Cross compilation support (#709)

* build: add cross-compilation support to make

Set CROSS_COMPILE when running make to use the selected cross
compilation toolchain, such as arm-linux-gnueabihf, or
aarch64-linux-gnu.

Testing requires the presence of qemu - 'qemu-$(ARCH)' will be executed,
where ARCH is the first part of the toolchain triplet.

* build: add cross-compilation support to cmake

If C_COMPILER/CXX_COMPILER/CC/CXX are found to have cross-compilation
triplets in front of the compiler, then qemu will be used to execute the
tests.

* CI: add arm-linux-gnueabihf-gcc builder to Travis

The version of qemu available in Ubuntu trusty (as provided by Travis)
appears to have a bug in qemu-aarch64, which leads to the compatibility
tests failing on some inputs, erroneously rejecting the input as
corrupt.

Once Travis supports xenial, we could add an aarch64-gnu-linux-gcc
builder as well.

* CI: propagate cmake errors out of .travis.sh

Seems like even if cmake fails, the error isn't picked up by Travis.

8 files changed, 71 insertions, 11 deletions

diff --git a/.travis.yml b/.travis.yml
index fba9c55..f300519 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -76,6 +76,20 @@ matrix:
           - clang-3.5
 
     ###
+    ## testing arm via qemu on Linux
+    ###
+    - os: linux
+      env: BUILD_SYSTEM=cmake C_COMPILER=arm-linux-gnueabihf-gcc CXX_COMPILER=arm-linux-gnueabihf-g++
+      addons:
+        apt:
+          sources:
+          - ubuntu-toolchain-r-test
+          packages:
+          - qemu
+          - gcc-arm-linux-gnueabihf
+          - libc6-dev-armhf-cross
+
+    ###
     ## PGI Community Edition on Linux
     ###
     - os: linux
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6f1c5a2..fc45f80 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -218,15 +218,37 @@ endif()
 # to run the tests...
 if(NOT BROTLI_DISABLE_TESTS)
   if(WIN32 AND NOT CMAKE_HOST_WIN32)
-    find_program(BROTLI_WINE NAMES wine)
+    find_program(BROTLI_WRAPPER NAMES wine)
 
-    if(NOT BROTLI_WINE)
+    if(NOT BROTLI_WRAPPER)
       message(STATUS "wine not found, disabling tests")
       set(BROTLI_DISABLE_TESTS TRUE)
     endif()
   endif()
 endif()
 
+# If our compiler is a cross-compiler that we know about (arm/aarch64),
+# then we need to use qemu to execute the tests.
+if(NOT BROTLI_DISABLE_TESTS)
+  if ("${CMAKE_C_COMPILER}" MATCHES "^.*/arm-linux-gnueabihf-.*$")
+    message(STATUS "Detected arm-linux-gnueabihf cross-compilation")
+    set(BROTLI_WRAPPER "qemu-arm")
+    set(BROTLI_WRAPPER_LD_PREFIX "/usr/arm-linux-gnueabihf")
+  endif()
+
+  if ("${CMAKE_C_COMPILER}" MATCHES "^.*/arm-linux-gnueabi-.*$")
+    message(STATUS "Detected arm-linux-gnueabi cross-compilation")
+    set(BROTLI_WRAPPER "qemu-arm")
+    set(BROTLI_WRAPPER_LD_PREFIX "/usr/arm-linux-gnueabi")
+  endif()
+
+  if ("${CMAKE_C_COMPILER}" MATCHES "^.*/aarch64-linux-gnu-.*$")
+    message(STATUS "Detected aarch64-linux-gnu cross-compilation")
+    set(BROTLI_WRAPPER "qemu-aarch64")
+    set(BROTLI_WRAPPER_LD_PREFIX "/usr/aarch64-linux-gnu")
+  endif()
+endif()
+
 if(NOT BROTLI_DISABLE_TESTS)
   include(CTest)
   enable_testing()
@@ -249,7 +271,8 @@ if(NOT BROTLI_DISABLE_TESTS)
     foreach(quality 1 6 9 11)
       add_test(NAME "${BROTLI_TEST_PREFIX}roundtrip/${INPUT}/${quality}"
         COMMAND "${CMAKE_COMMAND}"
-          -DBROTLI_WRAPPER=${BROTLI_WINE}
+          -DBROTLI_WRAPPER=${BROTLI_WRAPPER}
+          -DBROTLI_WRAPPER_LD_PREFIX=${BROTLI_WRAPPER_LD_PREFIX}
           -DBROTLI_CLI=$<TARGET_FILE:brotli>
           -DQUALITY=${quality}
           -DINPUT=${INPUT_FILE}
@@ -266,7 +289,8 @@ if(NOT BROTLI_DISABLE_TESTS)
   foreach(INPUT ${COMPATIBILITY_INPUTS})
     add_test(NAME "${BROTLI_TEST_PREFIX}compatibility/${INPUT}"
       COMMAND "${CMAKE_COMMAND}"
-        -DBROTLI_WRAPPER=${BROTLI_WINE}
+        -DBROTLI_WRAPPER=${BROTLI_WRAPPER}
+        -DBROTLI_WRAPPER_LD_PREFIX=${BROTLI_WRAPPER_LD_PREFIX}
         -DBROTLI_CLI=$<TARGET_FILE:brotli>
         -DINPUT=${CMAKE_CURRENT_SOURCE_DIR}/${INPUT}
         -P ${CMAKE_CURRENT_SOURCE_DIR}/tests/run-compatibility-test.cmake)
diff --git a/Makefile b/Makefile
index c48d798..58e563a 100644
--- a/Makefile
+++ b/Makefile
@@ -15,6 +15,18 @@ ifeq ($(os), Darwin)
   CPPFLAGS += -DOS_MACOSX
 endif
 
+ifneq ($(strip $(CROSS_COMPILE)), )
+	CC=$(CROSS_COMPILE)-gcc
+	ARCH=$(firstword $(subst -, ,$(CROSS_COMPILE)))
+	BROTLI_WRAPPER="qemu-$(ARCH) -L /usr/$(CROSS_COMPILE)"
+endif
+
+# The arm-linux-gnueabi compiler defaults to Armv5. Since we only support Armv7
+# and beyond, we need to select Armv7 explicitly with march.
+ifeq ($(ARCH), arm)
+	CFLAGS += -march=armv7-a
+endif
+
 all: test
 	@:
 
@@ -31,8 +43,8 @@ lib: $(LIBOBJECTS)
 	ar -crs $(LIB_A) $(LIBOBJECTS)
 
 test: $(EXECUTABLE)
-	tests/compatibility_test.sh
-	tests/roundtrip_test.sh
+	tests/compatibility_test.sh $(BROTLI_WRAPPER)
+	tests/roundtrip_test.sh $(BROTLI_WRAPPER)
 
 clean:
 	rm -rf $(BINDIR) $(LIB_A)
diff --git a/scripts/.travis.sh b/scripts/.travis.sh
index 6387e22..367cdfa 100755
--- a/scripts/.travis.sh
+++ b/scripts/.travis.sh
@@ -40,9 +40,9 @@ case "$1" in
 		if [ "${CROSS_COMPILE}" = "yes" ]; then
 		    CMAKE_FLAGS="-DCMAKE_FIND_ROOT_PATH_MODE_PROGRAM=NEVER -DCMAKE_FIND_ROOT_PATH_MODE_LIBRARY=ONLY -DCMAKE_FIND_ROOT_PATH_MODE_INCLUDE=ONLY -DCMAKE_SYSTEM_NAME=Windows -DCMAKE_RC_COMPILER=${RC_COMPILER}"
 		fi
-		cmake ${CMAKE_FLAGS} -DCMAKE_C_COMPILER="$CC" -DCMAKE_CXX_COMPILER="$CXX" -DENABLE_SANITIZER="${SANITIZER}" -DCMAKE_C_FLAGS="${CFLAGS}" ..
-		make VERBOSE=1
-		ctest -V
+		cmake ${CMAKE_FLAGS} -DCMAKE_C_COMPILER="$CC" -DCMAKE_CXX_COMPILER="$CXX" -DENABLE_SANITIZER="${SANITIZER}" -DCMAKE_C_FLAGS="${CFLAGS}" .. || exit 1
+		make VERBOSE=1 || exit 1
+		ctest -V || exit 1
 		;;
 	    "python")
 		python setup.py test
diff --git a/tests/compatibility_test.sh b/tests/compatibility_test.sh
index 4026fd9..c5af8bf 100755
--- a/tests/compatibility_test.sh
+++ b/tests/compatibility_test.sh
@@ -2,10 +2,13 @@
 #
 # Test that the brotli command-line tool can decompress old brotli-compressed
 # files.
+#
+# The first argument may be a wrapper for brotli, such as 'qemu-arm'.
 
 set -o errexit
 
-BROTLI=bin/brotli
+BROTLI_WRAPPER=$1
+BROTLI="${BROTLI_WRAPPER} bin/brotli"
 TMP_DIR=bin/tmp
 
 for file in tests/testdata/*.compressed*; do
diff --git a/tests/roundtrip_test.sh b/tests/roundtrip_test.sh
index 6c92418..90027af 100755
--- a/tests/roundtrip_test.sh
+++ b/tests/roundtrip_test.sh
@@ -1,10 +1,13 @@
 #!/usr/bin/env bash
 #
 # Roundtrip test for the brotli command-line tool.
+#
+# The first argument may be a wrapper for brotli, such as 'qemu-arm'.
 
 set -o errexit
 
-BROTLI=bin/brotli
+BROTLI_WRAPPER=$1
+BROTLI="${BROTLI_WRAPPER} bin/brotli"
 TMP_DIR=bin/tmp
 INPUTS="""
 tests/testdata/alice29.txt
diff --git a/tests/run-compatibility-test.cmake b/tests/run-compatibility-test.cmake
index fd49db8..f594d98 100644
--- a/tests/run-compatibility-test.cmake
+++ b/tests/run-compatibility-test.cmake
@@ -2,6 +2,8 @@ string(REGEX REPLACE "([a-zA-Z0-9\\.]+)\\.compressed(\\.[0-9]+)?$" "\\1" REFEREN
 string(REGEX REPLACE "\\.compressed" "" OUTPUT_FILE "${INPUT}")
 get_filename_component(OUTPUT_NAME "${OUTPUT_FILE}" NAME)
 
+set(ENV{QEMU_LD_PREFIX} "${BROTLI_WRAPPER_LD_PREFIX}")
+
 execute_process(
   WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
   COMMAND ${BROTLI_WRAPPER} ${BROTLI_CLI} --force --decompress ${INPUT} --output=${CMAKE_CURRENT_BINARY_DIR}/${OUTPUT_NAME}.unbr
diff --git a/tests/run-roundtrip-test.cmake b/tests/run-roundtrip-test.cmake
index 08d4e01..39303d3 100644
--- a/tests/run-roundtrip-test.cmake
+++ b/tests/run-roundtrip-test.cmake
@@ -1,3 +1,5 @@
+set(ENV{QEMU_LD_PREFIX} "${BROTLI_WRAPPER_LD_PREFIX}")
+
 execute_process(
   WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
   COMMAND ${BROTLI_WRAPPER} ${BROTLI_CLI} --force --quality=${QUALITY} ${INPUT} --output=${OUTPUT}.br