Building OpenCV 4.0 for Android: Cannot Include <iostream>?

Issue

I am trying to build OpenCV from source for Android library. However, the following error occurs:

[ 18%] Building C object 3rdparty/libtiff/CMakeFiles/libtiff.dir/tif_unix.c.o
/mnt/d/OpenCVBuild/src/3rdparty/libtiff/tif_stream.cxx:29:20: fatal error: iostream: No such file or directory
 #include <iostream>

(By the way, such error seems to happen whenever it tries to include iostream, and I just paste one typical error since everyone is same.)

My build command:

/mnt/d/OpenCVBuild/cmake-3.15.1-Linux-x86_64/bin/cmake \
-DCMAKE_TOOLCHAIN_FILE=../src/platforms/android/android.toolchain.cmake \
-DANDROID_ABI=arm64-v8a \
-DANDROID_STL=c++_shared \
-DCMAKE_ANDROID_STL_TYPE=c++_shared \
-DANDROID_NATIVE_API_LEVEL=27 \
-DANDROID_SDK=/mnt/d/OpenCVBuild/android-sdk \
-DANDROID_NDK=/mnt/d/OpenCVBuild/android-ndk-r16b-linux-x86_64 \
-DCMAKE_BUILD_TYPE=Release \
-DBUILD_SHARED_LIBS=ON \
-DBUILD_FAT_JAVA_LIB=OFF \
-DBUILD_PROTOBUF=OFF \
-DWITH_CUDA=OFF -DWITH_MATLAB=OFF -DBUILD_ANDROID_PROJECTS=OFF -DBUILD_ANDROID_EXAMPLES=OFF -DBUILD_DOCS=OFF -DBUILD_PERF_TESTS=OFF -DBUILD_TESTS=OFF \
../src \
&& make -j4

Thanks for any advice!!

EDIT: compile with -j1

[ 13%] Building CXX object 3rdparty/libtiff/CMakeFiles/libtiff.dir/tif_stream.cxx.o
/mnt/d/OpenCVBuild/src/3rdparty/libtiff/tif_stream.cxx:29:20: fatal error: iostream: No such file or directory
 #include <iostream>
                    ^
compilation terminated.
3rdparty/libtiff/CMakeFiles/libtiff.dir/build.make:582: recipe for target '3rdparty/libtiff/CMakeFiles/libtiff.dir/tif_stream.cxx.o' failed
make[2]: *** [3rdparty/libtiff/CMakeFiles/libtiff.dir/tif_stream.cxx.o] Error 1
CMakeFiles/Makefile2:293: recipe for target '3rdparty/libtiff/CMakeFiles/libtiff.dir/all' failed
make[1]: *** [3rdparty/libtiff/CMakeFiles/libtiff.dir/all] Error 2
Makefile:162: recipe for target 'all' failed
make: *** [all] Error 2

About where is the iostream: in location d:\OpenCVBuild\android-ndk-r16b-linux-x86_64\sources\cxx-stl\llvm-libc++\include\, there a lot of files, including the iostream (however without any extension, not iostream.h).

By the way, this is some info of cmake:

--   CPU/HW features:
--     Baseline:                    NEON
--       requested:                 NEON FP16
--
--   C/C++:
--     Built as dynamic libs?:      YES
--     C++ Compiler:                /mnt/d/OpenCVBuild/android-ndk-r16b-linux-x86_64/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-g++  (ver 4.9.0)
--     C++ flags (Release):         -fexceptions -frtti -Wno-psabi --sysroot=/mnt/d/OpenCVBuild/android-ndk-r16b-linux-x86_64/platforms/android-27/arch-arm64 -funwind-tables -fsigned-char -no-canonical-prefixes -fdata-sections -ffunction-sections -Wa,--noexecstack  -DANDROID -D__ANDROID_API__=27   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wsign-promo -Wuninitialized -Winit-self -Wno-delete-non-virtual-dtor -Wno-comment -Wno-missing-field-initializers -fdiagnostics-show-option -fomit-frame-pointer -ffunction-sections -fdata-sections   -fvisibility=hidden -fvisibility-inlines-hidden -fomit-frame-pointer -fstrict-aliasing -funswitch-loops -finline-limit=300 -O3 -DNDEBUG  -DNDEBUG
--     C++ flags (Debug):           -fexceptions -frtti -Wno-psabi --sysroot=/mnt/d/OpenCVBuild/android-ndk-r16b-linux-x86_64/platforms/android-27/arch-arm64 -funwind-tables -fsigned-char -no-canonical-prefixes -fdata-sections -ffunction-sections -Wa,--noexecstack  -DANDROID -D__ANDROID_API__=27   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wsign-promo -Wuninitialized -Winit-self -Wno-delete-non-virtual-dtor -Wno-comment -Wno-missing-field-initializers -fdiagnostics-show-option -fomit-frame-pointer -ffunction-sections -fdata-sections   -fvisibility=hidden -fvisibility-inlines-hidden -fno-omit-frame-pointer -fno-strict-aliasing -O0 -g -DDEBUG -D_DEBUG  -DDEBUG -D_DEBUG
--     C Compiler:                  /mnt/d/OpenCVBuild/android-ndk-r16b-linux-x86_64/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-gcc
--     C flags (Release):           -fexceptions -Wno-psabi --sysroot=/mnt/d/OpenCVBuild/android-ndk-r16b-linux-x86_64/platforms/android-27/arch-arm64 -funwind-tables -fsigned-char -no-canonical-prefixes -fdata-sections -ffunction-sections -Wa,--noexecstack  -DANDROID -D__ANDROID_API__=27   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wuninitialized -Winit-self -Wno-comment -Wno-missing-field-initializers -fdiagnostics-show-option -fomit-frame-pointer -ffunction-sections -fdata-sections   -fvisibility=hidden -fomit-frame-pointer -fstrict-aliasing -funswitch-loops -finline-limit=300 -O3 -DNDEBUG  -DNDEBUG
--     C flags (Debug):             -fexceptions -Wno-psabi --sysroot=/mnt/d/OpenCVBuild/android-ndk-r16b-linux-x86_64/platforms/android-27/arch-arm64 -funwind-tables -fsigned-char -no-canonical-prefixes -fdata-sections -ffunction-sections -Wa,--noexecstack  -DANDROID -D__ANDROID_API__=27   -fsigned-char -W -Wall -Werror=return-type -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point -Wformat -Werror=format-security -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self -Wpointer-arith -Wuninitialized -Winit-self -Wno-comment -Wno-missing-field-initializers -fdiagnostics-show-option -fomit-frame-pointer -ffunction-sections -fdata-sections   -fvisibility=hidden -fno-omit-frame-pointer -fno-strict-aliasing -O0 -g -DDEBUG -D_DEBUG  -DDEBUG -D_DEBUG
--     Linker flags (Release):      -Wl,--no-undefined -Wl,-allow-shlib-undefined -Wl,--gc-sections -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now   -Wl,--gc-sections
--     Linker flags (Debug):        -Wl,--no-undefined -Wl,-allow-shlib-undefined -Wl,--gc-sections -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now   -Wl,--gc-sections
--     ccache:                      NO
--     Precompiled headers:         NO
--     Extra dependencies:          dl m log

---

EDIT2: I tried to use gnustl, i.e.

-DANDROID_STL=gnustl_static \
-DCMAKE_ANDROID_STL_TYPE=gnustl_static \

but with error:

[ 69%] Building CXX object modules/core/CMakeFiles/opencv_core.dir/src/utils/logtagmanager.cpp.o
/mnt/d/OpenCVBuild/src/modules/core/src/utils/logtagconfigparser.cpp: In static member function 'static std::string cv::utils::logging::LogTagConfigParser::toString(cv::utils::logging::LogLevel)':
/mnt/d/OpenCVBuild/src/modules/core/src/utils/logtagconfigparser.cpp:301:16: error: 'to_string' is not a member of 'std'
         return std::to_string((int)level);
                ^
/mnt/d/OpenCVBuild/src/modules/core/src/utils/logtagconfigparser.cpp:303:1: error: control reaches end of non-void function [-Werror=return-type]
 }

Solution

include <iostream> is available only in C++ language, and not C. Those are different languages (even tough they are very similar).

You code is saved into a C file

[ 18%] Building C object 3rdparty/libtiff/CMakeFiles/libtiff.dir/tif_unix.c.o
/mnt/d/OpenCVBuild/src/3rdparty/libtiff/tif_stream.cxx:29:20: fatal error: 
iostream: No such file or directory
#include <iostream>

Are you including a C++ file into a C file? Please re-run the code with make -j1 to get a proper error (messages will not get interlaced between compilation threads).

Answered By - elcuco