Re: [RFC 00/31] objtool, livepatch: Livepatch module generation

[Song Liu]

On Sat, Sep 7, 2024 at 1:14 PM Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
>
> On Sat, Sep 07, 2024 at 10:43:10AM -0700, Song Liu wrote:
> > clang gives the following:
> >
> > elf.c:102:1: error: unused function '__sym_remove' [-Werror,-Wunused-function]
> >   102 | INTERVAL_TREE_DEFINE(struct symbol, node, unsigned long, __subtree_last,
> >       | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   103 |                      __sym_start, __sym_last, static inline, __sym)
> >       |                      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > /data/users/songliubraving/kernel/linux-git/tools/include/linux/interval_tree_generic.h:65:15:
> > note: expanded from macro 'INTERVAL_TREE_DEFINE'
> >    65 | ITSTATIC void ITPREFIX ## _remove(ITSTRUCT *node,
> >                \
> >       |               ^~~~~~~~~~~~~~~~~~~
> > <scratch space>:155:1: note: expanded from here
> >   155 | __sym_remove
> >       | ^~~~~~~~~~~~
> > 1 error generated.
>
> Here's how __sym_remove() is created:
>
> #define INTERVAL_TREE_DEFINE(ITSTRUCT, ITRB, ITTYPE, ITSUBTREE,               \
>                              ITSTART, ITLAST, ITSTATIC, ITPREFIX)             \
> ...
>
> ITSTATIC void ITPREFIX ## _remove(ITSTRUCT *node,                             \
>                                   struct rb_root_cached *root)                \
>
> INTERVAL_TREE_DEFINE(struct symbol, node, unsigned long, __subtree_last,
>                      __sym_start, __sym_last, static inline, __sym)
>
> ITSTATIC is 'static inline' so it shouldn't be complaining about it
> being unused, right?

I think gcc doesn't complain, but clang does:

$ cat ttt.c
static inline void ret(void)
{
  return;
}

int main(void)
{
  return 0;
}

$ gcc  ttt.c  -Werror -Wunused-function
$ clang ttt.c  -Werror -Wunused-function
ttt.c:1:20: error: unused function 'ret' [-Werror,-Wunused-function]
    1 | static inline void ret(void)
      |                    ^~~
1 error generated.

>
> If you add -E to the cflags to get preprocessed output, can you confirm
> __sym_remove() is 'static inline'?

Yes, it is 'static inline'.

Song