Don't elide all inlined frames

This patch essentially causes GDB to treat inlined frames like "normal"
frames from the user's perspective.  This means, for example, that when a
user sets a breakpoint in an inlined function, GDB will now actually stop
"in" that function.

Using the test case from breakpoints/17534,

3	static inline void NVIC_EnableIRQ(int IRQn)
4	{
5	  volatile int y;
6	  y = IRQn;
7	}
8
9	__attribute__( ( always_inline ) ) static inline void __WFI(void)
10	{
11	    __asm volatile ("nop");
12	}
13
14	int main(void) {
15
16	    x= 42;
17
18	    if (x)
19	      NVIC_EnableIRQ(16);
20	    else
21	      NVIC_EnableIRQ(18);
(gdb) b NVIC_EnableIRQ
Breakpoint 1 at 0x4003e4: NVIC_EnableIRQ. (2 locations)
(gdb) r
Starting program: 17534

Breakpoint 1, main () at 17534.c:19
19	      NVIC_EnableIRQ(16);

Because skip_inline_frames currently skips every inlined frame, GDB "stops"
in the caller.  This patch adds a new parameter to skip_inline_frames
that allows us to pass in a bpstat stop chain.  The breakpoint locations
on the stop chain can be used to determine if we've stopped inside an inline
function (due to a user breakpoint).  If we have, we do not elide the frame.

With this patch, GDB now reports that the inferior has stopped inside the
inlined function:

(gdb) r
Starting program: 17534

Breakpoint 1, NVIC_EnableIRQ (IRQn=16) at 17534.c:6
6	  y = IRQn;

Many thanks to Jan and Pedro for guidance on this.

gdb/ChangeLog:

	* breakpoint.c (build_bpstat_chain): New function, moved from
	bpstat_stop_status.
	(bpstat_stop_status): Add optional parameter, `stop_chain'.
	If no stop chain is passed, call build_bpstat_chain to build it.
	* breakpoint.h (build_bpstat_chain): Declare.
	(bpstat_stop_status): Move documentation here from breakpoint.c.
	* infrun.c (handle_signal_stop): Before eliding inlined frames,
	build the stop chain and pass it to skip_inline_frames.
	Pass this stop chain to bpstat_stop_status.
	* inline-frame.c: Include breakpoint.h.
	(stopped_by_user_bp_inline_frame): New function.
	(skip_inline_frames): Add parameter `stop_chain'.
	Move documention to inline-frame.h.
	If non-NULL, use stopped_by_user_bp_inline_frame to determine
	whether the frame should be elided.
	* inline-frame.h (skip_inline_frames): Add parameter `stop_chain'.
	Add moved documentation and update for new parameter.

gdb/testsuite/ChangeLog:

	* gdb.ada/bp_inlined_func.exp: Update inlined frame locations
	in expected breakpoint stop locations.
	* gdb.dwarf2/implptr.exp (implptr_test_baz): Use up/down to
	move to proper scope to test variable values.
	* gdb.opt/inline-break.c (inline_func1, not_inline_func1)
	(inline_func2, not_inline_func2, inline_func3, not_inline_func3):
	New functions.
	(main): Call not_inline_func3.
	* gdb.opt/inline-break.exp: Start inferior and set breakpoints at
	inline_func1, inline_func2, and inline_func3.  Test that when each
	breakpoint is hit, GDB properly reports both the stop location
	and the backtrace. Repeat tests for temporary breakpoints.

Author: shtiek

gdb/ChangeLog

@@ -1,3 +1,23 @@
+2018-05-17  Keith Seitz  <keiths@redhat.com>
+
+	* breakpoint.c (build_bpstat_chain): New function, moved from
+	bpstat_stop_status.
+	(bpstat_stop_status): Add optional parameter, `stop_chain'.
+	If no stop chain is passed, call build_bpstat_chain to build it.
+	* breakpoint.h (build_bpstat_chain): Declare.
+	(bpstat_stop_status): Move documentation here from breakpoint.c.
+	* infrun.c (handle_signal_stop): Before eliding inlined frames,
+	build the stop chain and pass it to skip_inline_frames.
+	Pass this stop chain to bpstat_stop_status.
+	* inline-frame.c: Include breakpoint.h.
+	(stopped_by_user_bp_inline_frame): New function.
+	(skip_inline_frames): Add parameter `stop_chain'.
+	Move documention to inline-frame.h.
+	If non-NULL, use stopped_by_user_bp_inline_frame to determine
+	whether the frame should be elided.
+	* inline-frame.h (skip_inline_frames): Add parameter `stop_chain'.
+	Add moved documentation and update for new parameter.
+
 2018-05-17  Simon Marchi  <simon.marchi@ericsson.com>
 
 	PR cli/14975

gdb/breakpoint.c

@@ -5308,54 +5308,21 @@ need_moribund_for_location_type (struct bp_location *loc)
 	      && !target_supports_stopped_by_hw_breakpoint ()));
 }
 
-
-/* Get a bpstat associated with having just stopped at address
-   BP_ADDR in thread PTID.
-
-   Determine whether we stopped at a breakpoint, etc, or whether we
-   don't understand this stop.  Result is a chain of bpstat's such
-   that:
-
-   if we don't understand the stop, the result is a null pointer.
-
-   if we understand why we stopped, the result is not null.
-
-   Each element of the chain refers to a particular breakpoint or
-   watchpoint at which we have stopped.  (We may have stopped for
-   several reasons concurrently.)
-
-   Each element of the chain has valid next, breakpoint_at,
-   commands, FIXME??? fields.  */
+/* See breakpoint.h.  */
 
 bpstat
-bpstat_stop_status (const address_space *aspace,
-		    CORE_ADDR bp_addr, ptid_t ptid,
+build_bpstat_chain (const address_space *aspace, CORE_ADDR bp_addr,
 		    const struct target_waitstatus *ws)
 {
-  struct breakpoint *b = NULL;
-  struct bp_location *bl;
-  struct bp_location *loc;
-  /* First item of allocated bpstat's.  */
+  struct breakpoint *b;
   bpstat bs_head = NULL, *bs_link = &bs_head;
-  /* Pointer to the last thing in the chain currently.  */
-  bpstat bs;
-  int ix;
-  int need_remove_insert;
-  int removed_any;
-
-  /* First, build the bpstat chain with locations that explain a
-     target stop, while being careful to not set the target running,
-     as that may invalidate locations (in particular watchpoint
-     locations are recreated).  Resuming will happen here with
-     breakpoint conditions or watchpoint expressions that include
-     inferior function calls.  */
 
   ALL_BREAKPOINTS (b)
     {
       if (!breakpoint_enabled (b))
 	continue;
 
-      for (bl = b->loc; bl != NULL; bl = bl->next)
+      for (bp_location *bl = b->loc; bl != NULL; bl = bl->next)
 	{
 	  /* For hardware watchpoints, we look only at the first
 	     location.  The watchpoint_check function will work on the
@@ -5374,8 +5341,8 @@ bpstat_stop_status (const address_space *aspace,
 	  /* Come here if it's a watchpoint, or if the break address
 	     matches.  */
 
-	  bs = new bpstats (bl, &bs_link);	/* Alloc a bpstat to
-						   explain stop.  */
+	  bpstat bs = new bpstats (bl, &bs_link);	/* Alloc a bpstat to
+							   explain stop.  */
 
 	  /* Assume we stop.  Should we find a watchpoint that is not
 	     actually triggered, or if the condition of the breakpoint
@@ -5400,12 +5367,15 @@ bpstat_stop_status (const address_space *aspace,
   if (!target_supports_stopped_by_sw_breakpoint ()
       || !target_supports_stopped_by_hw_breakpoint ())
     {
-      for (ix = 0; VEC_iterate (bp_location_p, moribund_locations, ix, loc); ++ix)
+      bp_location *loc;
+
+      for (int ix = 0;
+	   VEC_iterate (bp_location_p, moribund_locations, ix, loc); ++ix)
 	{
 	  if (breakpoint_location_address_match (loc, aspace, bp_addr)
 	      && need_moribund_for_location_type (loc))
 	    {
-	      bs = new bpstats (loc, &bs_link);
+	      bpstat bs = new bpstats (loc, &bs_link);
 	      /* For hits of moribund locations, we should just proceed.  */
 	      bs->stop = 0;
 	      bs->print = 0;
@@ -5414,6 +5384,33 @@ bpstat_stop_status (const address_space *aspace,
 	}
     }
 
+  return bs_head;
+}
+
+/* See breakpoint.h.  */
+
+bpstat
+bpstat_stop_status (const address_space *aspace,
+		    CORE_ADDR bp_addr, ptid_t ptid,
+		    const struct target_waitstatus *ws,
+		    bpstat stop_chain)
+{
+  struct breakpoint *b = NULL;
+  /* First item of allocated bpstat's.  */
+  bpstat bs_head = stop_chain;
+  bpstat bs;
+  int need_remove_insert;
+  int removed_any;
+
+  /* First, build the bpstat chain with locations that explain a
+     target stop, while being careful to not set the target running,
+     as that may invalidate locations (in particular watchpoint
+     locations are recreated).  Resuming will happen here with
+     breakpoint conditions or watchpoint expressions that include
+     inferior function calls.  */
+  if (bs_head == NULL)
+    bs_head = build_bpstat_chain (aspace, bp_addr, ws);
+
   /* A bit of special processing for shlib breakpoints.  We need to
      process solib loading here, so that the lists of loaded and
      unloaded libraries are correct before we handle "catch load" and

gdb/breakpoint.h

@@ -920,9 +920,37 @@ extern void bpstat_clear (bpstat *);
    is part of the bpstat is copied as well.  */
 extern bpstat bpstat_copy (bpstat);
 
+/* Build the (raw) bpstat chain for the stop information given by ASPACE,
+   BP_ADDR, and WS.  Returns the head of the bpstat chain.  */
+
+extern bpstat build_bpstat_chain (const address_space *aspace,
+				  CORE_ADDR bp_addr,
+				  const struct target_waitstatus *ws);
+
+/* Get a bpstat associated with having just stopped at address
+   BP_ADDR in thread PTID.  STOP_CHAIN may be supplied as a previously
+   computed stop chain or NULL, in which case the stop chain will be
+   computed using build_bpstat_chain.
+
+   Determine whether we stopped at a breakpoint, etc, or whether we
+   don't understand this stop.  Result is a chain of bpstat's such
+   that:
+
+   if we don't understand the stop, the result is a null pointer.
+
+   if we understand why we stopped, the result is not null.
+
+   Each element of the chain refers to a particular breakpoint or
+   watchpoint at which we have stopped.  (We may have stopped for
+   several reasons concurrently.)
+
+   Each element of the chain has valid next, breakpoint_at,
+   commands, FIXME??? fields.  */
+
 extern bpstat bpstat_stop_status (const address_space *aspace,
 				  CORE_ADDR pc, ptid_t ptid,
-				  const struct target_waitstatus *ws);
+				  const struct target_waitstatus *ws,
+				  bpstat stop_chain = NULL);
 
 /* This bpstat_what stuff tells wait_for_inferior what to do with a
    breakpoint (a challenging task).

gdb/infrun.c

@@ -5862,6 +5862,7 @@ handle_signal_stop (struct execution_control_state *ecs)
   ecs->event_thread->control.stop_step = 0;
   stop_print_frame = 1;
   stopped_by_random_signal = 0;
+  bpstat stop_chain = NULL;
 
   /* Hide inlined functions starting here, unless we just performed stepi or
      nexti.  After stepi and nexti, always show the innermost frame (not any
@@ -5893,7 +5894,8 @@ handle_signal_stop (struct execution_control_state *ecs)
 					     ecs->event_thread->prev_pc,
 					     &ecs->ws)))
 	{
-	  skip_inline_frames (ecs->ptid);
+	  stop_chain = build_bpstat_chain (aspace, stop_pc, &ecs->ws);
+	  skip_inline_frames (ecs->ptid, stop_chain);
 
 	  /* Re-fetch current thread's frame in case that invalidated
 	     the frame cache.  */
@@ -5942,7 +5944,7 @@ handle_signal_stop (struct execution_control_state *ecs)
      handles this event.  */
   ecs->event_thread->control.stop_bpstat
     = bpstat_stop_status (get_current_regcache ()->aspace (),
-			  stop_pc, ecs->ptid, &ecs->ws);
+			  stop_pc, ecs->ptid, &ecs->ws, stop_chain);
 
   /* Following in case break condition called a
      function.  */

gdb/inline-frame.c

@@ -18,6 +18,7 @@
    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "defs.h"
+#include "breakpoint.h"
 #include "inline-frame.h"
 #include "addrmap.h"
 #include "block.h"
@@ -284,12 +285,36 @@ block_starting_point_at (CORE_ADDR pc, const struct block *block)
   return 1;
 }
 
-/* Skip all inlined functions whose call sites are at the current PC.
-   Frames for the hidden functions will not appear in the backtrace until the
-   user steps into them.  */
+/* Loop over the stop chain and determine if execution stopped in an
+   inlined frame because of a user breakpoint.  THIS_PC is the current
+   frame's PC.  */
+
+static bool
+stopped_by_user_bp_inline_frame (CORE_ADDR this_pc, bpstat stop_chain)
+{
+  for (bpstat s = stop_chain; s != NULL; s = s->next)
+    {
+      struct breakpoint *bpt = s->breakpoint_at;
+
+      if (bpt != NULL && user_breakpoint_p (bpt))
+	{
+	  bp_location *loc = s->bp_location_at;
+	  enum bp_loc_type t = loc->loc_type;
+
+	  if (loc->address == this_pc
+	      && (t == bp_loc_software_breakpoint
+		  || t == bp_loc_hardware_breakpoint))
+	    return true;
+	}
+    }
+
+  return false;
+}
+
+/* See inline-frame.h.  */
 
 void
-skip_inline_frames (ptid_t ptid)
+skip_inline_frames (ptid_t ptid, bpstat stop_chain)
 {
   const struct block *frame_block, *cur_block;
   struct symbol *last_sym = NULL;
@@ -313,8 +338,14 @@ skip_inline_frames (ptid_t ptid)
 	      if (BLOCK_START (cur_block) == this_pc
 		  || block_starting_point_at (this_pc, cur_block))
 		{
-		  skip_count++;
-		  last_sym = BLOCK_FUNCTION (cur_block);
+		  /* Do not skip the inlined frame if execution
+		     stopped in an inlined frame because of a user
+		     breakpoint.  */
+		  if (!stopped_by_user_bp_inline_frame (this_pc, stop_chain))
+		    {
+		      skip_count++;
+		      last_sym = BLOCK_FUNCTION (cur_block);
+		    }
 		}
 	      else
 		break;

gdb/inline-frame.h

@@ -22,16 +22,21 @@
 
 struct frame_info;
 struct frame_unwind;
+struct bpstats;
 
 /* The inline frame unwinder.  */
 
 extern const struct frame_unwind inline_frame_unwind;
 
 /* Skip all inlined functions whose call sites are at the current PC.
-   Frames for the hidden functions will not appear in the backtrace until the
-   user steps into them.  */
 
-void skip_inline_frames (ptid_t ptid);
+   If non-NULL, STOP_CHAIN is used to determine whether a stop was caused by
+   a user breakpoint.  In that case, do not skip that inlined frame.  This
+   allows the inlined frame to be treated as if it were non-inlined from the
+   user's perspective.  GDB will stop "in" the inlined frame instead of
+   the caller.  */
+
+void skip_inline_frames (ptid_t ptid, struct bpstats *stop_chain);
 
 /* Forget about any hidden inlined functions in PTID, which is new or
    about to be resumed.  If PTID is minus_one_ptid, forget about all

gdb/testsuite/ChangeLog

@@ -1,3 +1,18 @@
+2018-05-17  Keith Seitz  <keiths@redhat.com>
+
+	* gdb.ada/bp_inlined_func.exp: Update inlined frame locations
+	in expected breakpoint stop locations.
+	* gdb.dwarf2/implptr.exp (implptr_test_baz): Use up/down to
+	move to proper scope to test variable values.
+	* gdb.opt/inline-break.c (inline_func1, not_inline_func1)
+	(inline_func2, not_inline_func2, inline_func3, not_inline_func3):
+	New functions.
+	(main): Call not_inline_func3.
+	* gdb.opt/inline-break.exp: Start inferior and set breakpoints at
+	inline_func1, inline_func2, and inline_func3.  Test that when each
+	breakpoint is hit, GDB properly reports both the stop location
+	and the backtrace. Repeat tests for temporary breakpoints.
+
 2018-05-15  Maciej W. Rozycki  <macro@mips.com>
 
 	* gdb.server/server-kill.exp: Verify whether `server_pid' exists

gdb/testsuite/gdb.ada/bp_inlined_func.exp

@@ -38,21 +38,13 @@ gdb_test "break read_small" \
 # We do not verify each breakpoint info, but use continue commands instead
 # to verify that we properly stop on each expected breakpoint.
 
-gdb_test "continue" \
-         "Breakpoint $decimal, b\\.doit \\(\\).*" \
-         "Hitting first call of read_small"
-
-gdb_test "continue" \
-         "Breakpoint $decimal, foo \\(\\).*" \
-         "Hitting second call of read_small"
-
-gdb_test "continue" \
-         "Breakpoint $decimal, c\\.c_doit \\(\\).*" \
-         "Hitting third call of read_small"
-
-gdb_test "continue" \
-         "Breakpoint $decimal, c\\.c_doit2 \\(\\).*" \
-         "Hitting fourth call of read_small"
+for {set i 0} {$i < 4} {incr i} {
+    with_test_prefix "iteration $i" {
+	gdb_test "continue" \
+	    "Breakpoint $decimal, b\\.read_small \\(\\).*" \
+	    "stopped in read_small"
+    }
+}
 
 gdb_test "continue" \
          "Continuing\..*$inferior_exited_re.*" \

gdb/testsuite/gdb.dwarf2/implptr.exp

@@ -66,9 +66,13 @@ proc implptr_test_baz {} {
     gdb_test "break implptr.c:$line" "Breakpoint 3.*" \
 	"set baz breakpoint for implptr"
     gdb_continue_to_breakpoint "continue to baz breakpoint for implptr"
+
+    # We are breaking in an inlined function.  GDB should appear to
+    # have stopped "in" the inlined function.
+    gdb_test "up" "#1  foo .*"
     gdb_test {p p[0].y} " = 92" "sanity check element 0"
     gdb_test {p p[1].y} " = 46" "sanity check element 1"
-    gdb_test "step" "\r\nadd \\(.*" "enter the inlined function"
+    gdb_test "down" "#0  add .*"
     gdb_test "p a->y" " = 92" "check element 0 for the offset"
     gdb_test "p b->y" " = 46" "check element 1 for the offset"
     gdb_continue_to_breakpoint "ignore the second baz breakpoint"