record-btrace: fix assertion when enabling recording after re-run

Reading symbols from /bin/true...(no debugging symbols found)...done.
(gdb) b _start
Function "_start" not defined.
Make breakpoint pending on future shared library load? (y or [n]) y
Breakpoint 1 (_start) pending.
(gdb) r
Starting program: /bin/true

Breakpoint 1, 0x00000039a0400af0 in _start () from /lib64/ld-linux-x86-64.so.2
(gdb) rec b
(gdb) r
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /bin/true

Breakpoint 1, 0x00000039a0400af0 in _start () from /lib64/ld-linux-x86-64.so.2
(gdb) rec b
gdb/record-btrace.c:154: internal-error: record_btrace_open:
 Assertion `record_btrace_thread_observer == NULL' failed.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n)


gdb/
	* record-btrace.c (record_btrace_close): Call
	record_btrace_auto_disable.

testsuite/
	* gdb.btrace/enable.exp: Add regression test.

1 files changed, 11 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.btrace/enable.exp b/gdb/testsuite/gdb.btrace/enable.exp
index f3acbf8..2e23e41 100644
--- a/gdb/testsuite/gdb.btrace/enable.exp
+++ b/gdb/testsuite/gdb.btrace/enable.exp
@@ -82,3 +82,14 @@ if ![runto_main] {
 if ![runto_main] {
     return -1
 }
+
+# make sure record-btrace can be enabled after re-run
+clean_restart $testfile
+if ![runto_main] {
+    return -1
+}
+gdb_test_no_output "record btrace"
+if ![runto_main] {
+    return -1
+}
+gdb_test_no_output "record btrace" "enable after re-run"