Notes on Android SDK dev

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

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)

about the linking [TO UPDATE]

• 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