[PING][PATCH] [gdb/testsuite] Fix gdb.base/inline-frame-cycle-unwind.exp for s390x (alternative)

[Tom de Vries <tdevries@suse.de>]

On 12/11/25 2:39 PM, Tom de Vries wrote:
> With test-case gdb.base/inline-frame-cycle-unwind.exp on s390x-linux, I run
> into:
> ...
>   (gdb) bt^M
>   #0  inline_func () at inline-frame-cycle-unwind.c:49^M
>   #1  normal_func () at inline-frame-cycle-unwind.c:32^M
>   #2  0x000000000100065c in inline_func () at inline-frame-cycle-unwind.c:45^M
>   #3  normal_func () at inline-frame-cycle-unwind.c:32^M
>   Backtrace stopped: previous frame identical to this frame (corrupt stack?)^M
>   (gdb) FAIL: $exp: bt: cycle at level 5: backtrace when the unwind is broken \
>     at frame 5
> ...
> 
> In contrast, on x86_64-linux, I get:
> ...
>   (gdb) bt^M
>   #0  inline_func () at inline-frame-cycle-unwind.c:49^M
>   #1  normal_func () at inline-frame-cycle-unwind.c:32^M
>   #2  0x0000000000401157 in inline_func () at inline-frame-cycle-unwind.c:45^M
>   #3  normal_func () at inline-frame-cycle-unwind.c:32^M
>   #4  0x0000000000401157 in inline_func () at inline-frame-cycle-unwind.c:45^M
>   #5  normal_func () at inline-frame-cycle-unwind.c:32^M
>   Backtrace stopped: previous frame identical to this frame (corrupt stack?)^M
>   (gdb) PASS: $exp: bt: cycle at level 5: backtrace when the unwind is broken \
>     at frame 5
> ...
> 
> AFAIU, the mechanism of the test is as follows: the custom unwinder produces the
> frame-id for frame #5 at frame #4.  Consequently, when arriving at frame #5, a
> cycle is detected.
> 
> [ It took me a while to understand this because of the following off-by-one
> confusion: for frame #0, we get pending_frame.level() == 1.  So when
> stop_at_level == 5, the custom unwinder calculates a frame-id for frame #4,
> not frame #5.  But the frame-id it calculates is the one for frame #5, so
> unwinding will stop at frame #5 because the frame-ids for frame #4 and
> frame #5 are identical. ]
> 
> This relies on the test-case to calculate the offending frame-id, and the
> problem on s390x is that that calculation is incorrect.
> 
> Fix this by using "maint print frame-id" to get all frame-ids, and using those
> instead.
> 

Ping.

Thanks,
- Tom

> Tested on x86_64-linux and s390x-linux.
> ---
>   .../gdb.base/inline-frame-cycle-unwind.exp          | 13 +++++++++++++
>   gdb/testsuite/gdb.base/inline-frame-cycle-unwind.py |  8 +++++---
>   2 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/gdb/testsuite/gdb.base/inline-frame-cycle-unwind.exp b/gdb/testsuite/gdb.base/inline-frame-cycle-unwind.exp
> index 7fc47af624f..5c6504323ee 100644
> --- a/gdb/testsuite/gdb.base/inline-frame-cycle-unwind.exp
> +++ b/gdb/testsuite/gdb.base/inline-frame-cycle-unwind.exp
> @@ -72,6 +72,19 @@ gdb_continue_to_breakpoint "stop at test breakpoint"
>   gdb_test_no_output "source ${pyfile}"\
>       "import python scripts"
>   
> +foreach_with_prefix n { 0 1 2 3 4 5 6 } {
> +    set sp 0x0
> +    set pc 0x0
> +    gdb_test_multiple "maint print frame-id $n" "" {
> +	-re -wrap "frame-id for frame #$n: {stack=($hex),code=($hex),.*}" {
> +	    set sp $expect_out(1,string)
> +	    set pc $expect_out(2,string)
> +	    gdb_test_no_output "python frame_id_sp.append($sp)"
> +	    gdb_test_no_output "python frame_id_pc.append($pc)"
> +	}
> +    }
> +}
> +
>   # Test with and without filters.
>   foreach bt_cmd { "bt" "bt -no-filters" } {
>       with_test_prefix "$bt_cmd" {
> diff --git a/gdb/testsuite/gdb.base/inline-frame-cycle-unwind.py b/gdb/testsuite/gdb.base/inline-frame-cycle-unwind.py
> index 55dea989512..25a67b1a7c9 100644
> --- a/gdb/testsuite/gdb.base/inline-frame-cycle-unwind.py
> +++ b/gdb/testsuite/gdb.base/inline-frame-cycle-unwind.py
> @@ -26,6 +26,9 @@ stop_at_level = None
>   # function called recursively.
>   stack_adjust = None
>   
> +frame_id_sp = []
> +frame_id_pc = []
> +
>   
>   class FrameId(object):
>       def __init__(self, sp, pc):
> @@ -55,9 +58,8 @@ class TestUnwinder(Unwinder):
>           if stop_at_level not in [1, 3, 5]:
>               raise gdb.GdbError("invalid stop_at_level")
>   
> -        sp_desc = pending_frame.architecture().registers().find("sp")
> -        sp = pending_frame.read_register(sp_desc) + stack_adjust
> -        pc = (gdb.lookup_symbol("normal_func"))[0].value().address
> +        sp = frame_id_sp[stop_at_level]
> +        pc = frame_id_pc[stop_at_level]
>           unwinder = pending_frame.create_unwind_info(FrameId(sp, pc))
>   
>           for reg in pending_frame.architecture().registers("general"):
> 
> base-commit: 2271dee682787051c0628c869d7cdb220bdd0e67