Re: [pushed] [gdb/testsuite] Use maint ignore-probes in gdb.base/longjmp.exp

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

On 2/9/23 12:58, Luis Machado wrote:
> On 2/9/23 10:37, Luis Machado via Gdb-patches wrote:
>> On 2/8/23 20:36, Tom de Vries wrote:
>>> On 2/8/23 19:06, Luis Machado wrote:
>>>> On 2/8/23 15:38, Tom de Vries wrote:
>>>>> On 2/8/23 15:51, Luis Machado wrote:
>>>>>> On 2/8/23 14:48, Tom de Vries wrote:
>>>>>>> On 2/8/23 14:27, Luis Machado wrote:
>>>>>>>> Hi Tom,
>>>>>>>>
>>>>>>>> Is the entire test supposed to PASS? I'm seeing the following on 
>>>>>>>> my aarch64/Ubuntu 22.04 setup:
>>>>>>>>
>>>>>>>> FAIL: gdb.base/longjmp.exp: with_probes=0: pattern 2: next over 
>>>>>>>> call_longjmp (the program is no longer running)
>>>>>>>> FAIL: gdb.base/longjmp.exp: with_probes=0: pattern 2: next over 
>>>>>>>> setjmp (the program is no longer running)
>>>>>>>> FAIL: gdb.base/longjmp.exp: with_probes=0: pattern 2: setup: 
>>>>>>>> breakpoint at pattern start (got interactive prompt)
>>>>>>>> FAIL: gdb.base/longjmp.exp: with_probes=0: pattern 2: setup: 
>>>>>>>> breakpoint at safety net (got interactive prompt)
>>>>>>>> FAIL: gdb.base/longjmp.exp: with_probes=0: pattern 2: setup: 
>>>>>>>> continue to breakpoint at pattern start (the program exited)
>>>>>>>> FAIL: gdb.base/longjmp.exp: with_probes=0: pattern 3: next over 
>>>>>>>> pattern (the program is no longer running)
>>>>>>>> FAIL: gdb.base/longjmp.exp: with_probes=0: pattern 3: setup: 
>>>>>>>> breakpoint at pattern start (got interactive prompt)
>>>>>>>> FAIL: gdb.base/longjmp.exp: with_probes=0: pattern 3: setup: 
>>>>>>>> continue to breakpoint at pattern start (the program is no 
>>>>>>>> longer running)
>>>>>>>>
>>>>>>>> Maybe something is genuinely broken for aarch64 though, or I'm 
>>>>>>>> missing some packages/debuginfo.
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> I just ran this test-case on openSUSE Leap 15.4 aarch64, no 
>>>>>>> problems found.
>>>>>>>
>>>>>>
>>>>>> Alright. That's good to know.
>>>>>
>>>>> FWIW, I've tried this test-case also on various x86_64 distros 
>>>>> other than the usual openSUSE Leap 15.4: ubuntu 20.04, fedora 37 
>>>>> and opensuse tumbleweed, again no problems found.
>>>>
>>>> I did a brief investigation on this one, and gdb seems to be doing 
>>>> something strange.
>>>>
>>>> For Ubuntu 20.04 we have the following, just after deleting the 
>>>> breakpoints leading into the pattern 2 check:
>>>>
>>>>
>>>> (gdb) info source
>>>> Current source file is longjmp.c
>>>> Compilation directory is /build/glibc-RIFKjK/glibc-2.31/setjmp
>>>> Located in /repos/binutils-gdb/gdb/testsuite/gdb.base/longjmp.c
>>>> Contains 82 lines.
>>>> Source language is c.
>>>> Producer is GNU C11 9.4.0 -moutline-atomics -mlittle-endian 
>>>> -mabi=lp64 -g -O2 -std=gnu11 -fgnu89-inline -fmerge-all-constants 
>>>> -frounding-math
>>>>   -fstack-protector-strong -fmath-errno -fPIC 
>>>> -ftls-model=initial-exec -fasynchronous-unwind-tables 
>>>> -fstack-protector-strong -fstack-clash-pro
>>>> tection.
>>>> Compiled with DWARF 4 debugging format.
>>>> Does not include preprocessor macro info.
>>>> (gdb) b 69
>>>> Breakpoint 4 at 0xaaaaaaaa08ec: file 
>>>> /builds/binutils-gdb-arm64-focal/gdb/testsuite/../../../../repos/binutils-gdb/gdb/tes
>>>> tsuite/gdb.base/longjmp.c, line 69.
>>>> (gdb)
>>>>
>>>> And for Ubuntu 22.04:
>>>>
>>>> (gdb) info source
>>>> Current source file is ./setjmp/longjmp.c
>>>> Compilation directory is ./setjmp
>>>> Located in /repos/binutils-gdb/gdb/testsuite/gdb.base/longjmp.c
>>>> Contains 82 lines.
>>>> Source language is c.
>>>> Producer is GNU C11 11.2.0 -mlittle-endian -mabi=lp64 -g -O2 
>>>> -std=gnu11 -fgnu89-inline -fmerge-all-constants -frounding-math 
>>>> -fstack-protecto
>>>> r-strong -fno-common -fmath-errno -fPIC -ftls-model=initial-exec 
>>>> -fasynchronous-unwind-tables -fstack-protector-strong 
>>>> -fstack-clash-protecti
>>>> on.
>>>> Compiled with DWARF 5 debugging format.
>>>> Does not include preprocessor macro info.
>>>> (gdb) b 69
>>>> No line 69 in the current file.
>>>> Make breakpoint pending on future shared library load? (y or [n]) n
>>>> (gdb)
>>>>
>>>> There is a small difference in debug info (dwarf 4 for 20.04 and 
>>>> dwarf 5 for 22.04), source file name and compilation directory.
>>>>
>>>> What is strange is that gdb's 'info source' output seems to refer to 
>>>> the glibc longjmp source file as the current one. And the 
>>>> compilation directory
>>>> is also glibc's. The "Located in" field is from the testcase source, 
>>>> also named longjmp.c. The "Contains" line is also based on the 
>>>> testcase source file.
>>>>
>>>> Investigating further, if you "list", it will output the sources 
>>>> from the testcase file as well.
>>>>
>>>> Finally, for 20.04, the "break" command will use the testcase source 
>>>> file, but in 22.04 it will use the glibc source file. I'm guessing 
>>>> the fact that glibc's
>>>> source file in 20.04 is also called longjmp.c makes it work somehow. 
>>>> But in 22.04 the glibc source file is now ./setjmp/longjmp.c, and I 
>>>> guess gdb now
>>>> attempts to insert a breakpoint in the glibc source file, which 
>>>> doesn't have line 63. So it all goes downhill from there.
>>>>
>>>> I'm not sure if this is a long-standing bug or if it is a somewhat 
>>>> recent regression. But gdb seems to be genuinely confused about 
>>>> which source file is the current one
>>>> and which one to use for various commands.
>>>>
>>>> I'd expect gdb to pick one and stick with it, but it doesn't seem to 
>>>> be the case.
>>>>
>>>> Maybe we just uncovered a new bug with source handling.
>>>
>>> I suspect the FAILs will disappear if we replace "break <n>" with 
>>> "break $srcfile:<n>".  I'm not sure yet whether this is a fix or a 
>>> workaround.
>>
>> I suppose. But it seems there is a different underlying issue of gdb 
>> getting confused about what is the current source file.
>>
>>>
>>> Please file a PR and attach the entire gdb.log, I want to take a look 
>>> at it.
>>
>> Will do.
> 
> Looking around I found 
> https://sourceware.org/bugzilla/show_bug.cgi?id=19474, which seems to 
> indicate some confusing cases aren't really a bug.

Does that mean you're not planning to post the gdb.log?

Thanks,
- Tom