Hello, Boost folks. :)
I tried to remove this undocumented internal macro from our STL because we used it in only one place, but this broke Boost:
#define _FPOSOFF(fp) ((long long)(fp))
...patience...
...found 722 targets...
...updating 18 targets...
common.mkdir build\boost\bin.v2\libs
common.mkdir build\boost\bin.v2\libs\iostreams
common.mkdir build\boost\bin.v2\libs\iostreams\build
common.mkdir build\boost\bin.v2\libs\iostreams\build\msvc-99
common.mkdir build\boost\bin.v2\libs\iostreams\build\msvc-99\debug
common.mkdir build\boost\bin.v2\libs\iostreams\build\msvc-99\debug\link-static
common.mkdir build\boost\bin.v2\libs\iostreams\build\msvc-99\debug\link-static\threading-multi
compile-c-c++ build\boost\bin.v2\libs\iostreams\build\msvc-99\debug\link-static\threading-multi\file_descriptor.obj
file_descriptor.cpp
d:\src\vc\wcfb01\qa\vc\FE\3rdpartycomp\boost_1_60_0\boost/iostreams/positioning.hpp(107): error C3861: '_FPOSOFF': identifier not found
libs\iostreams\src\file_descriptor.cpp(265): warning C4244: 'argument': conversion from 'std::streamsize' to 'DWORD', possible loss of data
libs\iostreams\src\file_descriptor.cpp(289): warning C4244: 'argument': conversion from 'std::streamsize' to 'DWORD', possible loss of data
cl /Zm800 -nologo @"build\boost\bin.v2\libs\iostreams\build\msvc-99\debug\link-static\threading-multi\file_descriptor.obj.rsp"
...failed compile-c-c++ build\boost\bin.v2\libs\iostreams\build\msvc-99\debug\link-static\threading-multi\file_descriptor.obj...
compile-c-c++ build\boost\bin.v2\libs\iostreams\build\msvc-99\debug\link-static\threading-multi\mapped_file.obj
mapped_file.cpp
d:\src\vc\wcfb01\qa\vc\FE\3rdpartycomp\boost_1_60_0\boost/iostreams/positioning.hpp(107): error C3861: '_FPOSOFF': identifier not found
libs\iostreams\src\mapped_file.cpp(59): warning C4244: 'return': conversion from 'const boost::iostreams::stream_offset' to '::size_t', possible loss of data
libs\iostreams\src\mapped_file.cpp(325): warning C4244: 'argument': conversion from 'boost::iostreams::stream_offset' to 'SIZE_T', possible loss of data
cl /Zm800 -nologo @"build\boost\bin.v2\libs\iostreams\build\msvc-99\debug\link-static\threading-multi\mapped_file.obj.rsp"
...failed compile-c-c++ build\boost\bin.v2\libs\iostreams\build\msvc-99\debug\link-static\threading-multi\mapped_file.obj...
...skipped