Way to leave-out unused functions while linking to a library

Way to leave-out unused functions while linking to a library

[Shriramana Sharma]

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I asked this question on this list some time back, IIRC -- how to leave-out 
unused functions while linking to a library?

The normal behaviour is that if a library.c contains two functions fna() and 
fnb() and main.c calls only fna(), compiling library.c and main.c and linking 
to form an executable will result in the fnb() function getting included in 
the final executable, though it is never used in the entire course of the 
program.

So how to stop fnb() from getting linked in?

Over at the GNU GCC list, a good soul gave us the solution. Use -

-ffunction-sections -fdata-sections 

as compiler options and 

--gc-sections 

as a linker option. If you are calling the linker indirectly via the compiler 
gcc (i.e. if you are directly creating executables using gcc without a 
separate call to ld) then give it the options: 

-ffunction-sections -fdata-sections -Wl,--gc-sections 

[exactly as it is, with the comma] so that the compiler passes the appropriate 
option on to the linker. This method worked for me!

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