Question

We’re facing an interesting topic. Lets say we have a special-functions.c file, basically a library.
We need to optimize the code as getting rid of all unused/unreferenced functions during the build process on-the-fly.
I’m not searching for generally unused (dead) code: some parts will be “dead” in case of compiling to one of the architectures, but it’s going to be used in an other architecture build.

Does anybody knows of flags, tools, methods, tricks to do this?
The compiler is standard gcc with ansi 99 C code.

EDIT
I know, this is mainly the part of the linker, but using gcc, the process is not really split into two parts.

Answer 1

From http://embeddedfreak.wordpress.com/2009/02/10/removing-unused-functionsdead-codes-with-gccgnu-ld/ :

• Compile with -fdata-sections to keep the data in separate data
  sections and -ffunction-sections to keep functions in separate
  sections, so they (data and functions) can be discarded if unused.
• Link with --gc-sections to remove unused sections.

For example:

gcc -Os -fdata-sections -ffunction-sections test.c -o test -Wl,--gc-sections