Adds options to configure in a similar fashion and with similar

constraints to the options added in `swift` to add Android Support.
This will allow initially those features to be just passed from
`utils/build-script` without any change until a full strategy for
cross-compilation in all the involved projects is defined.

This is an example call to build for Android with Swift support:
```
env \
CC="${swift_android_path}/build/Ninja-ReleaseAssert/llvm-linux-x86_64/bi
n/clang" \
CXX="${swift_android_path}/build/Ninja-ReleaseAssert/llvm-linux-x86_64/b
in/clang++" \
SWIFTC="${swift_android_path}/build/Ninja-ReleaseAssert/swift-linux-x86_
64/bin/swiftc" \
${swift_android_path}/swift-corelibs-libdispatch/configure \
--with-swift-toolchain=“${swift_android_path}/build/Ninja-ReleaseAssert/
swift-linux-x86_64/" \
--with-build-variant=release \
--enable-android \
--host=arm-linux-androideabi \
--with-android-ndk=${ndk_path} \
--with-android-api-level=21 \
--disable-build-tests
```

Author: gonzalolarralde

Makefile.am

@@ -12,6 +12,10 @@ if BUILD_OWN_KQUEUES
   MAYBE_KQUEUES = libkqueue
 endif
 
+if BUILD_TESTS
+  MAYBE_TESTS = tests
+endif
+
 SUBDIRS=						\
 	dispatch					\
 	$(MAYBE_PTHREAD_WORKQUEUES)	\
@@ -20,7 +24,7 @@ SUBDIRS=						\
 	os							\
 	private						\
 	src							\
-	tests
+	$(MAYBE_TESTS)
 
 EXTRA_DIST=					\
 	README.md				\

configure.ac

@@ -11,6 +11,10 @@ AC_CONFIG_MACRO_DIR([m4])
 ac_clean_files=a.out.dSYM
 AM_MAINTAINER_MODE
 
+AC_CANONICAL_BUILD
+AC_CANONICAL_HOST
+AC_CANONICAL_TARGET
+
 #
 # Command line argument to specify build variant (default to release).
 # Impacts default value of CFLAGS et al. so must come before AC_PROG_CC
@@ -56,6 +60,53 @@ AC_PROG_CXX([clang++ g++ c++])
 AC_PROG_OBJC([clang gcc cc])
 AC_PROG_OBJCXX([clang++ g++ c++])
 
+#
+# Android cross-compilation support
+#
+AC_ARG_WITH([android-ndk],
+  [AS_HELP_STRING([--with-android-ndk],
+    [Android NDK location])], [
+  android_ndk=${withval}
+])
+AC_ARG_WITH([android-ndk-gcc-version],
+  [AS_HELP_STRING([--with-android-ndk-gcc-version],
+    [Android NDK GCC version [defaults=4.9]])],
+  [android_ndk_gcc_version=${withval}], [android_ndk_gcc_version=4.9])
+AC_ARG_WITH([android-api-level],
+  [AS_HELP_STRING([--with-android-api-level],
+    [Android API level to link with])], [
+  android_api_level=${withval}
+])
+AC_ARG_ENABLE([android],
+  [AS_HELP_STRING([--enable-android],
+    [Compile for Android])], [
+  android=true
+
+  # Override values until there's real support for multiple Android platforms
+  host=armv7-none-linux-androideabi
+  host_alias=arm-linux-androideabi
+  host_cpu=armv7
+  host_os=linux-androideabi
+  host_vendor=unknown
+  arch=arm
+
+  sysroot=${android_ndk}/platforms/android-${android_api_level}/arch-${arch}
+  toolchain=${android_ndk}/toolchains/${host_alias}-${android_ndk_gcc_version}/prebuilt/linux-${build_cpu}
+
+  CFLAGS="$CFLAGS -target ${host_alias} --sysroot=${sysroot} -B${toolchain}/${host_alias}/bin"
+  CXXFLAGS="$CXXFLAGS -target ${host_alias} --sysroot=${sysroot} -B${toolchain}/${host_alias}/bin"
+  SWIFTC_FLAGS="-target ${host} -sdk ${sysroot} -L${toolchain}/lib/gcc/${host_alias}/${android_ndk_gcc_version}.x"
+  LIBS="$LIBS -L${toolchain}/lib/gcc/${host_alias}/${android_ndk_gcc_version}.x"
+  LDFLAGS="$LDFLAGS -Wc,'-target','${host_alias}','-B${toolchain}/${host_alias}/bin'"
+
+  # FIXME: empty CFLAGS and CXXFLAGS are assumed for this to work.
+  # FIXME: there should be a more elegant way to do this
+  ac_configure_args=`echo $ac_configure_args | sed -e "s/ 'CFLAGS='//" -e "s/ 'CXXFLAGS='//"`
+  # CFLAGS, CXXFLAGS and LIBS needs to be passed to libkqueue and libpwq
+  ac_configure_args="$ac_configure_args --enable-bionic-libc 'CFLAGS=$CFLAGS' 'CXXFLAGS=$CXXFLAGS' 'LIBS=$LIBS'"
+], [android=false])
+AM_CONDITIONAL(ANDROID, $android)
+
 #
 # On Mac OS X, some required header files come from other source packages;
 # allow specifying where those are.
@@ -134,8 +185,6 @@ AS_IF([test "x$enable_apple_tsd_optimizations" = "xyes"],
     [Define to use non-portable pthread TSD optimizations for Mac OS X)])]
 )
 
-AC_CANONICAL_TARGET
-
 #
 # Enable building Swift overlay support into libdispatch
 #
@@ -164,6 +213,7 @@ AC_ARG_WITH([swift-toolchain],
 )
 AM_CONDITIONAL(HAVE_SWIFT, $have_swift)
 AC_SUBST([SWIFTC])
+AC_SUBST([SWIFTC_FLAGS])
 AC_SUBST([SWIFT_LIBDIR])
 
 #
@@ -461,6 +511,13 @@ AC_COMPILE_IFELSE(
   [AC_DEFINE(HAVE_NORETURN_BUILTIN_TRAP, 1, [Define if __builtin_trap marked noreturn])]
 )
 
+#
+# Add option to avoid building tests
+#
+AC_ARG_ENABLE([build-tests],
+  [AS_HELP_STRING([--disable-build-tests], [Disable tests compilation])])
+AM_CONDITIONAL(BUILD_TESTS, [test "x$enable_build_tests" != "xno"])
+
 #
 # Generate Makefiles.
 #

src/Makefile.am

@@ -41,6 +41,7 @@ libdispatch_la_SOURCES=		\
 	trace.h					\
 	voucher_internal.h		\
 	firehose/firehose_internal.h \
+	shims/android_stubs.h	\
 	shims/atomic.h			\
 	shims/atomic_sfb.h		\
 	shims/getprogname.h		\
@@ -64,6 +65,7 @@ DISPATCH_CFLAGS=-Wall $(VISIBILITY_FLAGS) $(OMIT_LEAF_FP_FLAGS) \
 if DISPATCH_ENABLE_ASSERTS
 DISPATCH_CFLAGS+=-DDISPATCH_DEBUG=1
 endif
+
 AM_CFLAGS= $(KQUEUE_CFLAGS) $(PTHREAD_WORKQUEUE_CFLAGS) $(DISPATCH_CFLAGS) $(CBLOCKS_FLAGS)
 AM_OBJCFLAGS=$(DISPATCH_CFLAGS) $(CBLOCKS_FLAGS)
 AM_CXXFLAGS=$(KQUEUE_CFLAGS) $(PTHREAD_WORKQUEUE_CFLAGS) $(DISPATCH_CFLAGS) $(CXXBLOCKS_FLAGS)
@@ -164,7 +166,7 @@ SWIFT_GEN_FILES=	\
 	$(SWIFT_OBJ_FILES:%=%.~partial.swiftdoc) \
 	$(SWIFT_OBJ_FILES:%=%.~partial.swiftdeps)
 
-SWIFTC_FLAGS = -Xcc -fmodule-map-file=$(abs_top_srcdir)/dispatch/module.modulemap -I$(abs_top_srcdir) -Xcc -fblocks
+SWIFTC_FLAGS+= -Xcc -fmodule-map-file=$(abs_top_srcdir)/dispatch/module.modulemap -I$(abs_top_srcdir) -Xcc -fblocks
 if DISPATCH_ENABLE_OPTIMIZATION
 SWIFTC_FLAGS+=-O
 endif

src/internal.h

@@ -155,6 +155,7 @@
 #endif
 
 /* private.h must be included last to avoid picking up installed headers. */
+#include <pthread.h>
 #include "os/object_private.h"
 #include "queue_private.h"
 #include "source_private.h"
@@ -245,7 +246,11 @@ DISPATCH_EXPORT DISPATCH_NOTHROW void dispatch_atfork_child(void);
 #include <sys/event.h>
 #include <sys/mount.h>
 #include <sys/queue.h>
+#ifdef __ANDROID__
+#include <linux/sysctl.h>
+#else
 #include <sys/sysctl.h>
+#endif /* __ANDROID__ */
 #include <sys/socket.h>
 #include <sys/time.h>
 #include <sys/mman.h>

src/queue.c

@@ -976,6 +976,7 @@ _dispatch_get_mach_host_port(void)
 #include <unistd.h>
 #include <sys/syscall.h>
 
+#ifndef __ANDROID__
 #ifdef SYS_gettid
 DISPATCH_ALWAYS_INLINE
 static inline pid_t
@@ -985,7 +986,8 @@ gettid(void)
 }
 #else
 #error "SYS_gettid unavailable on this system"
-#endif
+#endif /* SYS_gettid */
+#endif /* ! __ANDROID__ */
 
 #define _tsd_call_cleanup(k, f)  do { \
 		if ((f) && tsd->k) ((void(*)(void*))(f))(tsd->k); \

src/shims.h

@@ -97,6 +97,10 @@ typedef unsigned long pthread_priority_t;
 #include "shims/linux_stubs.h"
 #endif
 
+#ifdef __ANDROID__
+#include "shims/android_stubs.h"
+#endif
+
 typedef uint32_t dispatch_priority_t;
 #define DISPATCH_SATURATED_OVERRIDE ((dispatch_priority_t)UINT32_MAX)
 

src/shims/android_stubs.h

@@ -0,0 +1,34 @@
+/*
+ * This source file is part of the Swift.org open source project
+ *
+ * Copyright (c) 2015 Apple Inc. and the Swift project authors
+ *
+ * Licensed under Apache License v2.0 with Runtime Library Exception
+ *
+ * See http://swift.org/LICENSE.txt for license information
+ * See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+ *
+ */
+
+// forward declarations for functions we are stubbing out
+// in the intial android port.
+
+#ifndef __DISPATCH__ANDROID__STUBS__INTERNAL
+#define __DISPATCH__ANDROID__STUBS__INTERNAL
+
+/*
+ * Missing sys/queue.h macro stubs
+ */
+
+#ifndef TAILQ_FOREACH_SAFE
+#	define TAILQ_FOREACH_SAFE(var, head, field, tvar)                      \
+    	    for ((var) = TAILQ_FIRST((head));                              \
+        	    (var) && ((tvar) = TAILQ_NEXT((var), field), 1);           \
+            	(var) = (tvar))
+#endif /* TAILQ_FOREACH_SAFE */
+
+#ifndef TRASHIT
+#	define TRASHIT(x)      do {(x) = (void *)-1;} while (0)
+#endif /* TRASHIT */
+
+#endif /* __DISPATCH__ANDROID__STUBS__INTERNAL */

src/shims/getprogname.h

@@ -23,11 +23,18 @@
 #define __DISPATCH_SHIMS_GETPROGNAME__
 
 #if !HAVE_GETPROGNAME
+
+#ifdef __ANDROID__
+extern const char *__progname;
+#endif /* __ANDROID */)
+
 static inline char *
 getprogname(void)
 {
 # if HAVE_DECL_PROGRAM_INVOCATION_SHORT_NAME
 	return program_invocation_short_name;
+# elif defined(__ANDROID__)
+	return __progname;
 # else
 #   error getprogname(3) is not available on this platform
 # endif

src/shims/linux_stubs.c

@@ -17,7 +17,11 @@
  */
 
 #include <stdint.h>
+#ifdef __ANDROID__
+#include <sys/syscall.h>
+#else
 #include <syscall.h>
+#endif /* __ANDROID__ */
 
 #if __has_include(<config/config_ac.h>)
 #include <config/config_ac.h>

src/shims/linux_stubs.h

@@ -71,7 +71,9 @@ typedef void (*dispatch_mach_msg_destructor_t)(void*);
 #endif
 
 // SIZE_T_MAX should not be hardcoded like this here.
-#define SIZE_T_MAX (0x7fffffff)
+#ifndef SIZE_T_MAX
+#define SIZE_T_MAX (~(size_t)0)
+#endif
 
 // Define to 0 the NOTE_ values that are not present on Linux.
 // Revisit this...would it be better to ifdef out the uses instead??