win7+mingw+android ndk

[luwang-epic]

I am going to compile openblas for android in windows 7. To make in windows 7, I install mingw and msys.
I followed https://github.com/xianyi/OpenBLAS/wiki/How-to-build-OpenBLAS-for-Android to build armv8 with clang.
I

export NDK_BUNDLE_DIR=D:\\software\\android-ndk-r16b
export PATH=$PATH:${NDK_BUNDLE_DIR}\\my-android-toolchain\\bin
export LDFLAGS="-L${NDK_BUNDLE_DIR}\\my-android-toolchain\\lib\\gcc\\aarch64-linux-android\\4.9.x -lm" 
export CLANG_FLAGS="-target aarch64-linux-android --sysroot ${NDK_BUNDLE_DIR}\\my-android-toolchain\\sysroot\\usr\\include -gcc-toolchain ${NDK_BUNDLE_DIR}\\my-android-toolchain\\bin"
make TARGET=ARMV8 AR=ar CC="clang ${CLANG_FLAGS}" NOFORTRAN=1 NO_LAPACK=1 HOSTCC=gcc

Error happened:

stdio.h is in D:\software\android-ndk-r16b\my-android-toolchain\sysroot\usr\include
I included it in CLANG_FLAGS， why this happened?

[martin-frbg]

Does it work when you set sysroot to D:\software\android-ndk-r16b\my-android-toolchain\sysroot,
without the usr\include (and also define the gcc-toolchain without the \bin at the end) ?

[luwang-epic]

I tried ,and new error occured:

$ make TARGET=ARMV8 AR=ar CC="clang ${CLANG_FLAGS}" ONLY_CBLAS=1 HOSTCC=gcc
ln: creating symbolic link `libopenblas.a' to `libopenblas_armv8p-r0.3.0.dev.a':
 No such file or directory
make: [libs] Error 1 (ignored)
d:\software\Mingw\bin\ar.exe: creating ../libopenblas_armv8p-r0.3.0.dev.a
d:\software\android-ndk-r16b\my-android-toolchain\bin\aarch64-linux-android-ld:
cannot find crtbegin_dynamic.o: No such file or directory
d:\software\android-ndk-r16b\my-android-toolchain\bin\aarch64-linux-android-ld:
cannot find -lm
d:\software\android-ndk-r16b\my-android-toolchain\bin\aarch64-linux-android-ld:
cannot find -lgcc
d:\software\android-ndk-r16b\my-android-toolchain\bin\aarch64-linux-android-ld:
cannot find -ldl
d:\software\android-ndk-r16b\my-android-toolchain\bin\aarch64-linux-android-ld:
cannot find -lc
d:\software\android-ndk-r16b\my-android-toolchain\bin\aarch64-linux-android-ld:
cannot find -lgcc
d:\software\android-ndk-r16b\my-android-toolchain\bin\aarch64-linux-android-ld:
cannot find -ldl
d:\software\android-ndk-r16b\my-android-toolchain\bin\aarch64-linux-android-ld:
cannot find crtend_android.o: No such file or directory
clang50.exe: error: linker command failed with exit code 1 (use -v to see invoca
tion)
make[1]: *** [../libopenblas_armv8p-r0.3.0.dev.so] Error 1
make: *** [shared] Error 2

[martin-frbg]

From #1632 (comment) this may actually have been a bug in NDK r16b

[danielcjacobs]

I get this same error trying to build on Fedora 34 with NDK r21e and current OpenBLAS version (0.3.19 I believe)

[martin-frbg]

can you try with the current ndk (23b I believe), just in case this was a temporary regression ?

[danielcjacobs]

Yeah, the paths are a bit different for 23b, so I'm trying to make sure I have them correct. 23b doesn't seem to have all the binaries that the previous versions have (e.g. seems to have removed aarch64-linux-android-strip, aarch64-linux-android-ar, aarch64-linux-android-ld, and aarch64-linux-android-ranlib). I don't see these in the r24 beta either.

[danielcjacobs]

Also, versions after r22b don't seem to have libgcc. Not sure if this means I need to point LDFLAGS somewhere else, or if this will prevent compiling OpenBLAS for Android.

EDIT confirmed, r23 and up do not include libgcc

[danielcjacobs]

can you try with the current ndk (23b I believe), just in case this was a temporary regression ?

Tried with r22b and got same error.
Also of note is that the sysroot path for 22b was different from 21e, and 21e also differed from the instructions.

[danielcjacobs]

Actually, I am getting a slightly different error with versions before 23b:

/home/djacobs/Android/Sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-ld: cannot find crtbegin_so.o: No such file or directory
/home/djacobs/Android/Sdk/ndk/21.4.7075529/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android-ld: cannot find crtend_so.o: No such file or directory

Here's what I'm running:

export NDK_BUNDLE_DIR=/home/djacobs/Android/Sdk/ndk/21.4.7075529
export PATH=${NDK_BUNDLE_DIR}/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin:${NDK_BUNDLE_DIR}/toolchains/llvm/prebuilt/linux-x86_64/bin:$PATH
export LDFLAGS="-L${NDK_BUNDLE_DIR}/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/lib/gcc/aarch64-linux-android/4.9.x -lm"
export CLANG_FLAGS="-target aarch64-linux-android --sysroot ${NDK_BUNDLE_DIR}/sysroot -gcc-toolchain ${NDK_BUNDLE_DIR}/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/"

make TARGET=ARMV8 ONLY_CBLAS=1 AR=ar CC="clang ${CLANG_FLAGS}" HOSTCC=gcc -j4

[martin-frbg]

I have now gotten in to compile with r23b on Fedora34 using just

export PATH=/opt/android-ndk-r23b/toolchains/llvm/prebuilt/linux-x86_64/bin/:$PATH
make HOSTCC=gcc CC=/opt/android-ndk-r23b/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android31-clang ONLY_CBLAS=1 TARGET=ARMV8

can you check if that works for you ? (If you need LAPACK, things will get more complicated due to the current lack of a usable Fortran compiler in the NDK (and in current LLVM in general).

[danielcjacobs]

Wow, that's very simple and works, thanks! I now see #2005 which probably would've helped me had I looked at the closed issues sooner.

Is ONLY_CBLAS=1 the flag that excludes Fortran? And how is this different from setting NOFORTRAN=1

[martin-frbg]

ONLY_CBLAS and NOFORTRAN should be identical, just different origins. And the wiki usually carries the collected wisdom from closed tickets, though Android NDK is a bit of a moving target