Can't build on Ubuntu/Debian with NDK 16

[stoically]

Hi,

thanks for your work on orbot/tor-android!

Tested on Ubuntu 16.04.3 LTS (4.4.0-103-generic x86_x64) and Debian 9 (4.9.0-4-amd64 x86_64)
Android Studio Version: 3.0.1
Android NDK Version: 16.1.4479499
Android SDK Platform Tools Version: 27.0.0
Android SDK Tools: 26.1.1
Installed APIs: 16, 23, 27
Installed packages: ant autotools-dev automake autogen autoconf libtool gettext-base autopoint

When running APP_ABI=armeabi make -C external or APP_ABI=x86 make -C external compiling of xz fails with the error

ISO C99... unsupported
configure: error: No C99 compiler was found.

When removing lzma (xz) it will fail while compiling zstd with the error

In file included from common/entropy_common.c:38:0:
common/mem.h:22:37: fatal error: string.h: No such file or directory
 #include <string.h>     /* memcpy */

When removing zstd it will fail while compiling openssl with the error

In file included from cryptlib.c:117:0:
cryptlib.h:62:21: fatal error: stdlib.h: No such file or directory
 # include <stdlib.h>

I was able to get xz, zstd and openssl to compile correctly by making my own NDK toolchains

$ANDROID_NDK_HOME/build/tools/make-standalone-toolchain.sh --platform=android-16 --install-dir=./external/android-16-arch-arm-toolchain --arch=arm
$ANDROID_NDK_HOME/build/tools/make-standalone-toolchain.sh --platform=android-16 --install-dir=./external/android-16-arch-x86-toolchain --arch=x86

and instructing the Makefile to use them by replacing

NDK_SYSROOT=[..]

with

NDK_TOOLCHAIN_CUSTOM=$(EXTERNAL_ROOT)/android-$(NDK_PLATFORM_LEVEL)-arch-$(NDK_ABI)-toolchain
NDK_SYSROOT=$(NDK_TOOLCHAIN_CUSTOM)/sysroot

and

NDK_TOOLCHAIN_BASE=[..]

with

NDK_TOOLCHAIN_BASE=$(NDK_TOOLCHAIN_CUSTOM)

However then configuring of Tor fails with the error

checking for libevent directory... configure: WARNING: Could not find a linkable libevent.  If you have it installed somewhere unusual, you can specify an explicit path using --with-libevent-dir

The external/lib directory exists and contains the libevent.a file. I'm not sure how to debug this further so any help would be appreciated. If I can provide more informations please let me know.

Best regards

[stoically]

So I checked the Issues over at n8fr8/orbot and saw that orbot relies on ndk 10e. Tried building again with ndk 10e and it works just fine.

Maybe it would be nice to have a hint somewhere pointing that out in the BUILDING file? Anyway, it's solved for me so I'm closing this.

[goapunk]

Sorry for the hassle. I agree it should be indicated in BUILD. @n8fr8 is there any special reason why you don't use the lastest ndk ? :)