I have a regression runner running on raspberry pi 32-bit architecture (in addition to a one on 64-bit raspberry pi and tons of X86). gcc-8 builds fine in both master and develop clang-9 builds fine on master clang-9 running the same command line, just on develop, has errors like this [1], finding basic includes: ``` "clang++-9" -c -x c++ -Wno-c99-extensions -std=c++2a -O0 -fno-inline -Wall -g --target=arm-pc-linux -Wno-deprecated-declarations -DBOOST_ALL_NO_LIB=1 -DBOOST_BEAST_ALLOW_DEPRECATED -DBOOST_BEAST_SEPARATE_COMPILATION -DBOOST_TEST_NO_AUTO_LINK=1 -I".." -o "/mnt/fs1/teeks99-05/run/results/boost/bin.v2/libs/accumulators/test/count.test/clang-linux-9~c++2a/debug/link-static/count.o" "../libs/accumulators/test/count.cpp" clang: warning: unknown platform, assuming -mfloat-abi=soft clang: warning: unknown platform, assuming -mfloat-abi=soft In file included from ../libs/accumulators/test/count.cpp:6: In file included from ../boost/test/unit_test.hpp:18: In file included from ../boost/test/test_tools.hpp:17: In file included from ../boost/config.hpp:44: ../boost/config/detail/select_stdlib_config.hpp:26:14: fatal error: 'cstddef' file not found # include <cstddef> ^~~~~~~~~ 1 error generated. ``` The relevant line of the user-config.jam is: using clang : 9~c++2a : clang++-9 : <cxxflags>"-Wno-c99-extensions -std=c++2a" ; The two command lines being run are: run.py --runner=teeks99-05-mc9-2a-32onarmv7l --toolsets=clang-9~c++2a \ "--bjam-options=-j4 address-model=32 --remove-test-targets" \ --comment=info.html --tag=master run.py --runner=teeks99-05-dc9-2a-32onarmv7l --toolsets=clang-9~c++2a \ "--bjam-options=-j4 address-model=32 --remove-test-targets" \ --comment=info.html --tag=develop Any ideas why master and develop would be different in this regard? Something with B2 changes? Thanks, Tom [1] https://www.boost.org/development/tests/develop/developer/output/teeks99-05-...