These are fixes for the only three compiler warnings I encountered in my environment (macOS). I hope these are helpful.
This addresses the following warnings:
[ 50%] Building CXX object source/blender/io/alembic/CMakeFiles/bf_alembic.dir/exporter/abc_writer_hair.cc.o
/Users/linux_dr/blender-git/blender/source/blender/makesdna/intern/dna_defaults.c:190:1: warning: implicit conversion from 'int' to 'short' changes value from 53504 to -12032 [-Wconstant-conversion]
SDNA_DEFAULT_DECL_STRUCT(Mesh);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Users/linux_dr/blender-git/blender/source/blender/makesdna/intern/dna_defaults.c:139:56: note: expanded from macro 'SDNA_DEFAULT_DECL_STRUCT'
static const struct_name DNA_DEFAULT_##struct_name = _DNA_DEFAULT_##struct_name
^~~~~~~~~~~~~~~~~~~~~~~~~~
<scratch space>:97:1: note: expanded from here
_DNA_DEFAULT_Mesh
^~~~~~~~~~~~~~~~~
/Users/linux_dr/blender-git/blender/source/blender/makesdna/DNA_mesh_defaults.h:25:112: note: expanded from macro '_DNA_DEFAULT_Mesh'
.flag = ME_REMESH_REPROJECT_VOLUME | ME_REMESH_REPROJECT_PAINT_MASK | ME_REMESH_REPROJECT_SCULPT_FACE_SETS | ME_REMESH_REPROJECT_VERTEX_COLORS, \
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 warning generated.
[ 88%] Building C object source/blender/modifiers/CMakeFiles/bf_modifiers.dir/intern/MOD_shapekey.c.o
/Users/linux_dr/blender-git/blender/source/blender/blenkernel/intern/curve_to_mesh_convert.cc:671:21: warning: suggest braces around initialization of subobject [-Wmissing-braces]
Curves main_id = {nullptr};
^~~~~~~
{ }
/Users/linux_dr/blender-git/blender/source/blender/blenkernel/intern/curve_to_mesh_convert.cc:676:24: warning: suggest braces around initialization of subobject [-Wmissing-braces]
Curves profile_id = {nullptr};
^~~~~~~
{ }