Documentation for building unit tests for Android

BUG=webm:1258

Change-Id: Iea142f7b0df0e047720e8c5362464932de57d564

2 files changed, 57 insertions, 34 deletions

diff --git a/build/make/Android.mk b/build/make/Android.mk
index 9ccb5da26..36120170e 100644
--- a/build/make/Android.mk
+++ b/build/make/Android.mk
@@ -41,6 +41,25 @@
 # Running ndk-build will build libvpx and include it in your project.
 #
 
+# Alternatively, building the examples and unit tests can be accomplished in the
+# following way:
+#
+# Create a standalone toolchain from the NDK:
+# https://developer.android.com/ndk/guides/standalone_toolchain.html
+#
+# For example - to test on arm64 devices with clang:
+# $NDK/build/tools/make_standalone_toolchain.py \
+#   --arch arm64 --install-dir=/tmp/my-android-toolchain
+# export PATH=/tmp/my-android-toolchain/bin:$PATH
+# CROSS=aarch64-linux-android- CC=clang CXX=clang++ /path/to/libvpx/configure \
+#   --target=arm64-android-gcc
+#
+# Push the resulting binaries to a device and run them:
+# adb push test_libvpx /data/tmp/test_libvpx
+# adb shell /data/tmp/test_libvpx --gtest_filter=\*Sixtap\*
+#
+# Make sure to push the test data as well and set LIBVPX_TEST_DATA
+
 CONFIG_DIR := $(LOCAL_PATH)/
 LIBVPX_PATH := $(LOCAL_PATH)/libvpx
 ASM_CNV_PATH_LOCAL := $(TARGET_ARCH_ABI)/ads2gas
diff --git a/build/make/configure.sh b/build/make/configure.sh
index 14fada09d..35609e89a 100644
--- a/build/make/configure.sh
+++ b/build/make/configure.sh
@@ -978,47 +978,50 @@ EOF
           ;;
 
         android*)
-          if [ -z "${sdk_path}" ]; then
-            die "Must specify --sdk-path for Android builds."
-          fi
-
-          SDK_PATH=${sdk_path}
-          COMPILER_LOCATION=`find "${SDK_PATH}" \
-                             -name "arm-linux-androideabi-gcc*" -print -quit`
-          TOOLCHAIN_PATH=${COMPILER_LOCATION%/*}/arm-linux-androideabi-
-          CC=${TOOLCHAIN_PATH}gcc
-          CXX=${TOOLCHAIN_PATH}g++
-          AR=${TOOLCHAIN_PATH}ar
-          LD=${TOOLCHAIN_PATH}gcc
-          AS=${TOOLCHAIN_PATH}as
-          STRIP=${TOOLCHAIN_PATH}strip
-          NM=${TOOLCHAIN_PATH}nm
-
-          if [ -z "${alt_libc}" ]; then
-            alt_libc=`find "${SDK_PATH}" -name arch-arm -print | \
-              awk '{n = split($0,a,"/"); \
+          if [ -n "${sdk_path}" ]; then
+            SDK_PATH=${sdk_path}
+            COMPILER_LOCATION=`find "${SDK_PATH}" \
+              -name "arm-linux-androideabi-gcc*" -print -quit`
+            TOOLCHAIN_PATH=${COMPILER_LOCATION%/*}/arm-linux-androideabi-
+            CC=${TOOLCHAIN_PATH}gcc
+            CXX=${TOOLCHAIN_PATH}g++
+            AR=${TOOLCHAIN_PATH}ar
+            LD=${TOOLCHAIN_PATH}gcc
+            AS=${TOOLCHAIN_PATH}as
+            STRIP=${TOOLCHAIN_PATH}strip
+            NM=${TOOLCHAIN_PATH}nm
+
+            if [ -z "${alt_libc}" ]; then
+              alt_libc=`find "${SDK_PATH}" -name arch-arm -print | \
+                awk '{n = split($0,a,"/"); \
                 split(a[n-1],b,"-"); \
                 print $0 " " b[2]}' | \
                 sort -g -k 2 | \
                 awk '{ print $1 }' | tail -1`
-          fi
+            fi
 
-          if [ -d "${alt_libc}" ]; then
-            add_cflags "--sysroot=${alt_libc}"
-            add_ldflags "--sysroot=${alt_libc}"
-          fi
+            if [ -d "${alt_libc}" ]; then
+              add_cflags "--sysroot=${alt_libc}"
+              add_ldflags "--sysroot=${alt_libc}"
+            fi
 
-          # linker flag that routes around a CPU bug in some
-          # Cortex-A8 implementations (NDK Dev Guide)
-          add_ldflags "-Wl,--fix-cortex-a8"
+            # linker flag that routes around a CPU bug in some
+            # Cortex-A8 implementations (NDK Dev Guide)
+            add_ldflags "-Wl,--fix-cortex-a8"
 
-          enable_feature pic
-          soft_enable realtime_only
-          if [ ${tgt_isa} = "armv7" ]; then
-            soft_enable runtime_cpu_detect
-          fi
-          if enabled runtime_cpu_detect; then
-            add_cflags "-I${SDK_PATH}/sources/android/cpufeatures"
+            enable_feature pic
+            soft_enable realtime_only
+            if [ ${tgt_isa} = "armv7" ]; then
+              soft_enable runtime_cpu_detect
+            fi
+            if enabled runtime_cpu_detect; then
+              add_cflags "-I${SDK_PATH}/sources/android/cpufeatures"
+            fi
+          else
+            echo "Assuming standalone build with NDK toolchain."
+            echo "See build/make/Android.mk for details."
+            check_add_ldflags -static
+            soft_enable unit_tests
           fi
           ;;
 
@@ -1392,6 +1395,7 @@ EOF
       *-win*-vs*)
         ;;
       *-android-gcc)
+        # bionic includes basic pthread functionality, obviating -lpthread.
         ;;
       *)
         check_header pthread.h && add_extralibs -lpthread