Re: [PATCH] Fix backtrace limit stopping on inline frame

[Andrew Burgess <aburgess@redhat.com>]

Hannes Domani <ssbssa@yahoo.de> writes:

> 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:

s/one if fixed/one is fixed/.

Otherwise, looks good.  Thanks for fixing this.

Approved-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew


> ```
> (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