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

[Luis Machado <luis.machado@arm.com>]

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.

> 
>>
>> Thanks,
>> - Tom
>