[pacman-dev] [PATCH 3/3] meson: use hidden symbol visiblity by default

[Emil Velikov]

On Thu, 24 Dec 2020 at 01:38, Eli Schwartz <eschwartz at archlinux.org> wrote:
>
> On 12/23/20 5:42 PM, Emil Velikov wrote:
> > All the required public API is annotated with SYMEXPORT, so we can just
> > add the meson notation, to hide all the symbols by default.
> >
> > Thus we no longer spill all the internal API into the global namespace.
> Thanks for noticing this... it's a regression from autotools, which
> contained in lib/libalpm/Makefile.am:
>
> if ENABLE_VISIBILITY_CC
> if DARWIN
> AM_CFLAGS += -fvisibility=hidden
> else
> AM_CFLAGS += -fvisibility=internal
> endif
> endif
>
>
> I wonder if we had a good reason to use "internal" and if we should
> continue to do so? IIUC it makes it slightly more optimized at the cost
> of allowing pointers into private functions (e.g. callbacks) used by
> other programs to segfault.
>
If the output of size&ls is any indication - there is little-to-no
optimisation happening.
The former produces the same numbers, while the latter claims that
binaries built with "internal" are larger by 8 bytes (always).

Fwiw the above snippet is the first time I've seen anyone using
"internal", after staring at various projects for 5+ years.
Can bring it back, simply not sure it brings much.

Thanks
Emil

$ ls
812336 build-internal/libalpm.so.12.0.1
812328 build-hidden/libalpm.so.12.0.1
337176 build-internal/pacman
337168 build-hidden/pacman

$ size
316708    3080     592  320380   4e37c build-internal/libalpm.so.12.0.1
316708    3080     592  320380   4e37c build-hidden/libalpm.so.12.0.1
155288    5040    5808  166136   288f8 build-internal/pacman
155288    5040    5808  166136   288f8 build-hidden/pacman