Allow building on Darwin/arm64

Changes:
1. `-soname` should be `-install_name` on Darwin
2. Version suffix should placed before extension suffix (libucontext.so.1 -> libucontext.1.dylib)
3. Check for architecture specific include directory, and include it while building
4. `EXPORT_UNPREFIXED` macro shouldn't be set since Darwin don't support aliases
5. Choose correct subdir for arm64
6. Use `-dynamiclib` instead of `-shared` on Darwin for adding version info (`-current_version` and `-compatibility_version`)

Makefile

@@ -13,13 +13,21 @@ endif
 ifeq ($(ARCH),$(filter $(ARCH),armv7l))
 	override ARCH = arm
 endif
+ifeq ($(ARCH),$(filter $(ARCH),arm64))
+	override ARCH = aarch64
+endif
 
 LIBDIR := /lib
 INCLUDEDIR := /usr/include
 PKGCONFIGDIR := /usr/lib/pkgconfig
 CFLAGS := -ggdb3 -O2 -Wall
 CPPFLAGS := -Iinclude -Iarch/${ARCH} -Iarch/common
-EXPORT_UNPREFIXED := yes
+ifneq ($(shell uname),Darwin)
+	EXPORT_UNPREFIXED := yes
+else
+	# Darwin does not support aliases
+	EXPORT_UNPREFIXED := no
+endif
 FREESTANDING := no
 
 ifeq ($(FREESTANDING),yes)
@@ -34,13 +42,30 @@ endif
 LIBUCONTEXT_C_SRC = $(wildcard arch/${ARCH}/*.c)
 LIBUCONTEXT_S_SRC = $(wildcard arch/${ARCH}/*.S)
 
+ifeq ($(shell test -d arch/${ARCH}/include; echo $?),0)
+	CPPFLAGS += -Iarch/${ARCH}/include
+endif
+
 LIBUCONTEXT_VERSION := $(shell head -n 1 VERSION)
 LIBUCONTEXT_OBJ = ${LIBUCONTEXT_C_SRC:.c=.o} ${LIBUCONTEXT_S_SRC:.S=.o}
 LIBUCONTEXT_SOVERSION = 1
-LIBUCONTEXT_NAME = libucontext.so
+ifeq ($(shell uname),Darwin)
+	LIBUCONTEXT_NAME = libucontext.dylib
+	LIBUCONTEXT_SONAME = libucontext.${LIBUCONTEXT_SOVERSION}.dylib
+	LIBUCONTEXT_POSIX_NAME = libucontext_posix.dylib
+	LIBUCONTEXT_POSIX_SONAME = libucontext_posix.${LIBUCONTEXT_SOVERSION}.dylib
+	LIBUCONTEXT_LINKER_FLAGS = -Wl,-dynamiclib,-install_name,${LIBUCONTEXT_SONAME},-current_version,${LIBUCONTEXT_SOVERSION},-compatibility_version,${LIBUCONTEXT_SOVERSION}
+	LIBUCONTEXT_POSIX_LINKER_FLAGS = -Wl,-dynamiclib,-install_name,${LIBUCONTEXT_POSIX_SONAME},-current_version,${LIBUCONTEXT_SOVERSION},-compatibility_version,${LIBUCONTEXT_SOVERSION}
+else
+	LIBUCONTEXT_NAME = libucontext.so
+	LIBUCONTEXT_SONAME = libucontext.so.${LIBUCONTEXT_SOVERSION}
+	LIBUCONTEXT_POSIX_NAME = libucontext_posix.so
+	LIBUCONTEXT_POSIX_SONAME = libucontext_posix.so.${LIBUCONTEXT_SOVERSION}
+	LIBUCONTEXT_LINKER_FLAGS = -Wl,-shared,-soname,${LIBUCONTEXT_SONAME}
+	LIBUCONTEXT_POSIX_LINKER_FLAGS = -Wl,-shared,-soname,${LIBUCONTEXT_POSIX_SONAME}
+endif
 LIBUCONTEXT_STATIC_NAME = libucontext.a
 LIBUCONTEXT_PC = libucontext.pc
-LIBUCONTEXT_SONAME = libucontext.so.${LIBUCONTEXT_SOVERSION}
 LIBUCONTEXT_PATH = ${LIBDIR}/${LIBUCONTEXT_SONAME}
 LIBUCONTEXT_STATIC_PATH = ${LIBDIR}/${LIBUCONTEXT_STATIC_NAME}
 LIBUCONTEXT_HEADERS = \
@@ -48,11 +73,9 @@ LIBUCONTEXT_HEADERS = \
 	include/libucontext/bits.h
 LIBUCONTEXT_EXAMPLES = \
 	examples/cooperative_threading
-LIBUCONTEXT_POSIX_NAME = libucontext_posix.so
 LIBUCONTEXT_POSIX_STATIC_NAME = libucontext_posix.a
 LIBUCONTEXT_POSIX_C_SRC = libucontext_posix.c
 LIBUCONTEXT_POSIX_OBJ = ${LIBUCONTEXT_POSIX_C_SRC:.c=.o}
-LIBUCONTEXT_POSIX_SONAME = libucontext_posix.so.${LIBUCONTEXT_SOVERSION}
 LIBUCONTEXT_POSIX_PATH = ${LIBDIR}/${LIBUCONTEXT_POSIX_SONAME}
 LIBUCONTEXT_POSIX_STATIC_PATH = ${LIBDIR}/${LIBUCONTEXT_POSIX_STATIC_NAME}
 
@@ -64,8 +87,7 @@ endif
 all: ${LIBUCONTEXT_SONAME} ${LIBUCONTEXT_STATIC_NAME} ${LIBUCONTEXT_POSIX_NAME} ${LIBUCONTEXT_POSIX_STATIC_NAME} ${LIBUCONTEXT_PC}
 
 ${LIBUCONTEXT_POSIX_NAME}: ${LIBUCONTEXT_NAME} ${LIBUCONTEXT_POSIX_OBJ}
-	$(CC) -fPIC -o ${LIBUCONTEXT_POSIX_NAME} -Wl,-soname,${LIBUCONTEXT_POSIX_SONAME} \
+	$(CC) -fPIC -o ${LIBUCONTEXT_POSIX_NAME} ${LIBUCONTEXT_POSIX_LINKER_FLAGS} ${LIBUCONTEXT_POSIX_OBJ} ${LDFLAGS}
-		-shared ${LIBUCONTEXT_POSIX_OBJ} ${LDFLAGS}
 
 ${LIBUCONTEXT_POSIX_STATIC_NAME}: ${LIBUCONTEXT_STATIC_NAME} ${LIBUCONTEXT_POSIX_OBJ}
 	$(AR) rcs ${LIBUCONTEXT_POSIX_STATIC_NAME} ${LIBUCONTEXT_POSIX_OBJ}
@@ -77,8 +99,7 @@ ${LIBUCONTEXT_STATIC_NAME}: ${LIBUCONTEXT_HEADERS} ${LIBUCONTEXT_OBJ}
 	$(AR) rcs ${LIBUCONTEXT_STATIC_NAME} ${LIBUCONTEXT_OBJ}
 
 ${LIBUCONTEXT_NAME}: ${LIBUCONTEXT_HEADERS} ${LIBUCONTEXT_OBJ}
-	$(CC) -fPIC -o ${LIBUCONTEXT_NAME} -Wl,-soname,${LIBUCONTEXT_SONAME} \
+	$(CC) -fPIC -o ${LIBUCONTEXT_NAME} ${LIBUCONTEXT_LINKER_FLAGS} ${LIBUCONTEXT_OBJ} ${LDFLAGS}
-		-shared ${LIBUCONTEXT_OBJ} ${LDFLAGS}
 
 ${LIBUCONTEXT_SONAME}: ${LIBUCONTEXT_NAME}
 	ln -sf ${LIBUCONTEXT_NAME} ${LIBUCONTEXT_SONAME}