Notes on Android SDK dev

A share about Android NDK - build c/c++ code into shared lib app uses

Android.mk - glue the c/c++ code to the Android NDK
- defines properties specific to individual modules, or libs
Application.mk - defines properties for all the modules that app uses
ndk-build -
toolchain
the dev tool is so important (eclipse is so terrible for this task)

Linking - concatenates blocks together, and decides on run-time locations for the concatenated blocks
- symbol resolution step - symbol table in .symtab associate each global symbol (functions and global variables) reference with a unique symbol definition
- relocation - associate a memory location with each symbol definition, and then make them point to the memory location meger all sections of the same type into a new aggregate section relocate symbol references so that they point to the correct run-time addresses
linking with static libraries
- related functions can be compiled into separate object modules and then packaged in a single static library file; At link time, the linker will copy only the object modules(symbol resolution) that are referenced by the program.
advantages need to maintain and update the static libraries periodically
At run time, the code of the functions like I/O functions is duplicated in the text segment of each running process
dynamic linking with shared libraries
- a single copy of the .text section of a shared libray in memory can be shared by different running
the basic idea is to link the relocation and symbol table info when the executable file is created, and then complete the linking process (code and data ) dynamically when the program is loaded