Re: [lttng-dev] Using lttng-ust 2.13.6 from Yocto Kirkstone and getting weird segfault saying strlen_asimd.S can't be found.

Hi Brian,

On 7/30/24 11:54 AM, Brian Hutchinson wrote:
> Hi Kienan,
> 
> I noticed looking thru the 38k line LTTNG_UST_DEBUG session this line:
> 
> "       810:     /usr/lib/liblttng-ust.so.1: error: symbol lookup
> error: undefined symbol: ltt_probe_register (fatal)"
>  > ... and it jogged my memory that I did see some abi conflict messages
> in lttng-ust "make check" that I don't know if they are "good" or
> "bad" but could be related???
> 

This is how lttng-ust.so.1 checks for lttng-ust.so.0 in the same 
process. It's normal.

C.f. 
https://github.com/lttng/lttng-ust/blob/5db855839d4526cb2b80c45096884b7f6136da9f/src/lib/lttng-ust/lttng-ust-comm.c#L2221

> Anyway, attaching a tar of lttng-ust and lttng-tools "make check" for
> your enjoyment.
> 
> Regards,
> 
> Brian
> 
> 
> 
> 
> On Tue, Jul 30, 2024 at 8:40 AM Brian Hutchinson <[email protected]> wrote:
>>
>> On Mon, Jul 29, 2024 at 3:03 PM Kienan Stewart <[email protected]> wrote:
>>>
>>> Hi Brian,
>>>
>>> On 7/25/24 3:54 PM, Brian Hutchinson wrote:
>>>> Hi Kienan,
>>>>
>>>> I'll answer your questions below, but I've got questions on what I saw
>>>> building and installing lttng-tools (2.13.13) and lttng-ust (2.13.8).
>>>>
>>>> Based on the struggles I've had trying to get lttng to work with my
>>>> app over various Yocto versions (Dunfell & Kirkstone) and lttng
>>>> version, I think the problems I'm facing are mostly around C++ and
>>>> weak and hidden symbols in Yocto toolchain.
>>>>
>>>> When I started my app with the options you mentioned previously a
>>>> while back, Id see things like:
>>>>
>>>> # LTTNG_UST_DEBUG=1 LTTNG_UST_REGISTER_TIMEOUT=-1 /opt/tc/TrafficController
>>>> liblttng_ust_tracepoint[4012/4012]: Your compiler treats weak symbols
>>>> with hidden visibility for integer objects as SAME address between
>>>> compile units part of the same module. (in check_weak_hidden() at
>>>> tracepoint.c:1012)
>>>> liblttng_ust_tracepoint[4012/4012]: Your compiler treats weak symbols
>>>> with hidden visibility for pointer objects as SAME address between
>>>> compile units part of the same module. (in check_weak_hidden() at
>>>> tracepoint.c:1016)
>>>> liblttng_ust_tracepoint[4012/4012]: Your compiler treats weak symbols
>>>> with hidden visibility for 24-byte structure objects as SAME address
>>>> between compile units part of the same module. (in check_weak_hidden()
>>>> at tracepoint.c:1020)
>>>>
>>>
>>> These messages are extra information for debugging and not indicative of
>>> a problem in of itself. C.f.
>>> https://github.com/lttng/lttng-ust/blob/24f7193c9b918bf714a40e9fc908eeb4978ada1c/src/lib/lttng-ust-tracepoint/tracepoint.c#L1010
>>>
>>> There is a unit test related to this:
>>> https://github.com/lttng/lttng-ust/blob/24f7193c9b918bf714a40e9fc908eeb4978ada1c/tests/unit/gcc-weak-hidden/main.c#L76
>>>
>>>
>>>> I further researched this whole 'weak symbol' and 'hidden visibility'
>>>> topic in the lttng-dev archives and it smells a lot like what I've
>>>> been seeing.  You should be able to mix both tracef and tracepoint
>>>> calls in souce code ... but I could not.  I could get a tracef call to
>>>> work but if I put a tracepoint call in the same code then nothing
>>>> would work.  This was with Dunfell 3.1.7 and earlier versions of
>>>> lttng.
>>>>
>>>> At one point I could get a tracepoint call to work but I'd have to let
>>>> our cmake build system build and link the tpp.c file and then turn
>>>> around and use gcc to recompile it and copy it to where all the
>>>> objects were to create the huge .a library the app was built against.
>>>> That's when I first learned there are issues with C++.  I think g++ is
>>>> used to build even .c files that aren't c++.
>>>>
>>>> Then if I tried to put a tracepoint in another sub project, none of
>>>> the tracepoints would work and I'd get empty traces.  This is a
>>>> symptom of the 'weak symbols with hidden visibility' issue ... and I
>>>> finally found others that were having same issue in the archives.  I
>>>> don't fully understand the issues here, although I do understand some
>>>> of what's going on ... I just don't know what to do about it.
>>>>
>>>
>>> You said initially said that you're using `lttng_ust_tracepoint` exactly
>>> as the hello world from the documentation; however, you have just
>>> described several attempts at doing different things. Which case are we
>>> trying to understand here?
>>
>> lttng_ust_tracepoint.  I only mentioned prior tests for context to
>> similar struggles from a year or more ago.
>>
>>
>>>
>>>> At this point I was being encouraged to keep upgrading to newer
>>>> versions of lttng.  Our app never changed, gcc & lttng etc., kept
>>>> changing.  Now with newer versions nothing runs, all I get is an
>>>> immediate segfault.  Again, I'm building just like I did before a year
>>>> or so ago with older versions of Yocto and lttng.  I say all of that
>>>> to give perspective and history of what I've seen and experienced.
>>>> Now this TLS thing has entered the picture too and so far I've only
>>>> changed lttng, I don't know if I should be applying patches to my gcc
>>>> for that issue.  Like I said, I'm currently using Yocto Kirkstone
>>>> 4.0.18 and 6.1.38 kernel.
>>>>
>>>> Now I'll move into the area of things I've seen building/installing
>>>> lttng-tools and lttng-ust natively on the target environment I've
>>>> setup where I can run 'make check' etc.  These are in the category of
>>>> "hey, is this ok, should I be worried about this":
>>>>
>>>> While building lttng-tools I see things like:
>>>>
>>>> *** Warning: Linking the executable userspace-probe-elf-binary against
>>>> the loadable module
>>>> *** libfoo.so is not portable!
>>>>
>>>
>>> The library is for a test program. My understanding is that the library
>>> is compiled that way to force a stripped shared object to be produced in
>>> order to validate that symbol lookups in libraries with no symtab
>>> function as expected by using the dynsym table.
>>>
>>> C.f.
>>> https://github.com/lttng/lttng-tools/commit/ef3dfe5d31c88fb548189a6441aaf8b2afc0bd4b
>>>
>>>> In file included from ../../../src/common/macros.h:15,
>>>>                   from ../../../include/lttng/health-internal.h:19,
>>>>                   from lttng-ctl-health.c:19:
>>>> In function 'lttng_strnlen',
>>>>      inlined from 'lttng_strncpy' at ../../../src/common/macros.h:128:6,
>>>>      inlined from 'set_health_socket_path' at lttng-ctl-health.c:146:9,
>>>>      inlined from 'lttng_health_query' at lttng-ctl-health.c:264:8:
>>>> ../../../src/common/compat/string.h:19:16: warning: 'strnlen'
>>>> specified bound 4096 may exceed source size 37 [-Wstringop-overread]
>>>>     19 |         return strnlen(str, max);
>>>>        |                ^~~~~~~~~~~~~~~~~
>>>> lttng-ctl-health.c: At top level:
>>>> cc1: note: unrecognized command-line option
>>>> '-Wno-incomplete-setjmp-declaration' may have been intended to silence
>>>> earlier diagnostics
>>>
>>> This warning is addressed in
>>> https://github.com/lttng/lttng-tools/commit/b25a59916106e5055be516f61f183a48f459b0b3
>>>
>>>> ** Warning: Linking the shared library libbar.la against the loadable module
>>>> *** libzzz.so is not portable!
>>>>
>>>> *** Warning: Linking the shared library libfoo.la against the loadable module
>>>> *** libbar.so is not portable!
>>>>
>>>> While installing lttng-tools I see things like this:
>>>>
>>>> make[4]: Entering directory '/opt/lttng/lttng-tools-2.13.13/src/lib/lttng-ctl'
>>>>    CC       lttng-ctl.lo
>>>>    CC       snapshot.lo
>>>>    CC       lttng-ctl-health.lo
>>>> In file included from ../../../src/common/macros.h:15,
>>>>                   from ../../../include/lttng/health-internal.h:19,
>>>>                   from lttng-ctl-health.c:19:
>>>> In function 'lttng_strnlen',
>>>>      inlined from 'lttng_strncpy' at ../../../src/common/macros.h:128:6,
>>>>      inlined from 'set_health_socket_path' at lttng-ctl-health.c:146:9,
>>>>      inlined from 'lttng_health_query' at lttng-ctl-health.c:264:8:
>>>> ../../../src/common/compat/string.h:19:16: warning: 'strnlen'
>>>> specified bound 4096 may exceed source size 37 [-Wstringop-overread]
>>>>     19 |         return strnlen(str, max);
>>>>        |                ^~~~~~~~~~~~~~~~~
>>>> lttng-ctl-health.c: At top level:
>>>> cc1: note: unrecognized command-line option
>>>> '-Wno-incomplete-setjmp-declaration' may have been intended to silence
>>>> earlier diagnostics
>>>>
>>>> Making install in trigger-condition-event-matches
>>>> make[2]: Entering directory
>>>> '/opt/lttng/lttng-tools-2.13.13/doc/examples/trigger-condition-event-matches'
>>>>    CC       instrumented-app.o
>>>>    CC       tracepoint-trigger-example.o
>>>>    AR       libtracepoint-trigger-example.a
>>>> ar: `u' modifier ignored since `D' is the default (see `U')
>>>>
>>>> While building lttng-ust I see things like:
>>>>
>>>> Making all in utils
>>>> make[2]: Entering directory
>>>> '/home/iadmin/lttng-ust/lttng-ust-2.13.8/tests/utils'
>>>>    CC       tap.o
>>>>    AR       libtap.a
>>>> ar: `u' modifier ignored since `D' is the default (see `U')
>>>>
>>>
>>> While libtool now uses `cr` by default, automake still defines the
>>> default to `cru` which is what ends up getting used in the example.
>>> Since many distros have changed the configuration of ar such that 'D' is
>>> the default rather than the previous behaviour 'U', 'u' is redundant.
>>>
>>> The behaviour in automake has been changed in automake 1.16.90+.
>>>
>>> C.f.
>>> https://github.com/autotools-mirror/libtool/commit/418129bc63afc312701e84cb8afa5ca413df1ab5
>>>
>>> C.f.
>>> http://git.savannah.gnu.org/cgit/automake.git/commit/?id=8cdbdda5aec652c356fe6dbba96810202176ae75
>>>
>>>> *** Warning: Linking the shared library libzero.la against the
>>>> loadable module
>>>> *** libfakeust0.so is not portable!
>>>>    CCLD     app_noust_indirect_abi0
>>>>
>>>> *** Warning: Linking the executable app_noust_indirect_abi0 against
>>>> the loadable module
>>>> *** libzero.so is not portable!
>>>>    CC       app_noust_indirect_abi0_abi1-app_noust.o
>>>>    CC       libone.lo
>>>>    CCLD     libone.la
>>>>    CCLD     app_noust_indirect_abi0_abi1
>>>>
>>>> *** Warning: Linking the executable app_noust_indirect_abi0_abi1
>>>> against the loadable module
>>>> *** libzero.so is not portable!
>>>>
>>>> *** Warning: Linking the executable app_noust_indirect_abi0_abi1
>>>> against the loadable module
>>>> *** libone.so is not portable!
>>>>    CC       app_noust_indirect_abi1-app_noust.o
>>>>    CCLD     app_noust_indirect_abi1
>>>>
>>>> *** Warning: Linking the executable app_noust_indirect_abi0_abi1
>>>> against the loadable module
>>>> *** libone.so is not portable!
>>>>    CC       app_noust_indirect_abi1-app_noust.o
>>>>    CCLD     app_noust_indirect_abi1
>>>>
>>>> *** Warning: Linking the executable app_noust_indirect_abi1 against
>>>> the loadable module
>>>> *** libone.so is not portable!
>>>>    CC       app_ust.o
>>>>    CC       tp.o
>>>>    CCLD     app_ust
>>>>    CC       app_ust_dlopen.o
>>>>    CCLD     app_ust_dlopen
>>>>    CC       app_ust_indirect_abi0-app_ust.o
>>>>    CC       app_ust_indirect_abi0-tp.o
>>>>    CCLD     app_ust_indirect_abi0
>>>>
>>>> *** Warning: Linking the executable app_ust_indirect_abi0 against the
>>>> loadable module
>>>> *** libzero.so is not portable!
>>>>    CC       app_ust_indirect_abi0_abi1-app_ust.o
>>>>    CC       app_ust_indirect_abi0_abi1-tp.o
>>>>    CCLD     app_ust_indirect_abi0_abi1
>>>>
>>>> *** Warning: Linking the executable app_ust_indirect_abi0_abi1 against
>>>> the loadable module
>>>> *** libzero.so is not portable!
>>>>
>>>> I don't know if these are ok or if I should be worried about any of that.
>>>>
>>>
>>> These are all for different tests.
>>>
>>>> ... now on to your questions below.
>>>>
>>>>
>>>>
>>>> On Wed, Jul 24, 2024 at 12:04 PM Kienan Stewart <[email protected]> wrote:
>>>>>
>>>>> Hi Brian,
>>>>>
>>>>> On 7/22/24 6:00 PM, Brian Hutchinson wrote:
>>>>>> Hi Kienan,
>>>>>>
>>>>>> Took a while to gather your grocery list but I think I have most of it
>>>>>> below ;)
>>>>>
>>>>> thanks for all the extra info. Replies inline below, but I'll cut a lot
>>>>> of the long output for readability.
>>>>>
>>>>> tl;dr the environment continues to be weird, but my present suspicion is
>>>>> that something in either compilation, the linking of your app (eg. with
>>>>> ld when producing the executable), or some post linking stripping might
>>>>> be causing issues.
>>>>
>>>> I'm not aware of any stripping that's going on.  In fact everything is
>>>> being built with debug symbols at the moment and I even turned off
>>>> optimization ... even used the debug friendly -O flag to see if that
>>>> made a difference.
>>>>
>>>>>
>>>>> I will stop digging into further hypotheticals on my side as there is no
>>>>> reproducer for both the environment and the application. If you ever end
>>>>> up with a minimal reproducer that you can share, I'd be more than happy
>>>>> to examine it.
>>>>
>>>> I'm planning on trying to make a small reproducer I can share but not there yet.
>>>>
>>>
>>> Great! I appreciate that you're taking the time to do so.
>>>
>>>>>
>>>>>>
>>>>>> I may have not been clear.  Most of the application components are
>>>>>> statically linked but I think there are some that are built as shared
>>>>>> objects (.so's) so that's what I was referring to.  I know that
>>>>>> lttng-ust is dynamically linked ... I think the lttng-ust docs say this
>>>>>> is only option but also makes reference to the fact static linking was
>>>>>> once possible (in some versions of the documentation) but not supported
>>>>>> anymore (I probably have the docs memorized by now ha, ha ... I've
>>>>>> looked at many, many versions of them).
>>>>>>
>>>>>> Just for full disclosure my ldd looks like:
>>>>>>
>>>>>>           linux-vdso.so.1 (0x0000ffffab196000)
>>>>>>           libfcgi.so.0 => /usr/lib/libfcgi.so.0 (0x0000ffffa57f0000)
>>>>>>           liblttng-ust.so.1 => /usr/lib/liblttng-ust.so.1
>>>>>> (0x0000ffffa5750000)
>>>>>>           libxml2.so.2 => /usr/lib/libxml2.so.2 (0x0000ffffa55d0000)
>>>>>>           librt.so.1 => /lib/librt.so.1 (0x0000ffffa55b0000)
>>>>>>           libm.so.6 => /lib/libm.so.6 (0x0000ffffa5510000)
>>>>>>           libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x0000ffffa52f0000)
>>>>>>           libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x0000ffffa52c0000)
>>>>>>           libc.so.6 => /lib/libc.so.6 (0x0000ffffa5110000)
>>>>>>           /lib/ld-linux-aarch64.so.1 (0x0000ffffab15d000)
>>>>>>           liblttng-ust-common.so.1 =>
>>>>>> /usr/local/lib/liblttng-ust-common.so.1 (0x0000ffffa50e0000)
>>>>>>           liblttng-ust-tracepoint.so.1 =>
>>>>>> /usr/local/lib/liblttng-ust-tracepoint.so.1 (0x0000ffffa50a0000)
>>>>>>           libpthread.so.0 => /lib/libpthread.so.0 (0x0000ffffa5080000)
>>>>>>           libz.so.1 => /lib/libz.so.1 (0x0000ffffa5050000)
>>>>>>
>>>>>>
>>>>>
>>>>> I find it very suspicious that `liblttng-ust.so.1` is in `/usr/lib`,
>>>>> while the other lttng-ust libraries are being loaded from `/usr/local/lib`.
>>>>
>>>> So Yocto puts all of the lttng libs into /usr/lib.  When I sent the
>>>> previous info I was using lttng-tools and modules built by Yocto/OE
>>>> and I setup a native build environment on the target so I could run
>>>> 'make check' etc., and that's why there were things in /usr/local/lib
>>>> because that's where you guys want stuff to be.  So I actually left
>>>> the lttng-ust installables in /usr/local/build but also copied them to
>>>> /usr/lib to overwrite old Yocto versions there.
>>>>
>>>
>>> It's not so much that it's "where we want it to be". The documentation
>>> uses `/usr/local/lib` because `/usr/local` is meant for software
>>> installed by the sysadmin administrator, as is the case when building a
>>> custom version. `/usr/lib` should be used by packages shipped with the
>>> system.
>>>
>>> C.f. https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch04s09.html
>>>
>>> You're free to do as you see fit, but when you start mixing and matching
>>> libraries and some are put in /usr/lib by your system packages and some
>>> you move there manually I find it more difficult to follow what is going on.
>>>
>>>>>
>>>>> This information also matches the statedump and the LD_DEBUG info from
>>>>> later on.
>>>>>
>>>>> Could you verify some of the following information:
>>>>>
>>>>> 1. In your build root for lttng-ust, enumerate all the liblttng*so
>>>>> files. For each shared object, run `file $libname` and record the value
>>>>> of the BuildID hash.R5jow
>>>>
>>>> Sorry, I'm not following you here.  The only buildID hash I can think
>>>> of is with 'eu-unstrip -n' but that's on core files, not individual
>>>> libs.  And looking at the options I have for 'file' on my target, I
>>>> don't see anything that looks like what you are asking.
>>>
>>> Perhaps I wasn't clear, the command to run is really just `file`. As a
>>> fuller example:
>>>
>>> ```
>>> $ file ./src/lib/lttng-ust-fork/.libs/liblttng-ust-fork.so.1.0.0
>>> ./src/lib/lttng-ust-fork/.libs/liblttng-ust-fork.so.1.0.0: ELF 64-bit
>>> LSB shared object, x86-64, version 1 (SYSV), dynamically linked,
>>> BuildID[sha1]=b2b4a0fc449cf317e32c23e0bb57ea1ad702b702, with debug_info,
>>> not stripped
>>
>> Ok, feel stupid now.  When I ran the command before, I used short name
>> and didn't do it on the long name and just got back:
>>
>> # file /usr/lib/liblttng-ust.so
>> /usr/lib/liblttng-ust.so: symbolic link to liblttng-ust.so.1.0.0
>>
>> ... and immediately looked at man page to try to figure out what
>> switch showed BuildID etc., ha, ha.
>>
>> When I do it on long name here is what I see:
>>
>> # file /usr/lib/liblttng-ust-common.so.1.0.0
>> /usr/lib/liblttng-ust-common.so.1.0.0: ELF 64-bit LSB shared object,
>> ARM aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=a50c9a77163b6b91e1f84e57d167c7b77ae707a3, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust-ctl.so.5.0.0
>> /usr/lib/liblttng-ust-ctl.so.5.0.0: ELF 64-bit LSB shared object, ARM
>> aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=547cccac08721ed1c9a7f3c7ebf1de84ddba7fba, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust-cyg-profile-fast.so.1.0.0
>> /usr/lib/liblttng-ust-cyg-profile-fast.so.1.0.0: ELF 64-bit LSB shared
>> object, ARM aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=ad5f71ef5e83ab9a972488976c47db265d3360b9, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust-cyg-profile.so.1.0.0
>> /usr/lib/liblttng-ust-cyg-profile.so.1.0.0: ELF 64-bit LSB shared
>> object, ARM aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=c2c246c1973bd3241aa4f7229fcbcb27ebe08e82, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust-dl.so.1.0.0
>> /usr/lib/liblttng-ust-dl.so.1.0.0: ELF 64-bit LSB shared object, ARM
>> aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=6082ee88c9394319bc3adff16b0b3ea9f8d549ec, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust-fd.so.1.0.0
>> /usr/lib/liblttng-ust-fd.so.1.0.0: ELF 64-bit LSB shared object, ARM
>> aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=a2813245af91abe98615771dfd7d5f19b033a410, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust-fork.so.1.0.0
>> /usr/lib/liblttng-ust-fork.so.1.0.0: ELF 64-bit LSB shared object, ARM
>> aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=86afa53808502873830c02290f477d4ff8013afb, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust-libc-wrapper.so.1.0.0
>> /usr/lib/liblttng-ust-libc-wrapper.so.1.0.0: ELF 64-bit LSB shared
>> object, ARM aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=52f391875a378b5f2c46747a58020b86cb7c9a83, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust-pthread-wrapper.so.1.0.0
>> /usr/lib/liblttng-ust-pthread-wrapper.so.1.0.0: ELF 64-bit LSB shared
>> object, ARM aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=7127223a7e8ed67c6697b95ae1f8ac107df7e47e, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust-tracepoint.so.1.0.0
>> /usr/lib/liblttng-ust-tracepoint.so.1.0.0: ELF 64-bit LSB shared
>> object, ARM aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=5971b4d84ec1efe61c6d47c38e92de20569f0f49, with
>> debug_info, not stripped
>> # file /usr/lib/liblttng-ust.so.1.0.0
>> /usr/lib/liblttng-ust.so.1.0.0: ELF 64-bit LSB shared object, ARM
>> aarch64, version 1 (SYSV), dynamically linked,
>> BuildID[sha1]=ce7097ae9bbf42a02dccd386fdfbd37e3224858b, with
>> debug_info, not stripped
>>
>>
>> cutting some stuff out cause it's getting long again.
>>
>>>
>>> Sounds like `make check` for lttng-tools passed then?
>>
>> At first no.  But I think this is because I built the new lttng-tools
>> in my on target native environment and ran make check and forgot to do
>> make install first, so it was using the older version of lttng-tools.
>>
>> So then I ran make install of lttng-tools and even did a make clean
>> and rebuild of lttng-ust and re-installed it and ran make check on
>> both (and things looked a lot better) ... that's where those warnings
>> etc., I asked you about came from.
>>
>>>
>>> My understanding at this point is the unit tests are passing for
>>> LTTng-UST on your system, as are the unit and regression tests for
>>> LTTng-tools. The example programs shipped with LTTng-UST work on your
>>> system, as does the example from the documentation. The statedump
>>> tracepoints loaded from LTTng-UST are also working fine, as evinced by
>>> the program logs and the LTTng trace you shared.
>>>
>>> Despite my confusion about how exactly you're using the `hello world`
>>> tracepoint in your application (as you've now described several
>>> variations), the direction this points to for me are details related to
>>> how you're using LTTng-UST and/or how are your building and linking your
>>> application. To be clear, I don't mean to say that there is or is not an
>>> issue in LTTng-UST, but to point at where to examine next in detail
>>> including analysis of the produced object files.
>>
>> I compared the doc/examples/hello-static-lib to what I picked out of
>> the LTTng documentation on the web site "Quick start" section and the
>> traceprovider headder file is including stddef.h and mine isn't and
>> the doc/examples/hello-static-lib/hello.c code is doing a sighandler
>> and mine isn't doing any of that either.  I think I've probably posted
>> it before but will do it again.  Here is what I'm calling my "hello".
>> It's from the lttng documentation but I cut it down even further just
>> to make sure I didn't fat finger something.  Like I said before, the
>> full hello example from the documentation works.  But when I call
>> pretty much the same code from my app it seg faults.
>>
>> I don't know if the differences I see between my "hello" and the
>> "hello-static-lib" matter.
>>
>> hello-tp.h:
>>
>> #undef LTTNG_UST_TRACEPOINT_PROVIDER
>> #define LTTNG_UST_TRACEPOINT_PROVIDER hello_world
>>
>> #undef LTTNG_UST_TRACEPOINT_INCLUDE
>> #define LTTNG_UST_TRACEPOINT_INCLUDE "./hello-tp.h"
>>
>> #if !defined(_HELLO_TP_H) || defined(LTTNG_UST_TRACEPOINT_HEADER_MULTI_READ)
>> #define _HELLO_TP_H
>>
>> #include <lttng/tracepoint.h>
>>
>> LTTNG_UST_TRACEPOINT_EVENT(
>>     hello_world,
>>     my_first_tracepoint,
>>     LTTNG_UST_TP_ARGS(
>>         int, my_integer_arg
>>     ),
>>     LTTNG_UST_TP_FIELDS(
>>         lttng_ust_field_integer(int, my_integer_field, my_integer_arg)
>>     )
>> )
>>
>> #endif /* _HELLO_TP_H */
>>
>> #include <lttng/tracepoint-event.h>
>>
>> hello-tp.c:
>>
>> #define LTTNG_UST_TRACEPOINT_CREATE_PROBES
>>
>> #include "hello-tp.h"
>>
>>  From my_app:
>>
>> #define LTTNG_UST_TRACEPOINT_DEFINE
>> //#define LTTNG_UST_TRACEPOINT_PROBE_DYNAMIC_LINKAGE
>> #include "hello-tp.h"
>>
>> .
>> .
>> .
>> lttng_ust_tracepoint(hello_world, my_first_tracepoint, 23, "hi there!");
>>
>> In the above case the tpp is static but I've tried to make it a shared
>> object too (thus the commented out DYNAMIC_LINKAGE above) but get the
>> same result.
>>
>> Again, I think the issue is probably g++ and weak/hidden symbol
>> related and or TLS but that's based on the totality of what I've
>> experienced over the past year or so and seeing the
>> experiences/problems of others in the lttng-dev archives.
>>
>> Regards,
>>
>> Brian
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