15. compile Qt for android in Windows Environment

for more infomation,please visit https://doc.qt.io/qt-5/android-building.html

15.1. Prepare

To build Qt for Android under a Windows environment, follow the steps below:

Preparing the Build Environment
Install the following:

A JDK package such as AdoptOpenJDK, JDK, or OpenJDK.
MinGW 7.3 toolchain
Perl

Then set the respective environment variables from the Environment Variables system UI, or from the build command line prompt. For the default Command prompt:

set JDK_ROOT=\bin
set MINGW_ROOT=\bin
set PERL_ROOT=\bin
set PATH=%MINGW_ROOT%;%PERL_ROOT%;%JDK_ROOT%:%PATH%

Then, in the command line prompt, verify that:

where gcc.exe
The command should list gcc.exe under the path <MINGW_ROOT> first.

where mingw32-make.exe
The command should list mingw32-make.exe under the path <MINGW_ROOT> first.

where javac.exe
The command should list javac.exe under the path <JDK_ROOT> first.

Note: JDK 11 or earlier must be used to properly build Qt for Android.
Note: Qt for Android does not support building with Microsoft Visual C++ (MSVC), we only support building with MinGW.
If you have downloaded the source code archive from Qt Downloads, then unpack the archive if you have not done so already. qt-everywhere-src-%VERSION%.tar.xz package

15.2. Compile

save the following compile script into file *.bat
open cmd console,open the source code path,
run the *.bat created in step 1;

compile script

:::::::::::::::::::::::::::::::::::::compile script ::::::::::::::::::::::::::::::::::::
:::::::::::::::::::::::::::::::::::::arm64-v8a  armeabi-v7a  armeabi::::::::::::::::::::

@echo %PATH%

set "ANDROID_API_VERSION=android-21"
set "ANDROID_SDK_ROOT=D:\android\program\adt\sdk"
set "ANDROID_TARGET_ARCH=arm64-v8a"
set "ANDROID_BUILD_TOOLS_REVISION=21.1.2"
set "ANDROID_NDK_PATH=D:\android\program\adt\ndk-r20b"
set "ANDROID_TOOLCHAIN_VERSION=4.9"
set "ANDROID_NDK_HOST=windows-x86_64"
set "BUILD_PATH=E:\Qt\build"
set "PREFIX_PATH=E:\Qt\install"

set JDK_ROOT=D:\Pragram\Java\jdk1.8.0_162\bin
set MINGW_ROOT=E:\SoftWare\mingw32\bin
set PERL_ROOT=C:\Strawberry\perl\bin
set PATH=%MINGW_ROOT%;%PERL_ROOT%;%JDK_ROOT%:%PATH%

::configure.bat -prefix F:\Qt\build -platform win32-g++ -opengl es2 -xplatform android-g++ -android-ndk %ANDROID_NDK_PATH% -android-sdk %ANDROID_SDK_ROOT% -android-toolchain-version 4.9 -nomake tests -nomake examples
::configure.bat  -developer-build -platform win32-g++ -opengl dynamic -xplatform android-g++ -android-ndk %ANDROID_NDK_PATH% -android-sdk %ANDROID_SDK_ROOT% -android-toolchain-version 4.9 -nomake tests -nomake examples

::configure.bat -platform win32-g++ -opengl es2 -xplatform android-g++ -android-ndk %ANDROID_NDK_PATH% -android-sdk %ANDROID_SDK_ROOT% -android-toolchain-version 4.9 -android-ndk-host windows-x86_64 -android-ndk-platform android-21 -opensource -confirm-license -nomake tests -nomake examples -static
::configure.bat -opengl dynamic -no-opengl

pause

mkdir %BUILD_PATH%
mkdir %PREFIX_PATH%
mkdir %BUILD_PATH%\%ANDROID_TARGET_ARCH%
mkdir %PREFIX_PATH%\%ANDROID_TARGET_ARCH%
cd %BUILD_PATH%\%ANDROID_TARGET_ARCH%

..\..\5.12.5\configure.bat -platform win32-g++ -opengl es2 -xplatform android-clang -android-ndk %ANDROID_NDK_PATH% -android-sdk %ANDROID_SDK_ROOT% -android-toolchain-version 4.9 -android-ndk-host windows-x86_64 -android-ndk-platform android-21 -prefix %PREFIX_PATH%\%ANDROID_TARGET_ARCH% -opensource -confirm-license -nomake tests -nomake examples -shared

::mingw32-make -j4
mingw32-make

pause
:::::::::::::::::::::::::::::::::::::compile script::::::::::::::::::::::::::::::::::::

15.3 some problems

Android linker: undefined reference to bsd_signal

/android/ndk/platforms/android-9/arch-arm/usr/include/signal.h:113: error: undefined reference to ‘bsd_signal’

Till android-19 inclusive NDK-s signal.h declared bsd_signal extern and signal was an inline calling bsd_signal.

Starting with android-21 signal is an extern and bsd_signal is not declared at all.

What’s interesting, bsd_signal was still available as a symbol in NDK r10e android-21 libc.so (so there were no linking errors if using r10e), but is not available in NDK r11 and up.

Removing of bsd_signal from NDK-s android-21+ libc.so results in linking errors if code built with android-21+ is linked with static libs built with lower NDK levels that call signal or bsd_signal. Most popular library which calls signal is OpenSSL.

WARNING: Building those static libs with android-21+ (which would put signal symbol directly) would link fine, but would result in *.so failing to load on older Android OS devices due to signal symbol not found in theirs libc.so.

Therefore it’s better to stick with <=android-19 for any code that calls signal or bsd_signal.

To link a library built with android-21 I ended up declaring a bsd_signal wrapper which would call bsd_signal from libc.so (it’s still available in device’s libc.so, even up to Android 7.0).

#if (__ANDROID_API__ > 19)
#include <android/api-level.h>
#include <android/log.h>
#include <signal.h>
#include <dlfcn.h>

extern "C" {
  typedef __sighandler_t (*bsd_signal_func_t)(int, __sighandler_t);
  bsd_signal_func_t bsd_signal_func = NULL;

  __sighandler_t bsd_signal(int s, __sighandler_t f) {
    if (bsd_signal_func == NULL) {
      // For now (up to Android 7.0) this is always available 
      bsd_signal_func = (bsd_signal_func_t) dlsym(RTLD_DEFAULT, "bsd_signal");

      if (bsd_signal_func == NULL) {
        // You may try dlsym(RTLD_DEFAULT, "signal") or dlsym(RTLD_NEXT, "signal") here
        // Make sure you add a comment here in StackOverflow
        // if you find a device that doesn't have "bsd_signal" in its libc.so!!!

        __android_log_assert("", "bsd_signal_wrapper", "bsd_signal symbol not found!");
      }
    }

    return bsd_signal_func(s, f);
  }
}
#endif

PS. Looks like the bsd_signal symbol will be brought back to libc.so in NDK r13:
for more information ,please visit