Difference between LOCAL_EXPORT_C_INCLUDES and LOCAL_C_INCLUDES

android, android-ndk

Solution

If a module adds the paths to `LOCAL_EXPORT_C_INCLUDES`, these paths will be added to `LOCAL_C_INCLUDES` definition of another module which uses this one with `LOCAL_STATIC_LIBRARIES` or `LOCAL_SHARED_LIBRARIES`.

Consider we have 2 modules, e.g. foo and bar and following is tree structure.

.
|-- Android.mk
|-- bar
|   |-- bar.c
|   |-- bar.h
|-- foo
    |-- foo.c
    `-- foo.h

bar uses foo as a static library. Since bar.c will need to include the foo.h, foo module has to add include path to `LOCAL_EXPORT_C_INCLUDES`. If bar is not used by any module, then it can add include path to `LOCAL_C_INCLUDES`.

Android.mk will look like this:

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := foo
LOCAL_SRC_FILES := foo/foo.c
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/foo
include $(BUILD_STATIC_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := bar
LOCAL_SRC_FILES := bar/bar.c
LOCAL_C_INCLUDES := $(LOCAL_PATH)/bar
LOCAL_STATIC_LIBRARIES := foo
include $(BUILD_SHARED_LIBRARY)

Please have a look at an example provided in android-ndk sample directory : `android-ndk-r9d/samples/module-exports`

Problem

Original source