Why Does CMake Fail to Detect LTTng in RHEL 8 for MsQuic, and What’s the Recommended Setup?

[CodeCraftrAks]

I’m facing challenges enabling LTTng tracing in MsQuic on RHEL 8, consistently seeing CMake Warning at CMakeLists.txt:390 (message): LTTng logging not found. Disabling logging during the build process. This happens despite installing LTTng dependencies via dnf and even building LTTng from source tarballs. Interestingly, the same build works seamlessly on Ubuntu with an LTTng PPA, but I’m struggling to replicate this success in RHEL 8. I suspect it might relate to the clog submodule’s integration or RHEL 8’s environment, and I’d appreciate your guidance.

[nibanks]

Unfortunately, I don't have a lot of experience with RHEL. Maybe @wfurt has some thoughts.

[wfurt]

there should be log AFAIK that shows what failed. Did you install just the libraries or headers as well? When building from sources you would have to convincer the build to look for headers in specific location - as far as I remember the install typically does not add the headers.

[CodeCraftrAks]

RPM Attempts: Installed lttng-ust, lttng-tools, and lttng-ust-devel or lttng-ust via dnf, which includes Headers like lttng/ust-config.h appear in /usr/include/lttng/, and libraries (liblttng-ust.so) in /usr/lib64/

[wfurt]

That is curious as it seems like the cmake only checks presence of the header

                check_include_file(lttng/ust-config.h HAS_LTTNG)
                if (NOT HAS_LTTNG)
                    message(WARNING "LTTng logging not found. Disabling logging")
                    set(QUIC_ENABLE_LOGGING OFF)
                else()

the cases I have seen broken in the past would were around dependencies. If ust-config.h depends on something else now in RH8, then the cmake attempt to check it would fail.

Maybe @omajid or @tmds have some more insight.

[CodeCraftrAks]

Correct, I'm also curious to know why it is failing. Does lttng/ust-config.h have other dependencies or is there a difference in LTTng versions? @omajid or @tmds, could you please provide some insights on the correct setup?

[omajid]

I can't reproduce this on RHEL 8.

$ git remote -v
origin  https://github.com/microsoft/msquic.git (fetch)
origin  https://github.com/microsoft/msquic.git (push)
$ git rev-parse HEAD
df075091c72fd40013115480079dbd16a2a40db1
$ rpm -q lttng-ust lttng-ust-devel lttng-tools
lttng-ust-2.8.1-11.el8.x86_64
lttng-ust-devel-2.8.1-11.el8.x86_64
lttng-tools-2.8.8-1.el8.x86_64
$ lttng -V
lttng (LTTng Trace Control) 2.8.8 - Isseki Nicho
$ mkdir build
$ cmake -S . -B build -DQUIC_ENABLE_LOGGING=true
-- CMAKE Version: 3.26.5
-- Source Dir: /home/omajid/msquic
-- Host System name: Linux
-- Setting policy 0091
-- System name: Linux
-- System version: 4.18.0-553.el8_10.x86_64
-- Platform version: 
-- Build type: Release
-- QUIC Platform: linux
-- Version Build ID: 0
-- Version Suffix: -private
-- UDP_SEGMENT is missing. Send performance will be reduced
-- Choosing lttng as default logging type for platform
-- Enabling OpenSsl configuration tests
-- Enabling CA file tests
CMake Warning at CMakeLists.txt:397 (message):
  LTTng with SDT integration does not work.  Disabling logging


-- libatomic not found. If build fails, install libatomic
-- Found libnuma: /usr/lib64/libnuma.so.1
-- numa.h not found. If build fails, install libnuma-dev
-- Enabling shared ephemeral port work around
-- Configuring for OpenSSL 1.1
-- Setting openssldir to /etc/pki/tls
-- Configuring OpenSSL: /home/omajid/msquic/submodules/openssl/config;CC=/usr/bin/cc;CXX=/usr/bin/c++ enable-tls1_3;no-makedepend;no-dgram;no-ssl3;no-psk;no-srp;no-zlib;no-egd;no-idea;no-rc5;no-rc4;no-afalgeng;no-comp;no-cms;no-ct;no-srp;no-srtp;no-ts;no-gost;no-dso;no-ec2m;no-tls1;no-tls1_1;no-tls1_2;no-dtls;no-dtls1;no-dtls1_2;no-ssl;no-ssl3-method;no-tls1-method;no-tls1_1-method;no-tls1_2-method;no-dtls1-method;no-dtls1_2-method;no-siphash;no-whirlpool;no-aria;no-bf;no-blake2;no-sm2;no-sm3;no-sm4;no-camellia;no-cast;no-md4;no-mdc2;no-ocb;no-rc2;no-rmd160;no-scrypt;no-seed;no-weak-ssl-ciphers;no-shared;no-tests;--openssldir="/etc/pki/tls";--prefix=/home/omajid/msquic/build/_deps/opensslquic-build/openssl
-- Configuring for OpenSSL
-- Configuring done (0.1s)
-- Generating done (0.0s)
-- Build files have been written to: /home/omajid/msquic/build

Can someone help me reproduce the issue?