cmake findboost not working.

[Andrea Fiorito]

Hello,

here's another one trying to use boost with android (and possibly writing a portable cmakelists file).

The problem:
find_path appends the HINTS to an ndk path instead of using them as absolute path:

minimal reproducible example:
add on a cmakelists.txt the following:

set(CMAKE_FIND_DEBUG_MODE TRUE)
find_path(ABC_VAR
    NAMES         a_random_existing_file.txt
    HINTS         the_abs_path_of_the_file
    )
output on console similar to:

    find_path called with the following settings:
 
      VAR: Boost_INCLUDE_DIR
      NAMES: "boost/config.hpp"
      Documentation: Path to a file.
      Framework
        Only Search Frameworks: 0
        Search Frameworks Last: 0
        Search Frameworks First: 1
      AppBundle
        Only Search AppBundle: 0
        Search AppBundle Last: 0
        Search AppBundle First: 1
      CMAKE_FIND_USE_CMAKE_PATH: 0
      CMAKE_FIND_USE_CMAKE_ENVIRONMENT_PATH: 0
      CMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH: 0
      CMAKE_FIND_USE_CMAKE_SYSTEM_PATH: 0
 
    find_path considered the following locations:
.....
/Users/bloom/Library/Android/sdk/ndk/25.1.8937393/the_abs_path_of_the_file/a_random_existing_file.txt

How do I get rid of "/Users/bloom/Library/Android/sdk/ndk/25.1.8937393/" part?

as a recap:
I cloned boost4android and compiled it (https://github.com/moritz-wundke/Boost-for-Android)
I set the variables:
set(Boost_DEBUG ON)
    set(BOOST_ROOT ${BOOST_PATH}/${CMAKE_ANDROID_ARCH_ABI})
    set(BOOST_INCLUDEDIR ${BOOST_PATH}/${CMAKE_ANDROID_ARCH_ABI}/include/boost-1_82)
    set(BOOST_LIBRARYDIR ${BOOST_PATH}/${CMAKE_ANDROID_ARCH_ABI}/lib)
    set(Boost_LIB_PREFIX lib)

set(Boost_ADDITIONAL_VERSIONS "1.82.0" "1.82")
    set(Boost_NO_SYSTEM_PATHS TRUE)
    set(Boost_COMPILER "-clang-darwin")
    set(Boost_USE_STATIC_LIBS        ON)
    set(Boost_USE_MULTITHREADED      ON)
    set(Boost_USE_STATIC_RUNTIME    OFF)
    find_package( Boost 1.82.0 COMPONENTS serialization )

and I'm stuck at that find_path not found.
---------------------------------------------------------------------------------------
Also set(Boost_DEBUG ON) doesn't print anything out of the box because in findBoost.cmake the instruction that prints contains an extra word STATUS.
    message(STATUS "[ ${file}:${line} ] ${text}")
which sucks.

Who's gonna help this poor dev here? :D

[Andrea Fiorito]

Found a workaround, but probably a fix is needed somewhere to make it work out of the box.

My workaround was the line: set(CMAKE_SYSROOT "")

the full section looks like:

set(CMAKE_FIND_DEBUG_MODE TRUE)
set(Boost_DEBUG 0)
set(CMAKE_SYSROOT_OLD ${CMAKE_SYSROOT})
set(CMAKE_SYSROOT "")

set(BOOST_ROOT ${BOOST_PATH}/${CMAKE_ANDROID_ARCH_ABI})

message("LOOKING FOR BOOST ROOT IN " ${BOOST_ROOT})

set(BOOST_INCLUDEDIR ${BOOST_PATH}/${CMAKE_ANDROID_ARCH_ABI}/include/boost-1_82)
set(BOOST_LIBRARYDIR ${BOOST_PATH}/${CMAKE_ANDROID_ARCH_ABI}/lib)
set(Boost_LIB_PREFIX lib)

set(Boost_ADDITIONAL_VERSIONS "1.82.0" "1.82")
set(Boost_NO_SYSTEM_PATHS TRUE)
set(Boost_COMPILER "-clang-darwin")
set(Boost_USE_STATIC_LIBS ON)
set(Boost_USE_MULTITHREADED ON)
set(Boost_USE_STATIC_RUNTIME OFF)
find_package( Boost 1.82.0 COMPONENTS serialization )

if(Boost_FOUND)
message("Boost_FOUND is True")
include_directories(${Boost_INCLUDE_DIRS})
else()
message(FATAL_ERROR "Boost_FOUND is False")
endif()
set(CMAKE_SYSROOT ${CMAKE_SYSROOT_OLD})

........

target_link_libraries(${PROJECT_NAME} ${Boost_LIBRARIES})

funny thing is that for the openssl library (that suffered the same problem) I discovered first this workaround: set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY BOTH)
but also the line set(CMAKE_SYSROOT "") works.

the full section (with the first discovered workaround) looks like:
    set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY BOTH)
    message("LOOKING FOR OPEN_SSL LIBRARY IN " ${OPENSSL_LIB_DIR}/${CMAKE_ANDROID_ARCH_ABI})
    find_library(lib_crypto NAMES crypto
            HINTS ${OPENSSL_LIB_DIR}/${CMAKE_ANDROID_ARCH_ABI})

I'm not sure what is the impact to set the variable to empty in general, so i'm resetting to the old value just in case right after.

[Andrea Fiorito]

As update,

I was able to find a workaround with the line: set(CMAKE_SYSROOT "")

the full snippet of CMakelist looks like: (some options may be not necessary)

    set(CMAKE_FIND_DEBUG_MODE FALSE)

    set(Boost_DEBUG 0)
    set(CMAKE_SYSROOT_OLD ${CMAKE_SYSROOT})
    set(CMAKE_SYSROOT "")

    set(BOOST_ROOT ${BOOST_PATH}/${CMAKE_ANDROID_ARCH_ABI})

    message("LOOKING FOR BOOST ROOT IN " ${BOOST_ROOT})

    set(BOOST_INCLUDEDIR ${BOOST_PATH}/${CMAKE_ANDROID_ARCH_ABI}/include/boost-1_82)
    set(BOOST_LIBRARYDIR ${BOOST_PATH}/${CMAKE_ANDROID_ARCH_ABI}/lib)
    set(Boost_LIB_PREFIX lib)

    set(Boost_ADDITIONAL_VERSIONS "1.82.0" "1.82")
    set(Boost_NO_SYSTEM_PATHS TRUE)
    set(Boost_COMPILER "-clang-darwin")
    set(Boost_USE_STATIC_LIBS        ON)
    set(Boost_USE_MULTITHREADED      ON)
    set(Boost_USE_STATIC_RUNTIME    OFF)
    find_package( Boost 1.82.0 COMPONENTS serialization )

    if(Boost_FOUND)
        message("Boost_FOUND is True")
        include_directories(${Boost_INCLUDE_DIRS})
    else()
        message(FATAL_ERROR "Boost_FOUND is False")
    endif()
    set(CMAKE_SYSROOT ${CMAKE_SYSROOT_OLD})

Also, I had the same problem with find_library and openSSL (compiled for android obviously), the same solution works but the first one I found was using the line: set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY BOTH)

full snippet looks like:

    set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY BOTH)
    message("LOOKING FOR OPEN_SSL LIBRARY IN " ${OPENSSL_LIB_DIR}/${CMAKE_ANDROID_ARCH_ABI})
    find_library(lib_crypto NAMES crypto
            HINTS ${OPENSSL_LIB_DIR}/${CMAKE_ANDROID_ARCH_ABI})

A review of the settings for those variables, CMAKE_FIND_ROOT_PATH, CMAKE_SYSROOT may be needed imo to have findboost working out of the box.

On Wednesday, December 13, 2023 at 11:59:46 PM UTC Andrea Fiorito wrote: