[gdb] Fix handling of aborted inferior call

PR gdb/33069 reports the following behavior:
...
$ gdb -q ls -ex starti -ex "b *1"
Reading symbols from ls...
(No debugging symbols found in ls)
Starting program: /usr/bin/ls

Program stopped.
0x00007ffff7fe4f00 in _start () from /lib64/ld-linux-x86-64.so.2
Breakpoint 1 at 0x1
(gdb) p (int)strlen("abc")
Warning:
Cannot insert breakpoint 1.
Cannot access memory at address 0x1

Command aborted.
An error occurred while in a function called from GDB.
Evaluation of the expression containing the function
(malloc@plt) will be abandoned.
When the function is done executing, GDB will silently stop.

[1]+  Stopped                 gdb -q ls -ex starti -ex "b *1"
$ fg
gdb -q ls -ex starti -ex "b *1"
(gdb)
...
with gdb being unresponsive to further input.

PR gdb/33068 reports a similar problem, but using gdbserver, and in that case
gdb doesn't go into the background, but is likewise unresponsive.

This is a regression since commit b1c0ab20809 ("gdb: avoid double stop after
failed breakpoint condition check"), and consequently since release gdb 14.1.

The commit changed this in run_inferior_call:
...
   if (current_ui->prompt_state == PROMPT_BLOCKED)
-    current_ui->unregister_file_handler ();
-  else
-    current_ui->register_file_handler ();
+    {
+      if (call_thread->thread_fsm ()->finished_p ())
+	async_disable_stdin ();
+      else
+	async_enable_stdin ();
+    }
...
which means current_ui->register_file_handler is no longer called in the
current_ui->prompt_state == PROMPT_NEEDED case.

Fix this by:
- restoring this behavior, fixing the unresponsiveness, and
- adding target_terminal::ours alongside it, fixing the problem that gdb goes
  into the background.

Add a new test-case gdb.base/infcall-failure-2.exp, a regression test for the
unresponsiveness issue.  The problem of gdb going into the background did not
reproduce in the test-case.

Tested on x86_64-linux.

Reviewed-By: Keith Seitz <keiths@redhat.com>

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33068
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=33069

2 files changed, 46 insertions, 3 deletions

diff --git a/gdb/infcall.c b/gdb/infcall.c
index db6d677..c4b4c8f 100644
--- a/gdb/infcall.c
+++ b/gdb/infcall.c
@@ -887,9 +887,9 @@ run_inferior_call (std::unique_ptr<call_thread_fsm> sm,
      call async_enable_stdin.  This changes the prompt state to
      PROMPT_NEEDED.
 
-     If the previous prompt state was PROMPT_NEEDED, then as
-     async_enable_stdin has already been called, nothing additional
-     needs to be done here.  */
+     If the previous prompt state was PROMPT_NEEDED, then async_enable_stdin
+     may or may not have been called, so do the same changes as in
+     async_enable_stdin.  */
   if (current_ui->prompt_state == PROMPT_BLOCKED)
     {
       if (call_thread->thread_fsm ()->finished_p ())
@@ -897,6 +897,12 @@ run_inferior_call (std::unique_ptr<call_thread_fsm> sm,
       else
 	async_enable_stdin ();
     }
+  else if (current_ui->prompt_state == PROMPT_NEEDED)
+    {
+      /* Copied from async_enable_stdin.  */
+      target_terminal::ours ();
+      current_ui->register_file_handler ();
+    }
 
   /* If the infcall does NOT succeed, normal_stop will have already
      finished the thread states.  However, on success, normal_stop
diff --git a/gdb/testsuite/gdb.base/infcall-failure-2.exp b/gdb/testsuite/gdb.base/infcall-failure-2.exp
new file mode 100644
index 0000000..2a7d784
--- /dev/null
+++ b/gdb/testsuite/gdb.base/infcall-failure-2.exp
@@ -0,0 +1,37 @@
+# Copyright 2025 Free Software Foundation, Inc.
+
+# 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
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+standard_testfile infcall-failure.c
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile] == -1 } {
+    return
+}
+
+if { ![runto_main] } {
+    return
+}
+
+if { ![gdb_breakpoint "*0x1" message] } {
+    return
+}
+
+gdb_test "p foo ()" \
+    [multi_line \
+	 [string_to_regexp "Command aborted."] \
+	 ".*" ]
+
+# Check that gdb is still responsive.  Regression test for PR gdb/33068.
+gdb_test "p 1 + 1" \
+    " = 2"