`NO_CRTP` mode enabled but explicit `this` parameter is not supported

[Becheler]

Hello people!

I am having this error when installing mp-units:

• in gitlab CI
• on a Ubuntu-24.04 docker image
• with Conan 2,
• in Debug mode
• gcc-14 with C++23 enabled

NO_CRTP mode enabled but explicit this parameter is not supported

Any idea what is going on ? :) Thanks!

Here is the full log:

mp-units/2.2.1: Calling source() in /root/.conan2/p/mp-un083d9aa103ca4/s/src
mp-units/2.2.1: Unzipping v2.2.1.tar.gz to .
-------- Installing package mp-units/2.2.1 (8 of 8) --------
mp-units/2.2.1: Building from source
mp-units/2.2.1: Package mp-units/2.2.1:da39a3ee5e6b4b0d3255bfef95601890afd80709
mp-units/2.2.1: Building your package in /root/.conan2/p/b/mp-uncfde0d364fde4/b
mp-units/2.2.1: Calling generate()
mp-units/2.2.1: Generators folder: /root/.conan2/p/b/mp-uncfde0d364fde4/b/build/Debug/generators
mp-units/2.2.1: CMakeToolchain generated: conan_toolchain.cmake
mp-units/2.2.1: CMakeToolchain generated: /root/.conan2/p/b/mp-uncfde0d364fde4/b/build/Debug/generators/CMakePresets.json
mp-units/2.2.1: CMakeToolchain generated: /root/.conan2/p/mp-un083d9aa103ca4/s/src/CMakeUserPresets.json
mp-units/2.2.1: Generating aggregated env files
mp-units/2.2.1: Generated aggregated env files: ['conanbuild.sh', 'conanrun.sh']
mp-units/2.2.1: Calling build()
mp-units/2.2.1: Running CMake.configure()
mp-units/2.2.1: RUN: cmake -G "Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE="generators/conan_toolchain.cmake" -DCMAKE_INSTALL_PREFIX="/root/.conan2/p/b/mp-uncfde0d364fde4/p" -DMP_UNITS_API_STD_FORMAT="ON" -DMP_UNITS_API_STRING_VIEW_RET="ON" -DMP_UNITS_API_NO_CRTP="ON" -DMP_UNITS_API_CONTRACTS="GSL-LITE" -DCMAKE_POLICY_DEFAULT_CMP0091="NEW" -DCMAKE_BUILD_TYPE="Debug" "/root/.conan2/p/mp-un083d9aa103ca4/s/src/src"
-- Using Conan toolchain: /root/.conan2/p/b/mp-uncfde0d364fde4/b/build/Debug/generators/conan_toolchain.cmake
-- Conan toolchain: Defining architecture flag: -m64
-- Conan toolchain: C++ Standard 23 with extensions OFF
-- The CXX compiler identification is GNU 13.2.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- MP_UNITS_BUILD_AS_SYSTEM_HEADERS: OFF
-- MP_UNITS_BUILD_CXX_MODULES: OFF
-- Checking C++ feature test macro '__cpp_lib_format'
-- Checking C++ feature test macro '__cpp_lib_format' - SUCCESS
-- Checking C++ feature test macro '__cpp_constexpr >= 202211L'
-- Checking C++ feature test macro '__cpp_constexpr >= 202211L' - SUCCESS
-- Checking C++ feature test macro '__cpp_explicit_this_parameter'
-- Checking C++ feature test macro '__cpp_explicit_this_parameter' - FAIL
-- MP_UNITS_API_STD_FORMAT: ON
-- MP_UNITS_API_STRING_VIEW_RET: ON
-- MP_UNITS_API_NO_CRTP: ON
-- MP_UNITS_API_FREESTANDING: OFF
-- MP_UNITS_API_CONTRACTS: GSL-LITE
CMake Error at CMakeLists.txt:115 (message):
  `NO_CRTP` mode enabled but explicit `this` parameter is not supported
-- Configuring incomplete, errors occurred!
mp-units/2.2.1: ERROR: 
Package 'da39a3ee5e6b4b0d3255bfef95601890afd80709' build failed
mp-units/2.2.1: WARN: Build folder /root/.conan2/p/b/mp-uncfde0d364fde4/b/build/Debug
ERROR: mp-units/2.2.1: Error in build() method, line 222
	cmake.configure(build_script_folder="src")
	ConanException: Error 1 while executing

[mpusz]

It seems that Conan (and also you 😉) thought you used gcc-14. But CMake actually reports gcc-13 being used.

Could you please check your Conan profile or conan install command line.

[Becheler]

Conan detects indeed gcc13 but I overwrite the settings when invoking install

$ conan profile detect
detect_api: Found cc=gcc- 13.2.0
detect_api: gcc>=5, using the major as version
detect_api: gcc C++ standard library: libstdc++11
Detected profile:
WARN: This profile is a guess of your environment, please check it.
WARN: The output of this command is not guaranteed to be stable and can change in future Conan versions.
WARN: Use your own profile files for stability.
Saving detected profile to /root/.conan2/profiles/default
[settings]
arch=x86_64
build_type=Release
compiler=gcc
compiler.cppstd=gnu17
compiler.libcxx=libstdc++11
compiler.version=13
os=Linux
$ conan install . -b=missing -of=build/conan -s="compiler=gcc" -s="compiler.version=14" -s="build_type=$build_type" -s="compiler.cppstd=$std"
======== Input profiles ========
Profile host:
[settings]
arch=x86_64
build_type=Debug
compiler=gcc
compiler.cppstd=23
compiler.libcxx=libstdc++11
compiler.version=14
os=Linux
Profile build:
[settings]
arch=x86_[64](https:blabla/-/jobs/202154#L64)
build_type=Release
compiler=gcc
compiler.cppstd=gnu17
compiler.libcxx=libstdc++11
compiler.version=13
os=Linux

It looks like the build profile is not updated correctly 🤔

[mpusz]

Overriding the compiler version does nothing. Conan does not know the path to the compiler to run. You need to provide proper path to executables. See the profile example in the "Conan quick intro" here: https://mpusz.github.io/mp-units/latest/getting_started/installation_and_usage/#obtaining-dependencies.

[mpusz]

@Becheler, did you manage to solve your problem? Can we close this issue?

[Becheler]

Hi @mpusz !

Sorry for my late answer and thank you for your answer. It solved it and the pipeline could run smoothly.

Thank you so much again for your support!