[PATCH] Fix Python probe breakpoints

[George Barrett <bob@bob131.so>]

The documentation for the `spec' variant of the gdb.Breakpoint
constructor states that the accepted format is the same as the break
command. However, using the -probe qualifier at the beginning of the
breakpoint specifier causes a GDB internal error as it attempts to
decode a probe location in the wrong code path. Without this
functionality, there doesn't appear to be another way to set breakpoints
on probe points from Python scripts.

This patch changes the constructor to test whether the parsed breakpoint
location is a probe, and if so it uses the probe-specific breakpoint ops
instead.

gdb/ChangeLog:
2019-12-08  George Barrett  <bob@bob131.so>

	Fix Python probe breakpoints.
	* breakpoint.c: Make bkpt_probe_breakpoint_ops non-static.
	* breakpoint.h: Add declaration for bkpt_probe_breakpoint_ops.
	* python/py-breakpoint.c: Use probe ops if the specifier is a
	probe specifier.

gdb/testsuite/ChangeLog:
2019-12-08  George Barrett  <bob@bob131.so>

	Test Python probe breakpoints.
	* gdb.python/py-breakpoint.c: Add probe point.
	* gdb.python/py-breakpoint.exp: Add probe specifier test.
---
 gdb/breakpoint.c                           |  2 +-
 gdb/breakpoint.h                           |  1 +
 gdb/python/py-breakpoint.c                 |  5 ++++-
 gdb/testsuite/gdb.python/py-breakpoint.c   |  7 +++++++
 gdb/testsuite/gdb.python/py-breakpoint.exp | 22 ++++++++++++++++++++++
 5 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index 583f46d852..0e3f6d954a 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -244,7 +244,7 @@ static struct breakpoint_ops momentary_breakpoint_ops;
 struct breakpoint_ops bkpt_breakpoint_ops;
 
 /* Breakpoints set on probes.  */
-static struct breakpoint_ops bkpt_probe_breakpoint_ops;
+struct breakpoint_ops bkpt_probe_breakpoint_ops;
 
 /* Dynamic printf class type.  */
 struct breakpoint_ops dprintf_breakpoint_ops;
diff --git a/gdb/breakpoint.h b/gdb/breakpoint.h
index a9d689d02a..47ca1174ab 100644
--- a/gdb/breakpoint.h
+++ b/gdb/breakpoint.h
@@ -1307,6 +1307,7 @@ extern void tbreak_command (const char *, int);
 extern struct breakpoint_ops base_breakpoint_ops;
 extern struct breakpoint_ops bkpt_breakpoint_ops;
 extern struct breakpoint_ops tracepoint_breakpoint_ops;
+extern struct breakpoint_ops bkpt_probe_breakpoint_ops;
 extern struct breakpoint_ops dprintf_breakpoint_ops;
 
 extern void initialize_breakpoint_ops (void);
diff --git a/gdb/python/py-breakpoint.c b/gdb/python/py-breakpoint.c
index 4170737416..ddd8eeecae 100644
--- a/gdb/python/py-breakpoint.c
+++ b/gdb/python/py-breakpoint.c
@@ -834,7 +834,10 @@ bppy_init (PyObject *self, PyObject *args, PyObject *kwargs)
 			       temporary_bp, bp_breakpoint,
 			       0,
 			       AUTO_BOOLEAN_TRUE,
-			       &bkpt_breakpoint_ops,
+			       (event_location_type (location.get ())
+				 == PROBE_LOCATION
+				    ? &bkpt_probe_breakpoint_ops
+				    : &bkpt_breakpoint_ops),
 			       0, 1, internal_bp, 0);
 	    break;
 	  }
diff --git a/gdb/testsuite/gdb.python/py-breakpoint.c b/gdb/testsuite/gdb.python/py-breakpoint.c
index d102a5f306..bf5bec1200 100644
--- a/gdb/testsuite/gdb.python/py-breakpoint.c
+++ b/gdb/testsuite/gdb.python/py-breakpoint.c
@@ -15,6 +15,10 @@
    You should have received a copy of the GNU General Public License
    along with this program.  If not, see  <http://www.gnu.org/licenses/>.  */
 
+#ifdef USE_PROBES
+#include <sys/sdt.h>
+#endif
+
 int result = 0;
 
 namespace foo_ns
@@ -46,6 +50,9 @@ int main (int argc, char *argv[])
     {
       result += multiply (foo);  /* Break at multiply. */
       result += add (bar); /* Break at add. */
+#ifdef USE_PROBES
+      STAP_PROBE1 (test, result_updated, result);
+#endif
     }
 
   return 0; /* Break at end. */
diff --git a/gdb/testsuite/gdb.python/py-breakpoint.exp b/gdb/testsuite/gdb.python/py-breakpoint.exp
index 625977c0ad..9e3cb475af 100644
--- a/gdb/testsuite/gdb.python/py-breakpoint.exp
+++ b/gdb/testsuite/gdb.python/py-breakpoint.exp
@@ -695,6 +695,27 @@ proc_with_prefix test_bkpt_qualified {} {
 	"-q in spec string and qualified false"
 }
 
+proc_with_prefix test_bkpt_probe {} {
+    global decimal hex testfile srcfile
+
+    if { [prepare_for_testing "failed to prepare" ${testfile}-probes \
+	    ${srcfile} {debug c++ additional_flags=-DUSE_PROBES}] } {
+	untested "breakpoint probe test failed"
+	return -1
+    }
+
+    if ![runto_main] then {
+	fail "cannot run to main."
+	return 0
+    }
+
+    delete_breakpoints
+    gdb_test \
+	"python gdb.Breakpoint(\"-probe test:result_updated\")" \
+	"Breakpoint $decimal at $hex" \
+	"-probe in spec string"
+}
+
 test_bkpt_basic
 test_bkpt_deletion
 test_bkpt_cond_and_cmds
@@ -708,3 +729,4 @@ test_bkpt_pending
 test_bkpt_events
 test_bkpt_explicit_loc
 test_bkpt_qualified
+test_bkpt_probe
-- 
2.23.0