[PATCH v2] gdb/breakpoint: remove assertion when printing internal breakpoints without locspecs

["Sébastien Darche" <sdarche@efficios.com>]

When debugging gdb with `set debug breakpoint on`, gdb would crash if
the inferior happened to unload (through dlclose ()) a shared library
that contains jit debugging symbols:

	../../gdb/breakpoint.c:6473: internal-error: print_breakpoint_location:
	Assertion `b->locspec != nullptr || (!user_breakpoint_p (b) && (b->type
	== bp_shlib_event || b->type == bp_thread_event))' failed.
	A problem internal to GDB has been detected [...]

This assertion was added in commit 5770f68 ("gdb: handle empty locspec
when printing breakpoints"). The assumption for this assert is that the
user may not call any (gdb-)debugging command between the time a shared
library is marked (bp_location->shlib_disabled is set) and the
breakpoint is actually removed. This would be true if the user called
`maint info breakpoints` as explained in the original commit message.

However, if `set debug breakpoint on` is called, gdb prints debugging
info as the shared library is being unloaded. The ~jiter_objfile_data
dtor deletes the breakpoint, which calls remove_breakpoint_1 on the
bp_location in the recently unloaded shared object. Since `debug
breakpoint` is enabled, we go through print_breakpoint_location with the
bp_location's shlib_disabled flag set, which results in the assert
above.

This commit removes the assertion as it is not true in all cases. I've
also included a minimal test case that loads a shared library with a
__jit_debug_register_code symbol. The test fails with the assert.

Change-Id: Ia19c84f194a6f0c10315548c7f423bfd86ef0266
---
 gdb/breakpoint.c                          | 17 -------
 gdb/testsuite/gdb.base/jit-unload-solib.c | 21 ++++++++
 gdb/testsuite/gdb.base/jit-unload.c       | 45 ++++++++++++++++
 gdb/testsuite/gdb.base/jit-unload.exp     | 62 +++++++++++++++++++++++
 4 files changed, 128 insertions(+), 17 deletions(-)
 create mode 100644 gdb/testsuite/gdb.base/jit-unload-solib.c
 create mode 100644 gdb/testsuite/gdb.base/jit-unload.c
 create mode 100644 gdb/testsuite/gdb.base/jit-unload.exp

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 101dc57ee6b..85c4ffc3171 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -6457,23 +6457,6 @@ print_breakpoint_location (const breakpoint *b, const bp_location *loc)
     }
   else
     {
-      /* Internal breakpoints don't have a locspec string, but can become
-	 pending if the shared library the breakpoint is in is unloaded.
-	 For most internal breakpoint types though, after unloading the
-	 shared library, the breakpoint will be deleted and never recreated
-	 (see internal_breakpoint::re_set).  But for two internal
-	 breakpoint types bp_shlib_event and bp_thread_event this is not
-	 true.  Usually we don't expect the libraries that contain these
-	 breakpoints to ever be unloaded, but a buggy inferior might do
-	 such a thing, in which case GDB should be prepared to handle this
-	 case.
-
-	 If these two breakpoint types become pending then there will be no
-	 locspec string.  */
-      gdb_assert (b->locspec != nullptr
-		  || (!user_breakpoint_p (b)
-		      && (b->type == bp_shlib_event
-			  || b->type == bp_thread_event)));
       const char *locspec_str
 	= (b->locspec != nullptr ? b->locspec->to_string () : "");
       uiout->field_string ("pending", locspec_str);
diff --git a/gdb/testsuite/gdb.base/jit-unload-solib.c b/gdb/testsuite/gdb.base/jit-unload-solib.c
new file mode 100644
index 00000000000..3cf2c580320
--- /dev/null
+++ b/gdb/testsuite/gdb.base/jit-unload-solib.c
@@ -0,0 +1,21 @@
+/* This test program is part of GDB, the GNU debugger.
+
+   Copyright 2026 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/>.  */
+
+/* This simulates a JIT library.  */
+
+
+#include "jit-protocol.h"
diff --git a/gdb/testsuite/gdb.base/jit-unload.c b/gdb/testsuite/gdb.base/jit-unload.c
new file mode 100644
index 00000000000..92dfa16c055
--- /dev/null
+++ b/gdb/testsuite/gdb.base/jit-unload.c
@@ -0,0 +1,45 @@
+/* This test program is part of GDB, the GNU debugger.
+
+   Copyright 2026 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/>.  */
+
+/* Simulate loading of a library JIT code.  */
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#ifdef __WIN32__
+#include <windows.h>
+#define dlopen(name, mode) LoadLibrary (TEXT (name))
+#define dlclose(handle) FreeLibrary (handle)
+#else
+#include <dlfcn.h>
+#endif
+
+
+int
+main (void)
+{
+  void *handle = dlopen (SHLIB_NAME, RTLD_NOW);
+
+  if (handle == NULL)
+    {
+      fprintf (stderr, "%s\n", dlerror ());
+      exit (1);
+    }
+
+  dlclose (handle);
+  return 0;
+}
diff --git a/gdb/testsuite/gdb.base/jit-unload.exp b/gdb/testsuite/gdb.base/jit-unload.exp
new file mode 100644
index 00000000000..a5f9adbd76c
--- /dev/null
+++ b/gdb/testsuite/gdb.base/jit-unload.exp
@@ -0,0 +1,62 @@
+# Copyright 2026 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/>.
+
+# This test checks that gdb does not assert when unloading a shared library
+# that defines a __jit_debug_register_code if `set debug breakpoint on` is set.
+
+require allow_shlib_tests
+
+standard_testfile .c -solib.c
+set lib_testfile ${testfile}-lib
+set lib_binfile [standard_output_file $lib_testfile]
+
+if { [build_executable "build shlib" $lib_testfile $srcfile2 \
+	{debug shlib}] == -1 } {
+    return
+}
+
+set lib_testfile_on_target [gdb_download_shlib $lib_binfile]
+
+set options [list \
+		debug \
+		shlib_load \
+		additional_flags=-DSHLIB_NAME=\"${lib_testfile_on_target}\"]
+
+if { [prepare_for_testing "build main file" $testfile $srcfile \
+	$options] == -1 } {
+    return
+}
+
+if { ![runto_main] } {
+    return
+}
+
+gdb_test_no_output "set debug breakpoint on"
+
+set saw_exit false
+gdb_test_multiple "continue" unload {
+    -re "^\\\[Inferior $decimal \[^\r\n\]+ exited normally\\\]\r\n" {
+	set saw_exit true
+	exp_continue
+    }
+
+    -re "^$gdb_prompt $" {
+	gdb_assert ${saw_exit} $gdb_test_name
+    }
+
+    -re "^\[^\r\n\]*\r\n" {
+	exp_continue
+    }
+}
-- 
2.54.0