Error when Cross-compiling library for ARMv7l

[locnnil]

I'm trying to cross compile the log4cxx lib for an armv7l arch.

Steps to reproduce:

Install the cross tolchain arm-linux-gnueabi

sudo apt install -y gcc-arm-linux-gnueabi g++-arm-linux-gnueabi binutils-arm-linux-gnueabi

Start some env variables to hold directores

export DIR_TARGET=/data/marthe/usr
export DIR_HOST=$HOME/project/lib/expat

Expat dependency library

wget https://github.com/libexpat/libexpat/releases/download/R_2_5_0/expat-2.5.0.tar.gz
## Extract the source code
tar -xvf expat-2.5.0.tar.gz
cd expat-2.5.0

Configuring

./configure \
--build=i686-pc-linux-gnu \
--host=arm-linux-gnueabi \
--prefix=$DIR_HOST \
--exec-prefix=$DIR_HOST \
STRIP="/usr/bin/arm-linux-gnueabi-strip" \
AR="/usr/bin/arm-linux-gnueabi-ar" \
CC="/usr/bin/arm-linux-gnueabi-gcc -march=armv7-a -mfloat-abi=softfp -mfpu=neon" \
CXX="/usr/bin/arm-linux-gnueabi-g++ -march=armv7-a -mfloat-abi=softfp -mfpu=neon" \
CFLAGS="-O3 -fexpensive-optimizations -frename-registers -fomit-frame-pointer" \
CXXFLAGS="-O3 -fexpensive-optimizations -frename-registers -fomit-frame-pointer" \
LDFLAGS="-Wl,--strip-all -Wl,--rpath=$DIR_TARGET/lib -Wl,--dynamic-linker=$DIR_TARGET/lib/ld-linux.so.3 -Wl,-O3 -Wl,--hash-style=gnu -Wl,--as-needed" \
CPP="/usr/bin/arm-linux-gnueabi-gcc -E -march=armv7-a -mfloat-abi=softfp -mfpu=neon" \
CXXCPP="/usr/bin/arm-linux-gnueabi-g++ -E -march=armv7-a -mfloat-abi=softfp -mfpu=neon" \
STRIP="/usr/bin/arm-linux-gnueabi-strip" \
OBJDUMP="/usr/bin/arm-linux-gnueabi-objdump"

make -j4 

make install

Log4cxx instalation

Downloading and extracting source code

wget https://dlcdn.apache.org/logging/log4cxx/1.0.0/apache-log4cxx-1.0.0.tar.gz
tar -xvf apache-log4cxx-1.0.0.tar.gz
cd  apache-log4cxx-1.0.0

Configuring

cmake -Bbuild -H. \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_INSTALL_PREFIX=$HOME/project/lib/log4cxx \
  -DCMAKE_TOOLCHAIN_FILE=$HOME/project/cmake/toolchain-arm-linux-gnueabi.cmake \
  -DBUILD_TESTING=off \
  -DBUILD_SHARED_LIBS=off \
  -DEXPAT_LIBRARY=$HOME/project/lib/expat/lib \
  -DEXPAT_INCLUDE_DIR=$HOME/project/lib/expat/include \
  -G "Unix Makefiles"

Error from configuration step

-- Available appenders:
--   Async Appender .................. : ON
--   ODBC Appender ................... : OFF
--   SMTP Appender ................... : OFF
--   XMLSocketAppender ............... : ON
--   SocketHubAppender ............... : ON
--   SyslogAppender .................. : ON
--   TelnetAppender .................. : ON
--   NTEventLogAppender .............. : OFF
--   OutputDebugStringAppender ....... : ON
--   ConsoleAppender ................. : ON
--   FileAppender .................... : ON
--   RollingFileAppender ............. : ON
--   MultiprocessRollingFileAppender . : OFF
-- Available layouts:
--   HTMLLayout ...................... : ON
--   JSONLayout ...................... : ON
--   PatternLayout ................... : ON
--   SimpleLayout .................... : ON
--   XMLLayout ....................... : ON
--   FMTLayout ....................... : OFF
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
/home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/APR_INCLUDE_DIR
   used as include directory in directory /home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/main/cpp
/home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/APR_UTIL_INCLUDE_DIR
   used as include directory in directory /home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/main/cpp

-- Configuring incomplete, errors occurred!
See also "/home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/build/CMakeFiles/CMakeOutput.log".
See also "/home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/build/CMakeFiles/CMakeError.log".

these are the log files of the errors:

CMakeError.log
CMakeOutput.log

[rm5248]

Are you using pkgconfig to compile other code and find the libraries? If I remember correctly you need to set the PKG_CONFIG_PATH and/or PKG_CONFIG_SYSROOT_DIR variables(see also this stackoverflow post).

[locnnil]

Currenty to find the libraries and compile the code I'm using the Cmake file toolchain-arm-linux-gnueabi.cmake that points to my toolchain.

This is my toolchain file:

set(CMAKE_SYSTEM_PROCESSOR arm)
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_VERSION 1)

set(cpu_flags "-march=armv7-a -mfloat-abi=softfp -mfpu=neon")
set(c_cxx_flags " -O2 -fexpensive-optimizations -frename-registers -fomit-frame-pointer -pthread")

set(CMAKE_C_COMPILER   /usr/bin/arm-linux-gnueabi-gcc ${cpu_flags})
set(CMAKE_CXX_COMPILER /usr/bin/arm-linux-gnueabi-g++ ${cpu_flags})

set (CMAKE_SHARED_LINKER_FLAGS "-Wl,-start-group -lpthread -lm -Wl,-end-group -Wl,--rpath=${target_dir}/lib -Wl,--dynamic-linker=${target_dir}/lib/ld-linux.so.3 -Wl,-O3 -Wl,--hash-style=gnu -Wl,--as-needed")

set(CMAKE_C_FLAGS ${c_cxx_flags})
set(CMAKE_CXX_FLAGS ${c_cxx_flags})
set(CMAKE_STRIP /usr/bin/arm-linux-gnueabi-strip)
set(CMAKE_FIND_ROOT_PATH  /usr/arm-linux-gnueabi)
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

I realized that my toolchain file was missing the specification -pthread to tell the compiler that I'm going to use the thread library. Also the linker flag -lpthread but this last is only for the linker and don't map the macros inside the library so I had to use both.

But now I'm with a different error. It's a linking error too saying that:

cannot find -lesmtp

So now I'm going to cross compile libESMTP. But first, is this library realy necessary or just used for some feature? If so, is there an Cmake option where I can disable it?

[rm5248]

libESMTP is completely optional.

If it's complaining about that, you likely have it installed on your build system - it is only used if it is found.

The check happens here, perhaps this is not working correctly when cross-compiling.

[swebb2066]

CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
/home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/APR_INCLUDE_DIR
used as include directory in directory /home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/main/cpp
/home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/APR_UTIL_INCLUDE_DIR

You need to build APR and APR-UTIL with your cross-compiler.

To cross-compile APR you will need a triplet file that locates the tool chain and sets --host and --cache parameters of "./configure".
The .cache file must have been generated on the targeted host using "./configure -C".

[swebb2066]

On reflection, I am not sure I ever successfully build APR and APR-UTIL with a cross-compiler.

What I found works is to use the conan package manager (and a Artifactory server from JFrog). This allows APR and APR-UTIL to be built on the native system and uploaded to the server for use in cross-compilation builds.

The conan package manager can be used to install APR and APR-UTIL from the remote Artifactory server.

[locnnil]

libESMTP is completely optional.

If it's complaining about that, you likely have it installed on your build system - it is only used if it is found.

The check happens here, perhaps this is not working correctly when cross-compiling.

So if I just comment this part I will be able to cross-compile successfully? If yes, I'll gonna try it and post here the results.

[rm5248]

So if I just comment this part I will be able to cross-compile successfully? If yes, I'll gonna try it and post here the results.

That seems like a good thing to try.

Okay, I'm going to try this! But just one question, did the ./configure -C compiles something on my environment or just use some coreutils and other simple things? Because my target (which is algo my host) environment it's pretty limited. It's a embedded armv7l running with BusyBox.

I have no idea - I have found cross-compiling is hard to setup correctly. If the build scripts are not setup correctly it may not work. In theory, cross-compiling only checks things in the rootfs(e.g. include files, libraries). You may also need to worry about the --sysroot option for GCC.

[locnnil]

CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
/home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/APR_INCLUDE_DIR
used as include directory in directory /home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/main/cpp
/home/lincoln/cross_compile/source/apache-log4cxx-1.0.0/src/APR_UTIL_INCLUDE_DIR

You need to build APR and APR-UTIL with your cross-compiler.

To cross-compile APR you will need a triplet file that locates the tool chain and sets --host and --cache parameters of "./configure". The .cache file must have been generated on the targeted host using "./configure -C".

Okay, I'm going to try this! But just one question, did the ./configure -C compiles something on my environment or just use some coreutils and other simple things? Because my target (which is also my host) environment it's pretty limited. It's a embedded armv7l running with BusyBox.

[swebb2066]

The autotools ./configure -C does a lot of stuff, including trying to compile some code.

As BusyBox does not support gcc, you will need to hack a cache file generated on some other armv7 machine (say a raspberrypi).

Perhaps you should also look at this old PR

[Zaoui-Douaa]

how can i build log4cxx with linux arm cortex A9

[rm5248]

If you have a specific issue compiling, please create a new issue. Every system is different, but the process of cross-compiling should be similar for all systems.