2017-07-27 10:46 GMT+02:00 Pablo Neira Ayuso <pablo@netfilter.org>:
> Cc'ing Pablo Bermudo.
>
> On Wed, Jul 26, 2017 at 06:16:30PM +0200, Phil Sutter wrote:
>> Remove the functions mnl_nft_rule_add() and *_delete() since they are
>> not used throughout the code. Commit a72315d2bad47 ("src: add rule
>> batching support") changed their only caller to use the batch variant
>> introduced at the same time.
>
> I think there are more useless functions. Pablo Bermudo mentioned this
> to me a while ago. At least I remember some of them in netlink.c?
>
> If not much asking, it would be good if we can kill them all in one go.

I am using a combination of compiler and linker options in order to obtain
a list of unused functions:

  $ make -j5 CFLAGS="-ffunction-sections -fdata-sections
-Wl,--gc-sections,--print-gc-sections"

You can find more information about --gc-sections and its pitfalls here [1].
The listing is printed on stderr by --print-gc-sections and it looks like this:

/usr/bin/ld: Removing unused section '.text.xt_stmt_xlate' in file 'statement.o'
/usr/bin/ld: Removing unused section '.text.xt_stmt_release' in file
'statement.o'
/usr/bin/ld: Removing unused section '.text.xt_stmt_print' in file 'statement.o'
...

There is also a small utility called callcatcher [2], written by LibreOffice
developer Caolán McNamara. But it seems not to be recursive, so unused
functions invoked from other unused functions are not shown until the callers
are deleted.

The complete list contains some functions that I think are not worth removing,
because are part of a "consolidated API" (e.g. those related to the
implementation of the red–black tree). A bunch of unused functions are
from the auto-generated file scanner.c.

The current list is attached.

--

[1] http://elinux.org/images/2/2d/ELC2010-gc-sections_Denys_Vlasenko.pdf
[2] http://www.skynet.ie/~caolan/Packages/callcatcher.html