[PATCH] build: fix linker warnings about undefined symbols

[Tyler Retzlaff]

On Wed, Jan 10, 2024 at 03:01:03PM +0000, Bruce Richardson wrote:
> The default behaviour of "ld.lld" has changed, so it now prints out
> warnings about entries in the version.map file which don't exist in
> the current build. Since we use our version.map file simply to filter
> out the functions we don't want made public, we include in it all
> functions across all OS's and builds that we want public if present.
> This causes these ld warnings to be emitted, e.g. on BSD, which is
> missing functionality found on Linux. For example:
> 
> * hpet functions in EAL
> * regexdev enqueue and dequeue burst
> * eventdev event_timer functions
> 
> Easiest solution, without major rework of how we use our version.map
> files, and without dynamically generating them per-build, is to pass
> the --undefined-version flag to the linker, to restore the old
> behaviour.
> 
> Signed-off-by: Bruce Richardson <bruce.richardson at intel.com>
> ---

Acked-by: Tyler Retzlaff <roretzla at linux.microsoft.com>

i don't know if has ever been discussed but a way to achieve a similar
outcome would be to introduce a visibility macro allowing the data and
function symbols to be explicitly made visible while making the build
default hidden.

https://gcc.gnu.org/wiki/Visibility

on windows symbols are hidden by default (opposite of gnu toolchain) and
allowing the symbols that are intended to be public be annotated in code
with a macro instead of a separate map/def file would arguably appear
more consistent.  additionally, the current process of converting a map
file to a def file for windows has limitations with respect to things
like marking the type of symbol being exported.

ty