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GCC has a useful option to place each function into its own section during compile time (-ffunction-sections). It's useful to optimize away unused functions during linking the binary (-gc-sections).

I have a static library and don't have a source of it. The library has hundreds of functions, but they are all placed inside a single .text section. The code size is critical for my application (in fact, it's an embedded ARM application) and the GNU linker cannot optimize the unused functions away because they are all in a single section.

How can I move the functions from a compiled object file to their own sections?

Ivan Mikhailov
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  • Libraries as such do not really have used code. It's the applications that make use of it. Is your application statically linked against that library? What's the format of statically linked library? .a archives have separate files for functions, so this should work as expected. – domen Jul 09 '15 at 09:37
  • Yes, my application is statically linked against the library. The archive contains only two object files and one of them has a lot of code. My application uses only couple of functions from the library. – Ivan Mikhailov Jul 09 '15 at 09:50
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    Actually, the library was created with IAR compiler. If I link my application using the IAR linker, the linker successfully drops the unused functions. But GNU linker needs the functions in separate sections to optimize them. The difference is huge (27 kB with IAR linker vs 91 kB with GNU). – Ivan Mikhailov Jul 09 '15 at 09:53
  • Does `strip` on the final binary help? On a very basic test, it removes unused function for me. – domen Jul 09 '15 at 10:02
  • No, `strip` doesn't help. – Ivan Mikhailov Jul 09 '15 at 10:15

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