I have a library stack that is not going to change, and an firmware that is going to use only this stack. Firmware will change alot along the way. I don't want to every time release the whole image(including library stack) because of limited memory and resources issue(This is an embedded application not a desktop or server). I just want to release the application image and that automatically be able to use the library image. I am not sure how to do it. I know in Windows for example this is handled by dll's. But this is an embedded application and has no OS. Binary images loads to memory and processor is going to execute it. Any experience/suggestions?
Toolchain: IAR 8051
This depends quite a bit on your tool-chain. Here's a possible high-view approach.
Compile your library into an executable image, setting your linker to use a particular portion of your flash memory space. You'll probably need a fake/stub entry function for the linker to be happy.
Once that is done, find all of the addresses of the symbols used by the library and instruct your linker as to those symbol locations when building your normal program, and do not instruct the link process to use the intermediary library objects when linking. Also instruct the linker to place the code into the section of flash that is update-able.
What you will then have is an image for the library, and the ability to build new versions of the main program image using at library.
This could probably be scripted if your linker output format is an unstripped elf (prior to converting to a binary for burning on the flash), and if your linker can accept a plain text file for instructions (both are true if you are using the gnu toolchains). I'd recommend scripting it for your sanity unless the library has very few externally visible functions and variables in it.
I do have to agree with some of the commentors; unless transferring the library is very hard, you should just build a single simple image that includes the library and push the whole thing. You might say the library will never change now, but inevitably something will come up that requires a change to the library code, and if you change the library and cannot keep the symbols in exactly the same spot, all of your application images will not be able to work with the new library. This is a recipe for a nightmare when dealing with compatible software (firmware) updates.