This is a more detailed error report for #488.

When compiling for iOS or Apple silicon, two symbols are not defined:

Undefined symbols for architecture arm64:
  "_pixman_composite_over_n_8888_asm_neon", referenced from:
      color_SourceOver(unsigned int*, int, unsigned int, unsigned int) in vdrawhelper_neon.o
  "_pixman_composite_src_n_8888_asm_neon", referenced from:
      memfill32(unsigned int*, unsigned int, int) in vdrawhelper_neon.o
ld: symbol(s) not found for architecture arm64

The file that uses these functions is vdrawhelper_neon.cpp.

Steps to Reproduce:

1. Download rlottie source code on a Mac with Xcode installed.
2. Edit the root CMakeLists.txt to include set(CMAKE_OSX_ARCHITECTURES "x86_64;arm64" CACHE INTERNAL "") below the project line, this will enable building Apple Silicon:

cmake_minimum_required( VERSION 3.3 )

#declare project
project( rlottie VERSION 0.2 LANGUAGES C CXX ASM)
set(CMAKE_OSX_ARCHITECTURES "x86_64;arm64" CACHE INTERNAL "") # add this line
# ...

3. In the rlottie root directory, execute mkdir -p build; cd build; cmake -G "Xcode" ..
4. Open the Xcode project and try to build the rlottie library target.

Other Notes:
In the file pixman-arm-neon-asm.S (the file that contains the definitions for pixman_composite_over_n_8888_asm_neon and pixman_composite_src_n_8888_asm_neon), comments mention that there exists a C function fast_composite_over_8888_0565 in pixman-fast-path.c which implements an identical behavior to the arm assembly functions. Perhaps use that function instead in vdrawhelper_neon.cpp, when the target does not support the assembly implementation?