[binutils-gdb] Let ui::input_fd be -1

[Tom Tromey <tromey@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=51cacdb50fd2ac2240172a63140e56c0adb41742

commit 51cacdb50fd2ac2240172a63140e56c0adb41742
Author: Tom Tromey <tromey@adacore.com>
Date:   Tue Aug 30 11:30:13 2022 -0600

    Let ui::input_fd be -1
    
    This changes gdb so that, if ui::input_fd is set to -1, then it will
    not be registered with the event loop.  This is useful for the DAP
    support code I wrote, but as it turns out to also be useful to
    Insight, it seems best to check it in separately.

Diff:
---
 gdb/event-top.c | 8 +++++---
 gdb/top.h       | 3 ++-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/gdb/event-top.c b/gdb/event-top.c
index 02b3786320f..4547d614522 100644
--- a/gdb/event-top.c
+++ b/gdb/event-top.c
@@ -533,8 +533,9 @@ stdin_event_handler (int error, gdb_client_data client_data)
 void
 ui::register_file_handler ()
 {
-  add_file_handler (input_fd, stdin_event_handler, this,
-		    string_printf ("ui-%d", num), true);
+  if (input_fd != -1)
+    add_file_handler (input_fd, stdin_event_handler, this,
+		      string_printf ("ui-%d", num), true);
 }
 
 /* See top.h.  */
@@ -542,7 +543,8 @@ ui::register_file_handler ()
 void
 ui::unregister_file_handler ()
 {
-  delete_file_handler (input_fd);
+  if (input_fd != -1)
+    delete_file_handler (input_fd);
 }
 
 /* Re-enable stdin after the end of an execution command in
diff --git a/gdb/top.h b/gdb/top.h
index 5c1db84b2ce..9ea07262c39 100644
--- a/gdb/top.h
+++ b/gdb/top.h
@@ -118,7 +118,8 @@ struct ui
   FILE *errstream;
 
   /* The file descriptor for the input stream, so that we can register
-     it with the event loop.  */
+     it with the event loop.  This can be set to -1 to prevent this
+     registration.  */
   int input_fd;
 
   /* Whether ISATTY returns true on input_fd.  Cached here because