[PATCH v3 2/2] gdb/reverse: Fix stepping over recursive functions

[Bruno Larsen <blarsen@redhat.com>]

Currently, when using GDB to do reverse debugging, if we try to use the
command "reverse next" to skip a recursive function, instead of skipping
all of the recursive calls and stopping in the previous line, we stop at
the second to last recursive call, and need to manually step backwards
until we leave the first call.  This is well documented in PR gdb/16678.

This bug happens because when GDB notices that a reverse step has
entered into a function, GDB will add a step_resume_breakpoint at the
start of the function, then single step out of the prologue once that
breakpoint is hit.  The problem was happening because GDB wouldn't give
that step_resume_breakpoint a frame-id, so the first time the breakpoint
was hit, the inferior would be stopped.  This is fixed by giving the
current frame-id to the breakpoint.

This commit also changes gdb.reverse/step-reverse.c to contain a
recursive function and attempt to both, skip it altogether, and to skip
the second call from inside the first call, as this setup broke a
previous version of the patch.
---
 gdb/infrun.c                                |  2 +-
 gdb/testsuite/gdb.reverse/step-precsave.exp |  6 ++-
 gdb/testsuite/gdb.reverse/step-reverse.c    | 18 ++++++-
 gdb/testsuite/gdb.reverse/step-reverse.exp  | 58 +++++++++++++++++++--
 4 files changed, 76 insertions(+), 8 deletions(-)

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 033699bc3f7..679a0c83ece 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -7133,7 +7133,7 @@ process_event_stop_test (struct execution_control_state *ecs)
 		  sr_sal.pc = ecs->stop_func_start;
 		  sr_sal.pspace = get_frame_program_space (frame);
 		  insert_step_resume_breakpoint_at_sal (gdbarch,
-							sr_sal, null_frame_id);
+							sr_sal, get_stack_frame_id (frame));
 		}
 	    }
 	  else
diff --git a/gdb/testsuite/gdb.reverse/step-precsave.exp b/gdb/testsuite/gdb.reverse/step-precsave.exp
index 0836ed2629f..3279b6ce879 100644
--- a/gdb/testsuite/gdb.reverse/step-precsave.exp
+++ b/gdb/testsuite/gdb.reverse/step-precsave.exp
@@ -86,7 +86,8 @@ gdb_test "step 3" ".*STEP TEST 2.*" "step test 2"
 
 # step over call
 
-gdb_test "step" ".*NEXT OVER THIS CALL.*" "step up to call"
+gdb_test "step" ".*NEXT OVER THIS RECURSION.*" "step up to call"
+gdb_test "next" ".*NEXT OVER THIS CALL.*" "skip recursive call"
 gdb_test "next" ".*STEP INTO THIS CALL.*" "next over call"
 
 # step into call
@@ -280,9 +281,10 @@ gdb_test_multiple "step" "$test_message" {
     }
 }
 
-# next backward over call
+# Next backward over calls.
 
 gdb_test "next" ".*NEXT OVER THIS CALL.*" "reverse next over call"
+gdb_test "next" ".*NEXT OVER THIS RECURSION.*" "reverse next over recursive call"
 
 # step/next backward with count
 
diff --git a/gdb/testsuite/gdb.reverse/step-reverse.c b/gdb/testsuite/gdb.reverse/step-reverse.c
index aea2a98541d..3d647b9b29d 100644
--- a/gdb/testsuite/gdb.reverse/step-reverse.c
+++ b/gdb/testsuite/gdb.reverse/step-reverse.c
@@ -26,6 +26,19 @@ int callee() {		/* ENTER CALLEE */
   return myglob++;	/* ARRIVED IN CALLEE */
 }			/* RETURN FROM CALLEE */
 
+/* We need to make this function take more than a single instruction
+   to run, otherwise it could hide PR gdb/16678, as reverse execution can
+   step over a single-instruction function.  */
+int
+recursive_callee (int val)
+{
+    if (val == 0) return 0;
+    val /= 2;
+    if (val > 1)
+	val++;
+    return recursive_callee (val);	/* RECURSIVE CALL */
+} /* EXIT RECURSIVE FUNCTION */
+
 /* A structure which, we hope, will need to be passed using memcpy.  */
 struct rhomboidal {
   int rather_large[100];
@@ -51,6 +64,9 @@ int main () {
    y = y + 4;
    z = z + 5;	/* STEP TEST 2 */
 
+   /* Test that next goes over recursive calls too */
+   recursive_callee (32); /* NEXT OVER THIS RECURSION */
+
    /* Test that "next" goes over a call */
    callee();	/* NEXT OVER THIS CALL */
 
@@ -60,7 +76,7 @@ int main () {
    /* Test "stepi" */
    a[5] = a[3] - a[4]; /* FINISH TEST */
    callee();	/* STEPI TEST */
-   
+
    /* Test "nexti" */
    callee();	/* NEXTI TEST */
 
diff --git a/gdb/testsuite/gdb.reverse/step-reverse.exp b/gdb/testsuite/gdb.reverse/step-reverse.exp
index 997b62604d5..a540b1f88ce 100644
--- a/gdb/testsuite/gdb.reverse/step-reverse.exp
+++ b/gdb/testsuite/gdb.reverse/step-reverse.exp
@@ -47,9 +47,11 @@ gdb_test "step" ".*STEP TEST 1.*" "step test 1"
 gdb_test "next 2" ".*NEXT TEST 2.*" "next test 2"
 gdb_test "step 3" ".*STEP TEST 2.*" "step test 2"
 
+# Next through a recursive function call.
+gdb_test "next 2" "NEXT OVER THIS CALL.*" "next over recursion"
+
 # step over call
 
-gdb_test "step" ".*NEXT OVER THIS CALL.*" "step up to call"
 gdb_test "next" ".*STEP INTO THIS CALL.*" "next over call"
 
 # step into call
@@ -118,7 +120,7 @@ gdb_test_multiple "stepi" "$test_message" {
 
 set test_message "stepi back from function call"
 gdb_test_multiple "stepi" "$test_message" {
-    -re "NEXTI TEST.*$gdb_prompt $" {
+    -re -wrap "NEXTI TEST.*" {
 	pass "$test_message"
     }
     -re "ARRIVED IN CALLEE.*$gdb_prompt $" {
@@ -143,7 +145,6 @@ gdb_test_multiple "stepi" "$test_message" {
 ###
 
 # Set reverse execution direction
-
 gdb_test_no_output "set exec-dir reverse" "set reverse execution"
 
 # stepi backward thru return and into a function
@@ -243,10 +244,59 @@ gdb_test_multiple "step" "$test_message" {
     }
 }
 
-# next backward over call
+# Next backward over call.
 
 gdb_test "next" ".*NEXT OVER THIS CALL.*" "reverse next over call"
 
+set step_out 0
+gdb_test_multiple "next" "reverse next over recursion" {
+    -re -wrap ".*NEXT OVER THIS RECURSION.*" {
+	pass "$gdb_test_name"
+    }
+    -re -wrap ".*RECURSIVE CALL.*" {
+	fail "$gdb_test_name"
+	set step_out 1
+    }
+}
+if { "$step_out" == 1 } {
+    gdb_test_multiple "next" "stepping out of recursion" {
+	-re -wrap "NEXT OVER THIS RECURSION.*" {
+	    set step_out 0
+	}
+	-re -wrap ".*" {
+	    send_gdb "reverse-next\n"
+	    exp_continue
+	}
+    }
+}
+
+# Step forward over recursion again so we can test stepping over calls
+# inside the recursion itself.
+gdb_test_no_output "set exec-dir forward" "forward again to test recursion"
+gdb_test "next" "NEXT OVER THIS CALL.*" "reverse next over recursion again"
+gdb_test_no_output "set exec-dir reverse" "reverse again to test recursion"
+
+gdb_test "step" ".*EXIT RECURSIVE FUNCTION.*" "enter recursive function"
+set step_pass 1
+gdb_test_multiple "next" "step over recursion inside the recursion" {
+    -re -wrap ".*EXIT RECURSIVE FUNCTION.*" {
+	set step_pass 0
+	send_gdb "next\n"
+	exp_continue
+    }
+    -re -wrap ".*NEXT OVER THIS RECURSION.*" {
+	if {$step_pass} {
+	    pass "step over recursion inside the recursion"
+	} else {
+	    fail "step over recursion inside the recursion"
+	}
+    }
+    -re -wrap ".*" {
+	send_gdb "next\n"
+	exp_continue
+    }
+}
+
 # step/next backward with count
 
 gdb_test "step 3" ".*REVERSE STEP TEST 1.*" "reverse step test 1"
-- 
2.37.2