gdb/record: print frame information when exiting a recursive call

Currently,  when GDB is reverse stepping out of a function into the same
function due to a recursive call, it doesn't print frame information, as
reported by PR record/29178. This happens because when the inferior
leaves the current frame, GDB decides to refresh the step information,
clobbering the original step_frame_id, making it impossible to figure
out later on that the frame has been changed.

This commit changes GDB so that, if we notice we're in this exact
situation, we won't refresh the step information.

Because of implementation details, this change can cause some debug
information to be read when it normally wouldn't before, which showed up
as a regression on gdb.dwarf2/dw2-out-of-range-end-of-seq. Since that
isn't a problem, the test was changed to allow for the new output.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29178
Approved-By: Tom Tromey <tom@tromey.com>

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 08c39eb76f31a3cf2fcbaafa71cbf8107716ad38..6ba336dfc872017465f30003218ba7ddb842a76e 100644 (file)
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -7312,6 +7312,11 @@ process_event_stop_test (struct execution_control_state *ecs)
   frame = get_current_frame ();
   gdbarch = get_frame_arch (frame);
 
+  /* Shorthand to make if statements smaller.  */
+  struct frame_id original_frame_id
+    = ecs->event_thread->control.step_frame_id;
+  struct frame_id curr_frame_id = get_frame_id (get_current_frame ());
+
   switch (what.main_action)
     {
     case BPSTAT_WHAT_SET_LONGJMP_RESUME:
@@ -8124,6 +8129,19 @@ process_event_stop_test (struct execution_control_state *ecs)
                               "it's not the start of a statement");
        }
     }
+  else if (execution_direction == EXEC_REVERSE
+         && curr_frame_id != original_frame_id
+         && original_frame_id.code_addr_p && curr_frame_id.code_addr_p
+         && original_frame_id.code_addr == curr_frame_id.code_addr)
+    {
+      /* If we enter here, we're leaving a recursive function call.  In this
+        situation, we shouldn't refresh the step information, because if we
+        do, we'll lose the frame_id of when we started stepping, and this
+        will make GDB not know we need to print frame information.  */
+      refresh_step_info = false;
+      infrun_debug_printf ("reverse stepping, left a recursive call, don't "
+                          "update step info so we remember we left a frame");
+    }
 
   /* We aren't done stepping.
 

diff --git a/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp b/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
index d2c28a87923b74dc09cff8f87084d9f5a43fac11..8b4e79644c17acc9955a889d25c110f1059d4831 100644 (file)
--- a/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-out-of-range-end-of-seq.exp
@@ -84,7 +84,7 @@ if ![runto_main] {
 }
 
 set test "END with address 1 eliminated"
-gdb_test_multiple "maint info line-table $srcfile$" $test {
+gdb_test_multiple "maint info line-table \\b$srcfile$" $test {
     -re -wrap "END *0x0*1 *$hex *Y *\r\n.*" {
        fail $gdb_test_name
     }

diff --git a/gdb/testsuite/gdb.reverse/recursion.c b/gdb/testsuite/gdb.reverse/recursion.c
new file mode 100644 (file)
index 0000000..5ce1c8d
--- /dev/null
+++ b/gdb/testsuite/gdb.reverse/recursion.c
@@ -0,0 +1,44 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2023 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/>.  */
+
+/* Test GDB's ability to handle recursive functions when executing
+   in reverse.  */
+
+/* The recursive foo call must be the first line of the recursive
+   function, to test that we're not stepping too much and skipping
+   multiple calls when we should skip only one.  */
+int
+foo (int x)
+{
+  if (x) return foo (x-1);
+  return 0;
+}
+
+int
+bar (int x)
+{
+  int r = foo (x);
+  return 2*r;
+}
+
+int
+main ()
+{
+  int i = bar (5);
+  int j = foo (5);
+  return 0;                    /* END OF MAIN */
+}

diff --git a/gdb/testsuite/gdb.reverse/recursion.exp b/gdb/testsuite/gdb.reverse/recursion.exp
new file mode 100644 (file)
index 0000000..3fead0e
--- /dev/null
+++ b/gdb/testsuite/gdb.reverse/recursion.exp
@@ -0,0 +1,45 @@
+# Copyright 2008-2023 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 file is part of the GDB testsuite.  It tests reverse stepping
+# out of recursive functions.
+
+require supports_reverse
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
+    return -1
+}
+
+runto_main
+
+if [supports_process_record] {
+    # Activate process record/replay
+    gdb_test_no_output "record" "turn on process record"
+}
+
+set end_of_program [gdb_get_line_number "END OF MAIN" "$srcfile"]
+gdb_breakpoint $end_of_program
+gdb_continue_to_breakpoint ".*$srcfile/$end_of_program.*"
+
+## test if GDB can reverse over a recursive program
+gdb_test "reverse-next" ".*int j = foo.*" "Skipping recursion from outside"
+## setup and next over a recursion for inside a recursive call
+repeat_cmd_until "reverse-step" ".*" ".*foo .x=4.*"
+gdb_test "reverse-next" ".*return foo.*" "Skipping recursion from inside"
+gdb_test "reverse-next" ".*foo .x=5.*" "print frame when stepping out"
+gdb_test "reverse-next" ".*bar .x=5.*" "stepping into a different function"
+gdb_test "reverse-next" "main .. at .*" "stepping back to main"