame_info_ptr frame,
 				      const char *args);
 
+/* Try to determine whether TTY is GDB's input terminal.  Returns
+   TRIBOOL_UNKNOWN if we can't tell.  */
+
+extern tribool is_gdb_terminal (const char *tty);
+
+/* Helper for sharing_input_terminal.  Try to determine whether pid
+   PID is using the same TTY for input as GDB is.  Returns
+   TRIBOOL_UNKNOWN if we can't tell.  */
+
+extern tribool sharing_input_terminal (int pid);
+
 extern void child_terminal_info (struct target_ops *self, const char *, int);
 
 extern void child_terminal_ours (struct target_ops *self);

gdb/inflow.c

@@ -212,10 +212,9 @@ gdb_save_tty_state (void)
     }
 }
 
-/* Try to determine whether TTY is GDB's input terminal.  Returns
-   TRIBOOL_UNKNOWN if we can't tell.  */
+/* See inferior.h.  */
 
-static tribool
+tribool
 is_gdb_terminal (const char *tty)
 {
   struct stat gdb_tty;
@@ -236,26 +235,6 @@ is_gdb_terminal (const char *tty)
 	  : TRIBOOL_FALSE);
 }
 
-/* Helper for sharing_input_terminal.  Try to determine whether
-   inferior INF is using the same TTY for input as GDB is.  Returns
-   TRIBOOL_UNKNOWN if we can't tell.  */
-
-static tribool
-sharing_input_terminal_1 (inferior *inf)
-{
-  /* Using host-dependent code here is fine, because the
-     child_terminal_foo functions are meant to be used by child/native
-     targets.  */
-#if defined (__linux__) || defined (__sun__)
-  char buf[100];
-
-  xsnprintf (buf, sizeof (buf), "/proc/%d/fd/0", inf->pid);
-  return is_gdb_terminal (buf);
-#else
-  return TRIBOOL_UNKNOWN;
-#endif
-}
-
 /* Return true if the inferior is using the same TTY for input as GDB
    is.  If this is true, then we save/restore terminal flags/state.
 
@@ -287,7 +266,7 @@ sharing_input_terminal (inferior *inf)
 {
   terminal_info *tinfo = get_inflow_inferior_data (inf);
 
-  tribool res = sharing_input_terminal_1 (inf);
+  tribool res = sharing_input_terminal (inf->pid);
 
   if (res == TRIBOOL_UNKNOWN)
     {

gdb/mingw-hdep.c

@@ -21,8 +21,8 @@
 #include "main.h"
 #include "serial.h"
 #include "gdbsupport/event-loop.h"
-
 #include "gdbsupport/gdb_select.h"
+#include "inferior.h"
 
 #include <windows.h>
 
@@ -371,3 +371,32 @@ gdb_console_fputs (const char *linebuf, FILE *fstream)
   last_style = style;
   return 1;
 }
+
+/* See inferior.h.  */
+
+tribool
+sharing_input_terminal (int pid)
+{
+  std::vector<DWORD> results (10);
+  DWORD len = 0;
+  while (true)
+    {
+      len = GetConsoleProcessList (results.data (), results.size ());
+      /* Note that LEN == 0 is a failure, but we can treat it the same
+	 as a "no".  */
+      if (len < results.size ())
+	break;
+
+      results.resize (len);
+    }
+  /* In case the vector was too big.  */
+  results.resize (len);
+  if (std::find (results.begin (), results.end (), pid) != results.end ())
+    {
+      /* The pid is in the list sharing the console, so don't
+	 interrupt the inferior -- it will get the signal itself.  */
+      return TRIBOOL_TRUE;
+    }
+
+  return TRIBOOL_FALSE;
+}

gdb/posix-hdep.c

@@ -19,8 +19,8 @@
 
 #include "defs.h"
 #include "gdbsupport/event-loop.h"
-
 #include "gdbsupport/gdb_select.h"
+#include "inferior.h"
 
 /* Wrapper for select.  Nothing special needed on POSIX platforms.  */
 
@@ -38,3 +38,21 @@ gdb_console_fputs (const char *buf, FILE *f)
 {
   return 0;
 }
+
+/* See inferior.h.  */
+
+tribool
+sharing_input_terminal (int pid)
+{
+  /* Using host-dependent code here is fine, because the
+     child_terminal_foo functions are meant to be used by child/native
+     targets.  */
+#if defined (__linux__) || defined (__sun__)
+  char buf[100];
+
+  xsnprintf (buf, sizeof (buf), "/proc/%d/fd/0", pid);
+  return is_gdb_terminal (buf);
+#else
+  return TRIBOOL_UNKNOWN;
+#endif
+}