OSX C/C++ Header Differences with Linux

• Header <mntent.h> does not exist
• Header <linux/rtc.h> does not exist
• Header <sys/sysinfo.h> does not exist
• In <string.h>, function strndup() does not exist
• In <unistd.h>, function ftruncate64() does not exist
• In <netinet/in.h>, struct ip_mreqn does not exist
• Struct statfs requires <sys/param.h> and <sys/mount.h>
• Variable environ doest not exists, but you can "access" it using function _NSGetEnviron() defined in <crt_externs.h>
• To retrieve full path of current executable, use function _NSGetExecutablePath() defined in <mach-o/dyld.h>

Android NDK Differences with Linux

• C++ STL is not included Update: stlport is included since revision 5
• In <mntent.h>, function setmntent() does not exist
• In <dirent.h>, functions seekdir(), telldir() does not exist
• Macro INET_ADDRSTRLEN is not defined in <netinet/in.h> Update: added since revision 5b
• Macro PTHREAD_EXPLICIT_SCHED is not defined in <pthread.h>
• Marcos WEXITSTATUS, WTERMSIG, WIFSIGNALED, etc are only defined in <sys/wait.h>  (One can also find them in <stdlib.h>  for Linux)
• Although function ftruncate64() is included in header <unistd.h>, it is not included in the prebuilt libraries. Hence it causes linking error while this function is used
• Although you can include <sys/sysinfo.h>, struct sysinfo does not exist (it is disabled in the header file). If you have to use it, try this way.

Android NDK Development

Some remarks I would like to make while developing on Android NDK:

• Package, class and function names in Java are specified by function name in C/C++
• For all JNI wrapper functions, remember to add JNIEnv *env and jobject object to the front of the parameter list. They represent the environment pointer and the Java class object which calls this function.
• Parameters are passed into wrapper functions by value. To the best of my knowledge, there is no way to pass in parameters by reference.
• If the wrapper source is in cpp, remember to include all function prototypes in
  
• Include all source files in subdirectory src: LOCAL_SRC_FILES := $(addprefix src/,$(notdir $(wildcard $(LOCAL_PATH)/src/*.cpp $(LOCAL_PATH)/src/*.c)))
• Make use of include $(call all-subdir-makefiles) to make a recursive building hierarchy
• While using variable LOCAL_STATIC_LIBRARIES, try putting the highest level libraries in the front to prevent linking error
• In order tot check the output of stdout and stderr, you have to set by using adb (included in Android SDK), and then you can view them using ./adb logcat
  ./adb shell stop
  ./adb shell setprop log.redirect-stdio true
  ./adb shell start
  Update: Stopping and starting the shell may cause the whole emulator hangs now. To redirect stdout/stderr, add "log.redirect-stdio=true" to /data/local.prop on the device (create one if the file does not exist) and restart the device
• STL library is not included in NDK. If you need to use STL library in your NDK code, you have to use stlport
• DO NOT create thread inside NDK
• Directory /tmp DOES NOT exist in Android. I have tried to search for it for hours without any luck. According to what I found, applications should manage their own files (temp or non-temp) within the local filesystem sandbox on their own
• There is a script to let you build a NDK toolchain since NDK revision 5
• Linking with "-lpthread" is not required, including that will cause error