In some places, spatialite uses functions that are excluded from compilation by OMIT_GEOS macro, which causes modern compilers (GCC-14+, Clang-17+) to complain about usage of implicitly defined functions.

gg_advanced.c:2308:21: error: implicit declaration of function 'gaiaSetGeosAuxErrorMsg_r'; did you mean 'gaiaSetProjErrorMsg_r'? [-Wimplicit-function-declaration]
 2308 |                     gaiaSetGeosAuxErrorMsg_r
      |                     ^~~~~~~~~~~~~~~~~~~~~~~~

We found it in Gentoo, in some test builds.
https://bugs.gentoo.org/919177
There's a working patch in consideration:
https://github.com/gentoo/gentoo/pull/40009/ files#diff-86b2f21989f30348df499f91b9f9f117d8aa16b2478759ca46136905eeafd149
Patch also includes fixes for missing PROJ.6 variants of threaded context creation function.