Build error because of "implicit declaration of function 'sendfile'"

[Marc Richter]

Subj: Build error because of "implicit declaration of function 'sendfile'"

Hi everyone,

I'm a first-time user of Kivy and Buildozer and my goal is to build a Python App for Android. I created an Android AVD Orio (8.1, API 27) emulator for x86.
Next, I created an empty folder named `buildozer`, switched to it and executed `buildozer init`, which created a file named buildozer.spec. In that file, I only changed `android.arch`from `armeabi-v7a` to `x86` and left the rest as is.

I then took a code example from https://realpython.com/mobile-app-kivy-python/#creating-a-kivy-application and saved that as `main.py` in the `buildozer/` directory.
On the commandline, I changed into that buildozer/ directory and executed `buildozer -v android debug` with the virtualenv activated.
This results in this:


gcc -c -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -I/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy1/buildozer/.buildozer/android/platform/build-x86/build/other_builds/hostpython3/desktop/hostpython3/Include/internal -IObjects -IInclude -IPython -I. -I/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy1/buildozer/.buildozer/android/platform/build-x86/build/other_builds/hostpython3/desktop/hostpython3/Include -I/usr/local/opt/zlib/include -I/usr/local/opt/bzip2/include -I/usr/local/opt/zlib/include -I/usr/local/opt/bzip2/include -DPy_BUILD_CORE -o Programs/_testembed.o /Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy1/buildozer/.buildozer/android/platform/build-x86/build/other_builds/hostpython3/desktop/hostpython3/Programs/_testembed.c
sed -e "s,@EXENAME@,/usr/local/bin/python3.8," < /Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy1/buildozer/.buildozer/android/platform/build-x86/build/other_builds/hostpython3/desktop/hostpython3/Misc/python-config.in >python-config.py
/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy1/buildozer/.buildozer/android/platform/build-x86/build/other_builds/hostpython3/desktop/hostpython3/Modules/posixmodule.c:9084:15: error:
implicit declaration of function 'sendfile' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
ret = sendfile(in, out, offset, &sbytes, &sf, flags);
^
LC_ALL=C sed -e 's,\$(\([A-Za-z0-9_]*\)),\$\{\1\},g' < Misc/python-config.sh >python-config
1 error generated.
make: *** [Modules/posixmodule.o] Error 1


Since I'm a first-time user of Kivy and Buildozer, I do not have any clue what's going on.
Can someone please provide me some jump start?

Best regards,
Marc Richter

[planckp...@gmail.com]

No clue here either.

It looks like an install issue, but I really don't know, check all the install steps were followed:

https://buildozer.readthedocs.io/en/latest/installation.html#android-on-ubuntu-20-04-64bit

Best to start with Kivy docs, Hello World, https://kivy.org/doc/stable/guide/basic.html#create-an-application

[Marc Richter]

I once more followed all guides to install Kivy using 

• Homebrew Python 3.8.6
• a virtualenv inside the project folder (was a pipenv using Python 3.8.6 installed by pyenv before)
• `kivy[full]`, `cython` and `kivy_examples` using pip

Also, I followed these guides to setup my MacOSX Environment:

• https://buildozer.readthedocs.io/en/latest/installation.html#android-on-ubuntu-20-04-64bit
  
• https://kivy.org/doc/stable/gettingstarted/installation.html#install-pip
  

Afterward, I could run the minimal example in Create an application and `kivy-examples/demo/showcase/main.py` fine.

Heading back to my Real Python article at https://realpython.com/mobile-app-kivy-python/#creating-a-kivy-application, the full code example of the calculator also runs fine in my MacOSX environment. That's 3 code samples, that are satisfied with my Kivy environment setup in MacOSX.

The next step is to follow the `buildozer` - section to build an Android package out of the calculator app.

I did this step-by-step wise as follows:

1. mkdir buildozer && cd buildozer
   
2. buildozer init
   
3. cp ../calculator.py ./main.py
   
4. buildozer -v android debug
   

Unce more, with this result:

gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall    -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration  -I/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer/.buildozer/android/platform/build-armeabi-v7a/build/other_builds/hostpython3/desktop/hostpython3/Include/internal -IObjects -IInclude -IPython -I. -I/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer/.buildozer/android/platform/build-armeabi-v7a/build/other_builds/hostpython3/desktop/hostpython3/Include -I/usr/local/opt/zlib/include -I/usr/local/opt/bzip2/include -I/usr/local/opt/zlib/include -I/usr/local/opt/bzip2/include  -DPy_BUILD_CORE_BUILTIN  -DPy_BUILD_CORE_BUILTIN -I/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer/.buildozer/android/platform/build-armeabi-v7a/build/other_builds/hostpython3/desktop/hostpython3/Include/internal -c /Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer/.buildozer/android/platform/build-armeabi-v7a/build/other_builds/hostpython3/desktop/hostpython3/Modules/_functoolsmodule.c -o Modules/_functoolsmodule.o

/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer/.buildozer/android/platform/build-armeabi-v7a/build/other_builds/hostpython3/desktop/hostpython3/Modules/posixmodule.c:9084:15: error: 

      implicit declaration of function 'sendfile' is invalid in C99 [-Werror,-Wimplicit-function-declaration]

        ret = sendfile(in, out, offset, &sbytes, &sf, flags);

              ^

gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -DNDEBUG -g -fwrapv -O3 -Wall    -std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration  -I/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer/.buildozer/android/platform/build-armeabi-v7a/build/other_builds/hostpython3/desktop/hostpython3/Include/internal -IObjects -IInclude -IPython -I. -I/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer/.buildozer/android/platform/build-armeabi-v7a/build/other_builds/hostpython3/desktop/hostpython3/Include -I/usr/local/opt/zlib/include -I/usr/local/opt/bzip2/include -I/usr/local/opt/zlib/include -I/usr/local/opt/bzip2/include  -DPy_BUILD_CORE_BUILTIN  -c /Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer/.buildozer/android/platform/build-armeabi-v7a/build/other_builds/hostpython3/desktop/hostpython3/Modules/_operator.c -o Modules/_operator.o

1 error generated.

make: *** [Modules/posixmodule.o] Error 1

make: *** Waiting for unfinished jobs....

1 warning generated.

  STDERR:

# Command failed: /Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/venv/bin/python -m pythonforandroid.toolchain create --dist_name=myapp --bootstrap=sdl2 --requirements=python3,kivy --arch armeabi-v7a --copy-libs --color=always --storage-dir="/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer/.buildozer/android/platform/build-armeabi-v7a" --ndk-api=21

# ENVIRONMENT:

#     SHELL = '/usr/local/bin/bash'

#     PYENV_SHELL = 'bash'

#     XPC_FLAGS = '0x0'

#     CONDA_EXE = '/usr/local/Caskroom/miniconda/base/bin/conda'

#     _CE_M = ''

#     TERMINAL_EMULATOR = 'JetBrains-JediTerm'

#     HISTSIZE = '-1'

#     __CFBundleIdentifier = 'com.jetbrains.pycharm'

#     SSH_AUTH_SOCK = '/private/tmp/com.apple.launchd.3wZrQQagRo/Listeners'

#     BLUE = '\\033[01;34m'

#     PWD = '/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer'

#     PYENV_VIRTUALENV_INIT = '1'

#     LOGNAME = 'marcrichter'

#     CONDA_PREFIX = '/usr/local/Caskroom/miniconda/base'

#     RESET = '\\033[00m'

#     COMMAND_MODE = 'unix2003'

#     LDFLAGS = '-L/usr/local/opt/zlib/lib -L/usr/local/opt/bzip2/lib'

#     HOME = '/Users/marcrichter'

#     COLUMNS = '193'

#     VIRTUAL_ENV = '/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/venv'

#     CONDA_PROMPT_MODIFIER = '(base) '

#     TMPDIR = '/var/folders/fn/vyh4bf7n1l73k4pfypqdp2tm0000gp/T/'

#     CPPFLAGS = '-I/usr/local/opt/zlib/include -I/usr/local/opt/bzip2/include'

#     ANDROID_AVD_HOME = '/Users/marcrichter/.android/avd'

#     ANDROID_HOME = '/Users/marcrichter/Library/Android/sdk'

#     TERM = 'xterm-256color'

#     _CE_CONDA = ''

#     USER = 'marcrichter'

#     OBJC_DISABLE_INITIALIZE_FORK_SAFETY = 'YES'

#     CONDA_SHLVL = '1'

#     DISPLAY = '/private/tmp/com.apple.launchd.MEle43ZjeF/org.macosforge.xquartz:0'

#     SHLVL = '1'

#     ANDROID_SDK_ROOT = '/Users/marcrichter/Library/Android/sdk'

#     XPC_SERVICE_NAME = '0'

#     CONDA_PYTHON_EXE = '/usr/local/Caskroom/miniconda/base/bin/python'

#     LC_CTYPE = 'en_DE.UTF-8'

#     RED = '\\033[1;31m'

#     PS1 = ('(venv) (base) [last: ${timer_show}] [exit: `nonzero_return`] '

 '\\033[01;34m\\u\\033[00m \\D{%H:%M:%S (%Z) %a '

 '%Y-%m-%d}\\n\\033[01;34m`pwd`\\033[00m\\n\\W \\$ ')

#     CONDA_DEFAULT_ENV = 'base'

#     LC_ALL = 'en_US.utf-8'

#     PATH = ('/Users/marcrichter/.buildozer/android/platform/apache-ant-1.9.4/bin:/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/venv/bin:/usr/local/opt/openssl@1.1/bin:/usr/local/opt/curl/bin:/usr/local/opt/sqlite/bin:/usr/local/Caskroom/miniconda/base/bin:/usr/local/Caskroom/miniconda/base/condabin:/usr/local/Caskroom/google-cloud-sdk/latest/google-cloud-sdk/bin:/Library/Frameworks/Python.framework/Versions/3.7/bin:/usr/local/bin:/Users/marcrichter/.pyenv/plugins/pyenv-virtualenv/shims:/Users/marcrichter/.pyenv/shims:/Users/marcrichter/.pyenv/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/MacGPG2/bin:/usr/local/share/dotnet:/usr/local/munki:/opt/X11/bin:~/.dotnet/tools:/Library/Apple/usr/bin:/Library/Frameworks/Mono.framework/Versions/Current/Commands:/Applications/Xamarin '

 'Workbooks.app/Contents/SharedSupport/path-bin')

#     GREEN = '\\033[01;32m'

#     HISTFILESIZE = '-1'

#     OLDPWD = '/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2'

#     __CF_USER_TEXT_ENCODING = '0x1F6:0x0:0x0'

#     _ = '/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/venv/bin/buildozer'

#     PACKAGES_PATH = '/Users/marcrichter/.buildozer/android/packages'

#     ANDROIDSDK = '/Users/marcrichter/.buildozer/android/platform/android-sdk'

#     ANDROIDNDK = '/Users/marcrichter/.buildozer/android/platform/android-ndk-r19c'

#     ANDROIDAPI = '27'

#     ANDROIDMINAPI = '21'

# 

# Buildozer failed to execute the last command

# The error might be hidden in the log above this error

# Please read the full log, and search for it before

# raising an issue with buildozer itself.

# In case of a bug report, please add a full log with log_level = 2

(venv) (base) [last: 190s] [exit: 1] marcrichter 14:39:30 (CET) Sat 2020-12-12

/Users/marcrichter/ownCloud/Dokumente/Entwicklung/Android/kivy2/buildozer

buildozer $

I'm out of ideas what else in this quite basic setup I could possibly do different.

Any ideas from a more kivy advanced fella?

Best regards,

Marc Richter

[Marc Richter]

Found it!

It is neither an issue in buildozer, nor kivy. It is a Python compilation issue that happens in conjunction with macOS Big Sur; see https://github.com/pyenv/pyenv/issues/1737 for details.

I was able to work around this by doing the following (I did it with python-for-android, but should work similarly with buildozer):

1. run `p4a apk` (or `buildozer -v android debug`) and wait until the shown error occurs.
2. Apply the patch https://github.com/python/cpython/commit/8ea6353.patch/?full_index\=1 to the source folder where p4a / buildozer compile Python in so that `configure` and `configure.ac` files are changed; should be:
   1. p4a: ~/.python-for-android/build/other_builds/hostpython3/desktop/hostpython3/
   2. buildozer: ${YOUR_BUILD_DIR}/.buildozer/android/platform/build-armeabi-v7a/build/other_builds/hostpython3/desktop/hostpython3/

That should be it!

I now have a different problem, but this should be the fix for the initial problem.

Now I face:

checking for arm-linux-androideabi-gcc... /Users/marcrichter/.buildozer/android/platform/android-ndk-r19c/toolchains/llvm/prebuilt/darwin-x86_64/bin/armv7a-linux-androideabi21-clang

checking whether the C compiler works... no

configure: error: in `/Users/marcrichter/.python-for-android/build/other_builds/python3/armeabi-v7a__ndk_target_21/python3/android-build':

configure: error: C compiler cannot create executables

But that's another story :)

Best regards,

Marc Richter

[Leo BigSure]

Hi!

I opened a issues in buildozer repo:

https://github.com/kivy/buildozer/issues/1262

[Raghav]

Thank you for the solution! It worked flawlessly.

For your next error with "configure: error: C compiler cannot create executables", try enabling altering your security setting in mac to enable it to "Allow apps from anywhere". Refer this link for same: https://www.macworld.co.uk/how-to/mac-app-unidentified-developer-3669596/

Although, after passing through this error, now I'm stuck at a new error that reads:

sh.ErrorReturnCode_1:


  RAN: /Users/raghav/.python-for-android/build/other_builds/hostpython3/desktop/hostpython3/native-build/python3 -m venv venv


  STDOUT:
Error: Command '['/Users/raghav/.python-for-android/build/venv/bin/python3', '-Im', 'ensurepip', '--upgrade', '--default-pip']' returned non-zero exit status 1.




  STDERR:

Could you help me solve this?