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Re: Symbols which were not used, still in binary
- From: Brian Dessent <brian at dessent dot net>
- To: gcc-help at gcc dot gnu dot org
- Date: Wed, 28 Jun 2006 14:20:19 -0700
- Subject: Re: Symbols which were not used, still in binary
- References: <44A2DF65.8010704@web.de> <44A2E3C9.90201@eagercon.com>
- Reply-to: gcc-help at gcc dot gnu dot org
Michael Eager wrote:
> Arguably, the linker should know
> that add is not referenced and could remove it, but linkers are not
> usually able to slice and dice object files.
You address this limitation by compiling with "-ffunction-sections
-fdata-sections -Wl,--gc-sections". However, it's still better to use
"static" on these kinds of local functions that are only used from the
same .o file. This has a number of benefits:
- it ensures that internal functions of a library are not exported for
use by other code when they are not part of the defined ABI/API
- it prevents them from taking up needless relocations, which can slow
linking
- when compiled -fpic (as in a shared library) it allows for direct
calls to the function instead of having to go through the PLT which is
slower
- it allows the compiler freedom to inline
Brian