How to use precompiled headers in Android NDK project?

Had the same problem, so there is a solution. First of all, as it seems to be you are not able to do it with changing the android.mk files, you should change file in the ndk built system, but this is not very dangerous %). This solution tested on r8b NDK. So:

• Add the following code to the /build/core/build-binary.mk script, before # Build the sources to object files:

    #precompiled helper:    ifeq ($(TARGET_ARCH_ABI),x86)        $(call set-src-files-target-cflags,$(LOCAL_PCH),)    else        $(call set-src-files-target-cflags,$(LOCAL_PCH),-mthumb)    endif    # Build PCH    #    get-pch-name = $(strip \        $(subst ../,__/,\            $(eval __pch := $1)\            $(eval __pch := $(__pch:%.h=%.precompiled.h))\            $(__pch)\        ))    ifneq (,$(findstring DPCH,$(call module-get-c++-flags,$(LOCAL_MODULE))))        # Build PCH into obj directory        LOCAL_BUILT_PCH := $(call get-pch-name,$(LOCAL_PCH))        $(call ndk_log, ___________________________Building pch '$(LOCAL_BUILT_PCH)'___________________________)        # Build PCH        $(call compile-cpp-source,$(LOCAL_PCH),$(LOCAL_BUILT_PCH).gch)        # All obj files are dependent on the PCH        $(foreach src,$(filter $(all_cpp_patterns),$(LOCAL_SRC_FILES)),\            $($(LOCAL_OBJS_DIR)/$(call get-object-name,$(src)) : $(LOCAL_OBJS_DIR)/$(LOCAL_BUILT_PCH).gch)\        )        # Files from now on build with PCH        LOCAL_CPPFLAGS += -Winvalid-pch -include $(LOCAL_BUILT_PCH)        # Insert PCH dir at beginning of include search path        LOCAL_C_INCLUDES := \            $(LOCAL_OBJS_DIR) \            $(LOCAL_C_INCLUDES)    else       $(call ndk_log, ___________________________NO PCH for this module___________________________)    endif    

• Insert the following lines to your android.mk of your module:

    PCH_FILE := symroot/src/Prefix.h    LOCAL_PCH := $(PCH_FILE)    LOCAL_CPPFLAGS += -DPCH

So we mark our module as having the precompiled header with -DPCH compilator flag (tricky, but work when there are a lot of modules in the application).

The most of solution is taken from here: http://code.google.com/p/android/issues/detail?id=25412

WARNING: after I have done this with my project, it did not give me compilation time improvement at all, and i found that this happens with gcc precompiled headers on some projects. Can't explain myself this yet.

If you want just include some file into every cpp file, just add the following lines to android.mk:

    PCH_FILE := $(LOCAL_PATH)/symroot/src/Prefix.h    LOCAL_CPPFLAGS += -include $(PCH_FILE)