"how do I set the default architecture when building boost?"
address-model=64 architecture=x86
Indeed, using these two commands as ./b2 address-model=64 architecture=x86 changes both of those properties as expected. however, if I use them in conjunction with *toolset=emscripten*, the problem I originally asked about persists: ./b2 toolset=emscripten address-model=64 architecture=x86 Performing configuration checks - default address-model : 32-bit - default architecture : none Building the Boost C++ Libraries. - symlinks supported : yes error: No best alternative for libs/context/build/asm_sources next alternative: required properties: <abi>aapcs <address-model>32 <architecture>arm <binary-format>elf <threading>multi <toolset>clang not matched next alternative: required properties: <abi>aapcs <address-model>32 <architecture>arm <binary-format>elf <threading>multi <toolset>gcc ... [more similar alternatives omitted for brevity --dab] - C++11 mutex : no - lockfree boost::atomic_flag : yes - Boost.Config Feature Check: cxx11_hdr_tuple : no - Boost.Config Feature Check: cxx11_lambdas : no - Boost.Config Feature Check: cxx11_noexcept : no - Boost.Config Feature Check: cxx11_nullptr : no - Boost.Config Feature Check: cxx11_rvalue_references : no - Boost.Config Feature Check: cxx11_template_aliases : no - Boost.Config Feature Check: cxx11_thread_local : no - Boost.Config Feature Check: cxx11_variadic_templates : no - Boost.Config Feature Check: cxx11_auto_declarations : no - Boost.Config Feature Check: cxx11_constexpr : no - Boost.Config Feature Check: cxx11_defaulted_functions : no - Boost.Config Feature Check: cxx11_final : no - Boost.Config Feature Check: cxx11_hdr_mutex : no *Error: ambiguity found when searching for best transformation* *Trying to produce type 'SEARCHED_LIB' from: * *Generators that succeeded:* * - searched-lib-generator* * - emscripten.searched-lib-generator* *First generator produced: * * - { %.no-action-icudata.SEARCHED_LIB }* *Second generator produced: * * - { %.no-action-icudata.SEARCHED_LIB }* to renew focus, the problem I am trying to solve is the last part there, ambiguity when searching for best transformation. it goes away if i disable icu, but it just yields another similar error. it was suggested that I need to provide the default architecture to solve the problem, but the way suggested to do that so far have not worked. your help is appreciated! Danielle Brake