Boost.Test linker error by use with precompiled headers (PCH) - c++

Question

I have a linker error when using Boost.Test with precompiled header (PCH) that does not occur without PCH. I use the dynamically linked library as described in Usage variants.
How can I fix the error to use Boost.Test also with PCH?
The problem occurs at least with Fedora and boost 1.73 (has only dynamic libraries) and g++ 10/clang 11.
$ cmake ../ && make
-- Configuring done
-- Generating done
-- Build files have been written to: /home/.../boost_test_pch/build
[ 33%] Building CXX object CMakeFiles/boost_utf_pch.dir/test_driver.cpp.o
[ 66%] Building CXX object CMakeFiles/boost_utf_pch.dir/test.cpp.o
[100%] Linking CXX executable boost_utf_pch
[100%] Built target boost_utf_pch
vs.
$ cmake -DEDA_ENABLE_PCH=TRUE ../ && make
-- Configuring done
-- Generating done
-- Build files have been written to: /home/.../boost_test_pch/build
[ 25%] Building CXX object CMakeFiles/boost_utf_pch.dir/cmake_pch.hxx.gch
[ 50%] Building CXX object CMakeFiles/boost_utf_pch.dir/test_driver.cpp.o
cc1plus: warning: /home/.../boost_test_pch/build/CMakeFiles/boost_utf_pch.dir/cmake_pch.hxx.gch: not used because `BOOST_TEST_DYN_LINK' is defined [-Winvalid-pch]
[ 75%] Building CXX object CMakeFiles/boost_utf_pch.dir/test.cpp.o
[100%] Linking CXX executable boost_utf_pch
/usr/bin/ld: /usr/lib/gcc/x86_64-redhat-linux/10/../../../../lib64/crt1.o: in function `_start':
(.text+0x24): undefined reference to `main'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/boost_utf_pch.dir/build.make:138: boost_utf_pch] Error 1
make[1]: *** [CMakeFiles/Makefile2:95: CMakeFiles/boost_utf_pch.dir/all] Error 2
make: *** [Makefile:103: all] Error 2
I can not do anything with the warning message before ...
Here the playground files:
CMakeLists.txt:
project(boost_utf_pch LANGUAGES CXX)
cmake_minimum_required(VERSION 3.18)
add_executable(${PROJECT_NAME} "")
find_package(Boost 1.73.0 REQUIRED COMPONENTS
unit_test_framework)
target_sources(${PROJECT_NAME} PRIVATE
test_driver.cpp test.cpp)
target_link_libraries(${PROJECT_NAME} PRIVATE
Boost::unit_test_framework)
set_source_files_properties(test_driver.cpp
APPEND PROPERTIES COMPILE_DEFINITIONS "BOOST_TEST_DYN_LINK")
option(EDA_ENABLE_PCH "Enable PCH" OFF)
if (EDA_ENABLE_PCH)
target_precompile_headers(${PROJECT_NAME} PRIVATE pch.hpp)
endif()
pch.hpp
#pragma once
#include <boost/test/unit_test.hpp>
test.cpp
#include <boost/test/unit_test.hpp>
BOOST_AUTO_TEST_SUITE( my_test )
BOOST_AUTO_TEST_CASE( test_case1 )
{
BOOST_TEST_WARN( sizeof(int) < 4U );
}
BOOST_AUTO_TEST_SUITE_END()
test_driver.cpp
#define BOOST_TEST_MODULE "Boost.UTF PCH Test Suite"
#include <boost/test/unit_test.hpp>

Answer 1

Alan Birtles got the hint into the right direction. I was not aware of the influence of the compiler switch BOOST_TEST_DYN_LINK for the single file in the context of PCH here. A definition for all files of the project in the style of:
target_compile_definitions(${PROJECT_NAME} PRIVATE
"BOOST_TEST_DYN_LINK")
incomprehensibly does not solve the problem. Only after setting the property SKIP_PRECOMPILE_HEADERS for driver 'main' it compiles and links as expected:
project(boost_utf_pch LANGUAGES CXX)
cmake_minimum_required(VERSION 3.18)
add_executable(${PROJECT_NAME} "")
find_package(Boost 1.73.0 REQUIRED COMPONENTS
unit_test_framework)
target_sources(${PROJECT_NAME} PRIVATE
test_driver.cpp test.cpp)
target_link_libraries(${PROJECT_NAME} PRIVATE
Boost::unit_test_framework)
set_source_files_properties(test_driver.cpp
APPEND PROPERTIES COMPILE_DEFINITIONS "BOOST_TEST_DYN_LINK")
set_source_files_properties(test_driver.cpp
PROPERTIES SKIP_PRECOMPILE_HEADERS ON)
option(EDA_ENABLE_PCH "Enable PCH" ON)
if (EDA_ENABLE_PCH)
target_precompile_headers(${PROJECT_NAME} PRIVATE pch.hpp)
endif()