[PATCH] Fix backtrace limit stopping on inline frame

[Hannes Domani <ssbssa@yahoo.de>]

If you have set up a backtrace limit, and the backtrace stops
because of this in an inline frame with arguments, you get an
assertion failure:
```
(gdb) bt
#0  normal_frame (i=0) at gdb-29865.c:4
#1  0x000000013fe3162a in inline_frame (i=0) at gdb-29865.c:9
#2  main () at gdb-29865.c:14
(gdb) set backtrace limit 2
(gdb) bt
#0  normal_frame (i=0) at gdb-29865.c:4
#1  0x000000013fe3162a in inline_frame (
C:/src/repos/binutils-gdb.git/gdb/frame.c:3346: internal-error: reinflate: Assertion `m_cached_level >= -1' failed.
```

And if this one if fixed, there is another one as well:
```
(gdb) bt
#0  normal_frame (i=0) at gdb-29865.c:4
#1  0x000000013fdf162a in inline_frame (
C:/src/repos/binutils-gdb.git/gdb/dwarf2/loc.c:1160: internal-error: dwarf_expr_reg_to_entry_parameter: Assertion `frame != NULL' failed.
```

The reason for both of them is this kind of loop:
```
  while (get_frame_type (frame) == INLINE_FRAME)
    frame = get_prev_frame (frame);
```
Since get_prev_frame respects the backtrace limit, it will return
NULL, and from there on you can't continue.
This changes these loops to use get_prev_frame_always instead, so
you always get a non-inline frame in the end.

With this backtrace works:
```
(gdb) bt
#0  normal_frame (i=0) at gdb-29865.c:4
#1  0x000000013fd4162a in inline_frame (i=0) at gdb-29865.c:9
(gdb)
```

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=29865
---
 gdb/dwarf2/frame.c                  | 2 +-
 gdb/dwarf2/loc.c                    | 2 +-
 gdb/testsuite/gdb.opt/inline-bt.c   | 8 ++++----
 gdb/testsuite/gdb.opt/inline-bt.exp | 1 +
 4 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c
index d3d1ecdf1f5..143b934e5ef 100644
--- a/gdb/dwarf2/frame.c
+++ b/gdb/dwarf2/frame.c
@@ -1423,7 +1423,7 @@ dwarf2_frame_cfa (frame_info_ptr this_frame)
 		 _("cfa not available for record btrace target"));
 
   while (get_frame_type (this_frame) == INLINE_FRAME)
-    this_frame = get_prev_frame (this_frame);
+    this_frame = get_prev_frame_always (this_frame);
   if (get_frame_unwind_stop_reason (this_frame) == UNWIND_UNAVAILABLE)
     throw_error (NOT_AVAILABLE_ERROR,
 		_("can't compute CFA for this frame: "
diff --git a/gdb/dwarf2/loc.c b/gdb/dwarf2/loc.c
index c15221eb7a2..b1f188bf9c5 100644
--- a/gdb/dwarf2/loc.c
+++ b/gdb/dwarf2/loc.c
@@ -1156,7 +1156,7 @@ dwarf_expr_reg_to_entry_parameter (frame_info_ptr frame,
 
   while (get_frame_type (frame) == INLINE_FRAME)
     {
-      frame = get_prev_frame (frame);
+      frame = get_prev_frame_always (frame);
       gdb_assert (frame != NULL);
     }
 
diff --git a/gdb/testsuite/gdb.opt/inline-bt.c b/gdb/testsuite/gdb.opt/inline-bt.c
index 8dac8d30300..0dad0f47e6e 100644
--- a/gdb/testsuite/gdb.opt/inline-bt.c
+++ b/gdb/testsuite/gdb.opt/inline-bt.c
@@ -28,15 +28,15 @@ volatile int result;
 
 void bar(void);
 
-inline ATTR int func1(void)
+inline ATTR int func1(int s)
 {
   bar ();
-  return x * y;
+  return x * y + s;
 }
 
 inline ATTR int func2(void)
 {
-  return x * func1 ();
+  return x * func1 (1);
 }
 
 int main (void)
@@ -47,7 +47,7 @@ int main (void)
   y = 8;
   bar ();
 
-  val = func1 ();
+  val = func1 (2);
   result = val;
 
   val = func2 ();
diff --git a/gdb/testsuite/gdb.opt/inline-bt.exp b/gdb/testsuite/gdb.opt/inline-bt.exp
index 501b24109e3..b0e5f61a5c7 100644
--- a/gdb/testsuite/gdb.opt/inline-bt.exp
+++ b/gdb/testsuite/gdb.opt/inline-bt.exp
@@ -65,3 +65,4 @@ gdb_test "up" "#1  .*func1.*" "up from bar (4)"
 gdb_test "info frame" ".*in func1.*" "info frame still works"
 # Verify the user visible limit works as expected.
 gdb_test "up" "Initial frame selected; you cannot go up." "up hits limit"
+gdb_test "backtrace" "#0  bar.*#1  .*func1.*" "backtrace hits limit"
-- 
2.35.1