[question] CXX flags not applied with Android toolchain

[cocoza4]

What is your question?

Hi there,

I'm crossing compiling a simple hello package for aarch64-linux-android with android-ndk-r21. In my profile, I specified tools.build:cxxflags to pass additional flags, even though these flags appear in conan_toolchain.cmake, it actually didn't get applied during the build.

Steps to reproduce

1. download Android NDK from https://dl.google.com/android/repository/android-ndk-r21-linux-x86_64.zip
2. create a test hello package with conan new hello/0.1 -m=cmake_lib
3. create an aarch64-linux-android profile, content below
4. run VERBOSE=1 conan create . -pr:h /workspace/conan/profiles/aarch64-linux-android -pr:b default -tf=None

Some logs

/root/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ --target=aarch64-none-linux-android21 --gcc-toolchain=/root/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64 --sysroot=/root/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/sysroot  -I/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/include -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security   -O2 -DNDEBUG  -fPIC -MD -MT CMakeFiles/hello.dir/src/hello.cpp.o -MF CMakeFiles/hello.dir/src/hello.cpp.o.d -o CMakeFiles/hello.dir/src/hello.cpp.o -c /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/src/hello.cpp

conan_toolchain.cmake

# Conan automatically generated toolchain file
# DO NOT EDIT MANUALLY, it will be overwritten

# Avoid including toolchain file several times (bad if appending to variables like
#   CMAKE_CXX_FLAGS. See https://github.com/android/ndk/issues/323
include_guard()

message(STATUS "Using Conan toolchain: ${CMAKE_CURRENT_LIST_FILE}")

if(${CMAKE_VERSION} VERSION_LESS "3.15")
    message(FATAL_ERROR "The 'CMakeToolchain' generator only works with CMake >= 3.15")
endif()

# New toolchain things
set(ANDROID_PLATFORM android-21)
set(ANDROID_STL c++_shared)
set(ANDROID_ABI arm64-v8a)
include(/root/android-ndk-r21/build/cmake/android.toolchain.cmake)

message(STATUS "Conan toolchain: Setting CMAKE_POSITION_INDEPENDENT_CODE=ON (options.fPIC)")
set(CMAKE_POSITION_INDEPENDENT_CODE ON CACHE BOOL "Position independent code")

# Extra c, cxx, linkflags and defines
string(APPEND CONAN_CXX_FLAGS " -fPIC -pthread -fstrict-aliasing -ffast-math -O3 -fvisibility=hidden -fvisibility-inlines-hidden -fno-omit-frame-pointer")
string(APPEND CONAN_C_FLAGS " -fPIC -pthread -fstrict-aliasing -ffast-math -O3 -fvisibility=hidden")

if(DEFINED CONAN_CXX_FLAGS)
  string(APPEND CMAKE_CXX_FLAGS_INIT " ${CONAN_CXX_FLAGS}")
endif()
if(DEFINED CONAN_C_FLAGS)
  string(APPEND CMAKE_C_FLAGS_INIT " ${CONAN_C_FLAGS}")
endif()
if(DEFINED CONAN_SHARED_LINKER_FLAGS)
  string(APPEND CMAKE_SHARED_LINKER_FLAGS_INIT " ${CONAN_SHARED_LINKER_FLAGS}")
endif()
if(DEFINED CONAN_EXE_LINKER_FLAGS)
  string(APPEND CMAKE_EXE_LINKER_FLAGS_INIT " ${CONAN_EXE_LINKER_FLAGS}")
endif()

get_property( _CMAKE_IN_TRY_COMPILE GLOBAL PROPERTY IN_TRY_COMPILE )
if(_CMAKE_IN_TRY_COMPILE)
    message(STATUS "Running toolchain IN_TRY_COMPILE")
    return()
endif()

set(CMAKE_FIND_PACKAGE_PREFER_CONFIG ON)

# Definition of CMAKE_MODULE_PATH
# the generators folder (where conan generates files, like this toolchain)
list(PREPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR})

# Definition of CMAKE_PREFIX_PATH, CMAKE_XXXXX_PATH
# The Conan local "generators" folder, where this toolchain is saved.
list(PREPEND CMAKE_PREFIX_PATH ${CMAKE_CURRENT_LIST_DIR} )

if(NOT DEFINED CMAKE_FIND_ROOT_PATH_MODE_PACKAGE OR CMAKE_FIND_ROOT_PATH_MODE_PACKAGE STREQUAL "ONLY")
    set(CMAKE_FIND_ROOT_PATH_MODE_PACKAGE "BOTH")
endif()
if(NOT DEFINED CMAKE_FIND_ROOT_PATH_MODE_PROGRAM OR CMAKE_FIND_ROOT_PATH_MODE_PROGRAM STREQUAL "ONLY")
    set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM "BOTH")
endif()
if(NOT DEFINED CMAKE_FIND_ROOT_PATH_MODE_LIBRARY OR CMAKE_FIND_ROOT_PATH_MODE_LIBRARY STREQUAL "ONLY")
    set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY "BOTH")
endif()
if(NOT DEFINED CMAKE_FIND_ROOT_PATH_MODE_INCLUDE OR CMAKE_FIND_ROOT_PATH_MODE_INCLUDE STREQUAL "ONLY")
    set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE "BOTH")
endif()

if (DEFINED ENV{PKG_CONFIG_PATH})
set(ENV{PKG_CONFIG_PATH} "/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release/generators:$ENV{PKG_CONFIG_PATH}")
else()
set(ENV{PKG_CONFIG_PATH} "/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release/generators:")
endif()

message(STATUS "Conan toolchain: Setting BUILD_SHARED_LIBS = OFF")
set(BUILD_SHARED_LIBS OFF CACHE BOOL "Build shared libraries")

set(CMAKE_INSTALL_PREFIX "/root/.conan/data/hello/0.1/_/_/package/a2ccebaee30b07c93935ff3643d57c8239e9ee4f")
set(CMAKE_INSTALL_BINDIR "bin")
set(CMAKE_INSTALL_SBINDIR "bin")
set(CMAKE_INSTALL_LIBEXECDIR "bin")
set(CMAKE_INSTALL_LIBDIR "lib")
set(CMAKE_INSTALL_INCLUDEDIR "include")
set(CMAKE_INSTALL_OLDINCLUDEDIR "include")

As you can see, -fvisibility-inlines-hidden -fno-omit-frame-pointer appear in the toolchain but it didn't get applied when running cmake. How can I make these flags get applied?

aarch64-linux-android

target_host=aarch64-linux-android
android_ndk=/root/android-ndk-r21
toolchain=$android_ndk/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/aarch64-linux-android/bin
api_level=21

clang_cflags="-fPIC -pthread -fstrict-aliasing -ffast-math -O3 -fvisibility=hidden"
clang_cxxflags="$clang_cflags -fvisibility-inlines-hidden -fno-omit-frame-pointer"

[settings]
arch=armv8
build_type=Release
compiler=clang
compiler.libcxx=c++_shared
compiler.version=9
os=Android
os.api_level=$api_level

[tool_requires]
[options]

[conf]
tools.env.virtualenv:auto_use=True
tools.android:ndk_path=$android_ndk
tools.build:cflags=["$clang_cflags"]
tools.build:cxxflags=["$clang_cxxflags"]

[buildenv]
CHOST=$target_host
AR=$toolchain/ar
CC=$target_host$api_level-clang
CXX=$target_host$api_level-clang++
AS=$CC
LD=$toolchain/ld
RANLIB=$toolchain/ranlib
STRIP=$toolchain/strip

Have you read the CONTRIBUTING guide?

• I've read the CONTRIBUTING guide

[cocoza4]

@memsharded any idea about the fix? thanks

[memsharded]

Hi @cocoza4

I am trying this (on Windows), and it seems to be working fine here:

C:\ws\android\android-ndk-r23b\toolchains\llvm\prebuilt\windows-x86_64\bin\clang++.exe --target=aarch64-none-linux-android21 --sysroot=C:/ws/android/android-ndk-r23b/toolchains/llvm/prebuilt/windows-x86_64/sysroot  -IC:\Users\Diego\.conan\data\hello\0.1\_\_\build\a2ccebaee30b07c93935ff3643d57c8239e9ee4f\include -fPIC -pthread -fstrict-aliasing -ffast-math -O3 -fvisibility=hidden -fvisibility-inlines-hidden -fno-omit-frame-pointer   -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security -fexceptions -frtti -stdlib=libc++ -O3 -DNDEBUG -fPIC -MD -MT CMakeFiles/hello.dir/src/hello.cpp.o -MF CMakeFiles\hello.dir\src\hello.cpp.o.d -o CMakeFiles\hello.dir\src\hello.cpp.o -c C:\Users\Diego\.conan\data\hello\0.1\_\_\build\a2ccebaee30b07c93935ff3643d57c8239e9ee4f\src\hello.cpp

The lines

-fPIC -pthread -fstrict-aliasing -ffast-math -O3 -fvisibility=hidden -fvisibility-inlines-hidden -fno-omit-frame-pointer 

Are all there, not sure why it wouldn't be working on your side.

Also, it is not necessary to detail the full environment [buildenv] as you do, I think the Android toolchain is able to manage it. This profile works fine for me:

target_host=aarch64-linux-android
android_ndk=C:\ws\android\android-ndk-r23b
api_level=21

clang_cflags="-fPIC -pthread -fstrict-aliasing -ffast-math -O3 -fvisibility=hidden"
clang_cxxflags="$clang_cflags -fvisibility-inlines-hidden -fno-omit-frame-pointer"

[settings]
arch=armv8
build_type=Release
compiler=clang
compiler.libcxx=c++_shared
compiler.version=9
os=Android
os.api_level=$api_level

[tool_requires]
[options]

[conf]
tools.env.virtualenv:auto_use=True
tools.android:ndk_path=$android_ndk
tools.build:cflags=["$clang_cflags"]
tools.build:cxxflags=["$clang_cxxflags"]

[buildenv]
PATH+=(path)C:\ws\msys64\mingw64\bin

[memsharded]

Maybe you want to report the Conan version, and also the CMake version (recommended >3.19 at least for Android), just in case.

[cocoza4]

@memsharded I'm on Conan 1.58, CMake 3.22.1

[memsharded]

If you can please share your full log/output, that might have some extra hint.

[cocoza4]

If you can please share your full log/output, that might have some extra hint.

root@peeranat:/workspace/3rdparty/hello# VERBOSE=1 conan create . -pr:h /workspace/conan/profiles/aarch64-linux-android -pr:b default -tf=None
Exporting package recipe
hello/0.1 exports_sources: Copied 1 '.txt' file: CMakeLists.txt
hello/0.1 exports_sources: Copied 1 '.cpp' file: hello.cpp
hello/0.1 exports_sources: Copied 1 '.h' file: hello.h
hello/0.1: The stored package has not changed
hello/0.1: Exported revision: bb4d07e0897a612e65c02400af2276aa
Configuration (profile_host):
[settings]
arch=armv8
build_type=Release
compiler=clang
compiler.libcxx=c++_shared
compiler.version=9
os=Android
os.api_level=21
[options]
[build_requires]
[env]
[conf]
tools.env.virtualenv:auto_use=True
tools.android:ndk_path=/root/android-ndk-r21
tools.build:cflags=['-fPIC -pthread -fstrict-aliasing -ffast-math -O3 -fvisibility=hidden']
tools.build:cxxflags=['-fPIC -pthread -fstrict-aliasing -ffast-math -O3 -fvisibility=hidden -fvisibility-inlines-hidden -fno-omit-frame-pointer']
[buildenv]
CHOST=aarch64-linux-android
AR=/root/android-ndk-r21/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/aarch64-linux-android/bin/ar
CC=aarch64-linux-android21-clang
CXX=aarch64-linux-android21-clang++
AS=$CC
LD=/root/android-ndk-r21/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/aarch64-linux-android/bin/ld
RANLIB=/root/android-ndk-r21/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/aarch64-linux-android/bin/ranlib
STRIP=/root/android-ndk-r21/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/aarch64-linux-android/bin/strip

Configuration (profile_build):
[settings]
arch=x86_64
arch_build=x86_64
build_type=Release
compiler=gcc
compiler.libcxx=libstdc++11
compiler.version=9
os=Linux
os_build=Linux
[options]
[build_requires]
[env]

hello/0.1: Forced build from source
Installing package: hello/0.1
Requirements
    hello/0.1 from local cache - Cache
Packages
    hello/0.1:a2ccebaee30b07c93935ff3643d57c8239e9ee4f - Build

Cross-build from 'Linux:x86_64' to 'Android:armv8'
Installing (downloading, building) binaries...
hello/0.1: Copying sources to build folder
hello/0.1: Building your package in /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f
hello/0.1: Generator txt created conanbuildinfo.txt
hello/0.1: Calling generate()
hello/0.1: Preset 'release' added to CMakePresets.json. Invoke it manually using 'cmake --preset release'
hello/0.1: If your CMake version is not compatible with CMakePresets (<3.19) call cmake like: 'cmake <path> -G "Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE=/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release/generators/conan_toolchain.cmake -DCMAKE_POLICY_DEFAULT_CMP0091=NEW -DCMAKE_BUILD_TYPE=Release'
hello/0.1: Aggregating env generators
hello/0.1: Calling build()
hello/0.1: CMake command: cmake -G "Unix Makefiles" -DCMAKE_TOOLCHAIN_FILE="/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release/generators/conan_toolchain.cmake" -DCMAKE_INSTALL_PREFIX="/root/.conan/data/hello/0.1/_/_/package/a2ccebaee30b07c93935ff3643d57c8239e9ee4f" -DCMAKE_POLICY_DEFAULT_CMP0091="NEW" -DCMAKE_BUILD_TYPE="Release" "/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/."
Re-run cmake no build system arguments
-- Using Conan toolchain: /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release/generators/conan_toolchain.cmake
-- Conan toolchain: Setting CMAKE_POSITION_INDEPENDENT_CODE=ON (options.fPIC)
-- Conan toolchain: Setting BUILD_SHARED_LIBS = OFF
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /root/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release
hello/0.1: CMake command: cmake --build "/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release" '--' '-j12'
/usr/local/bin/cmake -S/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f -B/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release --check-build-system CMakeFiles/Makefile.cmake 0
/usr/local/bin/cmake -E cmake_progress_start /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release/CMakeFiles /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release//CMakeFiles/progress.marks
/usr/bin/make  -f CMakeFiles/Makefile2 all
make[1]: Entering directory '/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release'
/usr/bin/make  -f CMakeFiles/hello.dir/build.make CMakeFiles/hello.dir/depend
make[2]: Entering directory '/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release'
cd /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release && /usr/local/bin/cmake -E cmake_depends "Unix Makefiles" /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release/CMakeFiles/hello.dir/DependInfo.cmake --color=
make[2]: Leaving directory '/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release'
/usr/bin/make  -f CMakeFiles/hello.dir/build.make CMakeFiles/hello.dir/build
make[2]: Entering directory '/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release'
[ 50%] Building CXX object CMakeFiles/hello.dir/src/hello.cpp.o
/root/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/bin/clang++ --target=aarch64-none-linux-android21 --gcc-toolchain=/root/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64 --sysroot=/root/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/sysroot  -I/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/include -g -DANDROID -fdata-sections -ffunction-sections -funwind-tables -fstack-protector-strong -no-canonical-prefixes -D_FORTIFY_SOURCE=2 -Wformat -Werror=format-security   -O2 -DNDEBUG  -fPIC -MD -MT CMakeFiles/hello.dir/src/hello.cpp.o -MF CMakeFiles/hello.dir/src/hello.cpp.o.d -o CMakeFiles/hello.dir/src/hello.cpp.o -c /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/src/hello.cpp
[100%] Linking CXX static library libhello.a
/usr/local/bin/cmake -P CMakeFiles/hello.dir/cmake_clean_target.cmake
/usr/local/bin/cmake -E cmake_link_script CMakeFiles/hello.dir/link.txt --verbose=1
/root/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-ar qc libhello.a CMakeFiles/hello.dir/src/hello.cpp.o
/root/android-ndk-r21/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-ranlib libhello.a
make[2]: Leaving directory '/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release'
[100%] Built target hello
make[1]: Leaving directory '/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release'
/usr/local/bin/cmake -E cmake_progress_start /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release/CMakeFiles 0
hello/0.1: Package 'a2ccebaee30b07c93935ff3643d57c8239e9ee4f' built
hello/0.1: Build folder /root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release
hello/0.1: Generated conaninfo.txt
hello/0.1: Generated conanbuildinfo.txt
hello/0.1: Generating the package
hello/0.1: Package folder /root/.conan/data/hello/0.1/_/_/package/a2ccebaee30b07c93935ff3643d57c8239e9ee4f
hello/0.1: Calling package()
hello/0.1: CMake command: cmake --install "/root/.conan/data/hello/0.1/_/_/build/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/build/Release" --prefix "/root/.conan/data/hello/0.1/_/_/package/a2ccebaee30b07c93935ff3643d57c8239e9ee4f"
-- Install configuration: "Release"
-- Installing: /root/.conan/data/hello/0.1/_/_/package/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/lib/libhello.a
-- Installing: /root/.conan/data/hello/0.1/_/_/package/a2ccebaee30b07c93935ff3643d57c8239e9ee4f/include/hello.h
hello/0.1 package(): Packaged 1 '.h' file: hello.h
hello/0.1 package(): Packaged 1 '.a' file: libhello.a
hello/0.1: Package 'a2ccebaee30b07c93935ff3643d57c8239e9ee4f' created
hello/0.1: Created package revision 661594dbd45e7ccf59fb1d6d12e29822

[memsharded]

I see these lines in my output that I miss in yours:

-- Android: Targeting API '21' with architecture 'arm64', ABI 'arm64-v8a', and processor 'aarch64'
-- Android: Selected unified Clang toolchain
-- The CXX compiler identification is Clang 12.0.8

Not sure why. Next step is to test in Linux, but I would need to setup that I don't have that installed, it can be a bit more challenging.

[cocoza4]

@memsharded thanks for your response, let me know if you need additional information.

[jcar87]

Hi @cocoza4 - I have been able to reproduce this issue.

The cmake toolchain included in the Android NDK (/root/android-ndk-r21/build/cmake/android.toolchain.cmake), which is in turn included by the conan-generated conan_toolchain.cmake, seems to have some unfortunate logic that overrides the values of CMAKE_CXX_FLAGS, so they are not propagated.

We follow the advice by the CMake maintainers (link here) of setting CMAKE_CXX_FLAGS_INIT in the toolchain file, rather than meddle with CMAKE_CXX_FLAGS directly.

The android-ndk provided toolchain on the other had modifies CMAKE_CXX_FLAGS directly in a way that does away with our values. This has been fixed in newer versions of the Android NDK, however I believe even on recent versions it uses the legacy behaviour due to developers relying on the ability to pass CMAKE_CXX_FLAGS to cmake directly.

I have had luck with:

• using the Android r25c NDK
• explicitly passing ANDROID_USE_LEGACY_TOOLCHAIN_FILE to OFF (in the recipe's generate() method, pass it as a cache_variable to the cmaketoolchain object).

Then I see the behaviour you expect. Do you have the ability to use a newer Android NDK while still targeting Android 21?

[cocoza4]

@jcar87 @memsharded thank you very much, I've fixed the issue as you suggested.

[memsharded]

@jcar87 I am re-opening, to discuss if we should add ANDROID_USE_LEGACY_TOOLCHAIN_FILE to OFF automatically in our toolchain, it is possible that this will also impact other users?

[memsharded]

Implemented in #13459, for next 2.0.3

Adding a new conf to opt-in into this Android CMake toolchain behavior is the best we can do, it is a bit of a mess there with the injection of flags, there is not much Conan can do about it.