boost v1.66 boost test linker LNK2005 errors

[shanepowell]

Compiler : VC2017 v15.5.2
Branch : master
Boost : 1.66
Triplet : x86-windows, x64-windows

Error :

1>boost_unit_test_framework-vc140-mt-gd-1_66.lib(boost_unit_test_framework-vc141-mt-gd-x32-1_66.dll) : error LNK2005: "public: static class boost::unit_test::unit_test_log_t & __cdecl boost::unit_test::singleton::instance(void)" (?instance@?$singleton@Vunit_test_log_t@unit_test@boost@@@unit_test@boost@@SAAAVunit_test_log_t@23@XZ) already defined in boost_test_exec_monitor-vc140-mt-gd-1_66.lib(test_tools.obj)
....

Might be related to : #2057

Repro:
Create VC2017 C++ console application and paste following:

#define BOOST_TEST_MODULE MyTest
#include <boost/test/unit_test.hpp>

int add(int i, int j) { return i + j; }

BOOST_AUTO_TEST_CASE(my_test)
{
BOOST_CHECK(add(2, 2) == 4); // #1 continues on error
}

Compile and link release or debug, win32 or x64

Workaround: remove 'boost_test_exec_monitor-vc140-mt-gd-1_66.lib' from the installed lib directories

[ras0219-msft]

This is a regression back to the bad behavior described in #2057.

[ras0219-msft]

Thank you for reporting this; the fix is pushed to master!