It is possible to build boost-json outside of the boost tree with b2?

[autoantwort]

In vcpkg every boost lib is its own lib, so we do not clone the boost meta repo recursively and build the whole thing. Every lib is cloned and build separately.
So this lib will be build with the following command:
cd /mnt/vcpkg-ci/buildtrees/boost-json/src/ost-1.75.0-71b8ba6dd3.clean/build && /mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/b2 --user-config=/mnt/vcpkg-ci/buildtrees/boost-json/x64-linux-rel/user-config.jam --stagedir=/mnt/vcpkg-ci/buildtrees/boost-json/x64-linux-rel/stage --build-dir=/mnt/vcpkg-ci/buildtrees/boost-json/x64-linux-rel runtime-link=static link=static address-model=64 architecture=x86 target-os=linux toolset=gcc threadapi=pthread -sZLIB_BINARY=z -sZLIB_LIBPATH="/mnt/vcpkg-ci/installed/x64-linux/lib/libz.a" -sBZIP2_BINARY=bz2 -sBZIP2_LIBPATH="/mnt/vcpkg-ci/installed/x64-linux/lib/libbz2.a" variant=release --layout=system --with-atomic --with-random --with-date_time --with-filesystem --with-system --with-thread --with-chrono -sZLIB_INCLUDE="/mnt/vcpkg-ci/installed/x64-linux/include" -sBZIP2_INCLUDE="/mnt/vcpkg-ci/installed/x64-linux/include" -sICU_PATH="/mnt/vcpkg-ci/installed/x64-linux" -j16 -sBOOST_ROOT=/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build -sBOOST_BUILD_PATH=/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build --debug-configuration --ignore-site-config --hash -q threading=multi debug-symbols=on stage
This works for the most libs, but not for this one because is looks outside of this repository:

json/Jamfile

Line 10 in aae1863

import ../config/checks/config : requires ;

For completeness the resulting error log:

Click to expand

notice: found boost-build.jam at /mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/boost-build.jam
notice: loading B2 from /mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/kernel/bootstrap.jam
notice: Site configuration files will be ignored due to the
notice: --ignore-site-config command-line option.
notice: Loading explicitly specified user configuration file:
    /mnt/vcpkg-ci/buildtrees/boost-json/x64-linux-rel/user-config.jam
notice: Searching '/mnt/vcpkg-ci/buildtrees/boost-json/x64-linux-rel' for user-config configuration file 'user-config.jam'.
notice: Loading user-config configuration file 'user-config.jam' from '/mnt/vcpkg-ci/buildtrees/boost-json/x64-linux-rel'.
notice: will use '/usr/bin/c++' for gcc, condition <toolset>gcc-5.4.1
notice: using gcc libraries :: <toolset>gcc-5.4.1 :: /usr/bin /usr/lib /usr/lib32 /usr/lib64
notice: using gcc archiver :: <toolset>gcc-5.4.1 :: /usr/bin/ar
notice: using gcc ranlib :: <toolset>gcc-5.4.1 :: /usr/bin/ranlib
warning: toolset gcc initialization: can not find tool windres
warning: initialized from /mnt/vcpkg-ci/buildtrees/boost-json/x64-linux-rel/user-config.jam:22
notice: using rc compiler :: <toolset>gcc-5.4.1 :: /usr/bin/as
config.jam: No such file or directory
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/kernel/modules.jam:314: in modules.import
IMPORT error: rule "requires" unknown in module "config".
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/build/project.jam:1121: in import
../Jamfile:10: in load-aux
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/build/project.jam:378: in load-jamfile
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/build/project.jam:64: in load
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/build/project.jam:109: in load-parent
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/build/project.jam:513: in initialize
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/build/project.jam:348: in load-jamfile
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/build/project.jam:64: in load
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/build/project.jam:142: in project.find
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/build-system.jam:618: in load
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/kernel/modules.jam:295: in import
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/src/kernel/bootstrap.jam:139: in boost-build
/mnt/vcpkg-ci/installed/x64-linux/tools/boost-build/boost-build.jam:8: in module scope
ninja: build stopped: subcommand failed.

Is there a way to build this lib with b2 outside of the boost tree?

[grisumbras]

I'm confused. Are you trying to build the library in standalone mode or are you trying to build it in Boost mode, but not in the Boost tree?

[autoantwort]

are you trying to build it in Boost mode, but not in the Boost tree?

This one. I have updated the Issue

[grisumbras]

Well, it is technically possible but probably not very easy. Aside from requiring Boost.Config jam files you also need target /boost//container defined (I don't think we link to Boost.Container any more but the target is still used).

[vinniefalco]

Building outside the boost tree with b2 is possible, but I think what you're really asking is "Does the Jamfile that comes with Boost.JSON support out-of-tree builds" to which the answer is an emphatic no. Bjam and CMake are not my specialties so I only can support what is necessary for my workflow and for the Boost libraries.

[grisumbras]

BTW, I've grepped for other cases where Boost.Config jam module is used. Aside from tests and examples, I've got these:

context/build/Jamfile.v2|15| 12: import ../../config/checks/config : requires ;
fiber/build/Jamfile.v2|12| 11:import ../../config/checks/config : requires ;
beast/Jamfile|17| 8:import ../config/checks/config : requires ;
contract/build/boost_contract_build.jam|52| 11:import ../../config/checks/config : requires ;
multiprecision/config/Jamfile.v2|8| 11:import ../../config/checks/config : requires ;

At least a few of them aren't header only.

[autoantwort]

Yeah in the other ports something similar to the following is done:

file(READ "${SOURCE_PATH}/build/Jamfile" _contents)
string(REPLACE "import ../../config/checks/config" "import config/checks/config" _contents "${_contents}")
file(WRITE "${SOURCE_PATH}/build/Jamfile" "${_contents}")

file(READ "${SOURCE_PATH}/Jamfile" _contents)
string(REPLACE "import ../config/checks/config" "import build/config/checks/config" _contents "${_contents}")
file(WRITE "${SOURCE_PATH}/Jamfile" "${_contents}")

file(COPY "${CURRENT_INSTALLED_DIR}/share/boost-config/checks" DESTINATION "${SOURCE_PATH}/build/config")

But with this patches I got the following errors:

notice: found boost-build.jam at /Users/leanderSchulten/git_projekte/Lichtsteuerung/vcpkg_installed/arm64-osx/tools/boost-build/boost-build.jam
notice: loading B2 from /Users/leanderSchulten/git_projekte/Lichtsteuerung/vcpkg_installed/arm64-osx/tools/boost-build/src/kernel/bootstrap.jam
notice: Site configuration files will be ignored due to the
notice: --ignore-site-config command-line option.
notice: Loading explicitly specified user configuration file:
    /Users/leanderSchulten/git_projekte/Lichtsteuerung/vcpkg/buildtrees/boost-json/x64-osx-rel/user-config.jam
notice: Searching '/Users/leanderSchulten/git_projekte/Lichtsteuerung/vcpkg/buildtrees/boost-json/x64-osx-rel' for user-config configuration file 'user-config.jam'.
notice: Loading user-config configuration file 'user-config.jam' from '/Users/leanderSchulten/git_projekte/Lichtsteuerung/vcpkg/buildtrees/boost-json/x64-osx-rel'.
notice: will use '/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++' for gcc, condition <toolset>gcc-5.4.1
notice: using gcc libraries :: <toolset>gcc-5.4.1 :: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib32 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib64
notice: using gcc archiver :: <toolset>gcc-5.4.1 :: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ar
notice: using gcc ranlib :: <toolset>gcc-5.4.1 :: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib
warning: toolset gcc initialization: can not find tool windres
warning: initialized from /Users/leanderSchulten/git_projekte/Lichtsteuerung/vcpkg/buildtrees/boost-json/x64-osx-rel/user-config.jam:22
notice: using rc compiler :: <toolset>gcc-5.4.1 :: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/as
notice: [cmdline-cfg] toolset clang not previously configured; attempting to auto-configure now
notice: will use 'clang++' for clang-darwin, condition <toolset>clang-12.0
Performing configuration checks

    - cxx11_variadic_templates : yes
    - cxx11_template_aliases   : yes
    - cxx11_hdr_tuple          : yes
    - cxx11_decltype           : yes
    - cxx11_constexpr          : yes
    - cxx11_alignas            : yes
error: Unable to find file or target named
error:     '/boost//container'
error: referred to from project at
error:     '../build'

ninja: build stopped: subcommand failed.

PS: I also tried it in the past, but didn't know what to with the error. But you also said that this will happen

[autoantwort]

Ok, I simply removed this line:

json/build/Jamfile

Line 17 in aae1863

<library>/boost//container/<warnings-as-errors>off

Works now :D
Thank you!

[vinniefalco]

LOL.... that's serendipitous :)