libdbus library build notes

Linux

Integrate the osquery-toolchain, using the following file as a starting point: cmake/toolchain.cmake.

Then the osquery source code is needed, and also a build of the thirdparty_expat target. When built, set the OSQUERY_SOURCE_ROOT env var with the path to the root of the osquery source code, and OSQUERY_BUILD_ROOT with the build root.

Then configure dbus with the following command:

bash

cmake -S cmake -B b \
  -DOSQUERY_TOOLCHAIN_SYSROOT=/usr/local/osquery-toolchain \
  -DBUILD_SHARED_LIBS=OFF \
  -DDBUS_BUILD_TESTS=OFF \
  -DDBUS_ENABLE_VERBOSE_MODE=OFF \
  -DCMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH=OFF \
  -DCMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH=OFF \
  -DCMAKE_FIND_USE_CMAKE_SYSTEM_PATH=OFF \
  -DCMAKE_MAKE_PROGRAM=make \
  -DEXPAT_LIBRARY=${OSQUERY_BUILD_ROOT}/libs/src/expat/libthirdparty_expat.a \
  -DEXPAT_INCLUDE_DIR=${OSQUERY_SOURCE_ROOT}/libraries/cmake/source/expat/src/expat/lib

NOTE: We disable system search paths so that the find_package calls do not find system libraries like expat, but especially X11 and Glib, since we don't want to build against those.

Patch the source code to make it build with the dbus-noverbose-build.patch file.

Then build

bash

cmake --build b --verbose

Always check which additional preprocessor defines are passed to the compiler. Do not pass -Ddbus_1_EXPORTS but -DBUS_STATIC_BUILD. We do not need to pass --export-dynamic (or -rdynamic), because the backtrace created by the assert already works; we do need to pass -DDBUS_BUILT_R_DYNAMIC to get the backtrace though.

Copy the following generated files from the build folder:

config.h -> config/<arch>/config.h dbus/dbus-arch-deps.h -> generated/<arch>/dbus-arch-deps.h

Finally in the config.h file substitute the path prefix /usr/local/ with /usr, except for the paths that contain /var; in that case fully remove the /usr/local prefix, so that /var is at the root. This is needed because Dbus has to access files that on the system, not under some custom prefix.