[PATCH] Fix inline frame unwinding breakage

[Tom de Vries]

On 23-04-2020 19:51, Luis Machado via Gdb-patches wrote:
> On 4/22/20 8:22 AM, Luis Machado wrote:
>> Hi Andrew,
>>
>> On 4/22/20 6:37 AM, Andrew Burgess wrote:
>>> * Luis Machado via Gdb-patches <gdb-patches@sourceware.org>
>>> [2020-04-14 18:38:36 -0300]:
>>>
>>>> *** re-sending due to the poor choice of characters for the backtrace
>>>> annotations. GIT swallowed parts of it.
>>>>
>>>> There has been some breakage for aarch64-linux, arm-linux and
>>>> s390-linux in
>>>> terms of inline frame unwinding. There may be other targets, but
>>>> these are
>>>> the ones i'm aware of.
>>>>
>>>> The following testcases started to show numerous failures and
>>>> trigger internal
>>>> errors in GDB after commit 1009d92fc621bc4d017029b90a5bfab16e17fde5,
>>>> "Find tailcall frames before inline frames".
>>>>
>>>> gdb.opt/inline-break.exp
>>>> gdb.opt/inline-cmds.exp
>>>> gdb.python/py-frame-inline.exp
>>>> gdb.reverse/insn-reverse.exp
>>>>
>>>> The internal errors were of this kind:
>>>>
>>>> binutils-gdb/gdb/frame.c:579: internal-error: frame_id
>>>> get_frame_id(frame_info*): Assertion `fi->level == 0' failed.
>>>
>>> I have also started seeing this assert on RISC-V, and your patch
>>> resolves this issue for me, so I'm keen to see this merged.
>>
>> Great.
>>
>>>
>>> I took a look through and it all looks good to me - is there anything
>>> holding this back from being merged?
>>
>> Not really. I was waiting for an OK before pushing it.
>>
>>>
>>> Thanks,
>>> Andrew
> 
> I've pushed this now. Tromey and Andrew OK-ed it on IRC.

This causes at least:
...
FAIL: gdb.arch/amd64-entry-value.exp: tailcall: bt
FAIL: gdb.arch/amd64-entry-value.exp: tailcall: p i
FAIL: gdb.arch/amd64-entry-value.exp: tailcall: p i@entry
FAIL: gdb.arch/amd64-entry-value.exp: tailcall: p j
FAIL: gdb.arch/amd64-entry-value.exp: tailcall: p j@entry
FAIL: gdb.arch/amd64-entry-value.exp: p $sp0 == $sp
FAIL: gdb.arch/amd64-entry-value.exp: frame 3
FAIL: gdb.arch/amd64-entry-value.exp: down
FAIL: gdb.arch/amd64-entry-value.exp: disassemble
FAIL: gdb.arch/amd64-entry-value.exp: ambiguous: bt
FAIL: gdb.arch/amd64-entry-value.exp: self: bt
FAIL: gdb.arch/amd64-entry-value.exp: self: bt debug entry-values
FAIL: gdb.arch/amd64-tailcall-cxx.exp: bt
FAIL: gdb.arch/amd64-tailcall-noret.exp: bt
FAIL: gdb.arch/amd64-tailcall-self.exp: bt
...

Looking at the first FAIL, before this commit we have:
...
(gdb) PASS: gdb.arch/amd64-entry-value.exp: continue to breakpoint:
tailcall: breakhere
bt^M
#0  d (i=71, i@entry=70, j=73.5, j@entry=72.5) at
gdb.arch/amd64-entry-value.cc:34^M
#1  0x00000000004006af in c (i=i@entry=7, j=j@entry=7.25) at
gdb.arch/amd64-entry-value.cc:47^M
#2  0x00000000004006cd in b (i=i@entry=5, j=j@entry=5.25) at
gdb.arch/amd64-entry-value.cc:59^M
#3  0x0000000000400524 in main () at gdb.arch/amd64-entry-value.cc:229^M
(gdb) PASS: gdb.arch/amd64-entry-value.exp: tailcall: bt
...
which has now degraded into:
...
(gdb) PASS: gdb.arch/amd64-entry-value.exp: continue to breakpoint:
tailcall: breakhere
bt^M
#0  d (i=<optimized out>, j=<optimized out>) at
gdb.arch/amd64-entry-value.cc:34^M
#1  0x0000000000400524 in main () at gdb.arch/amd64-entry-value.cc:229^M
(gdb) FAIL: gdb.arch/amd64-entry-value.exp: tailcall: bt
...

Thanks,
- Tom