-- Force libc++ to use name-based type_info comparison.  On FreeBSD/Clang the
-- default compares type_info object addresses, but the same C++ class
-- template instantiations are emitted into both libdwave-optimization.so and
-- each Cython extension module, producing distinct type_info objects for the
-- same type.  This breaks cross-DSO std::type_index lookups and dynamic_cast.
-- The "non-unique" implementation compares mangled type names, so types match
-- across shared libraries.

--- meson.build.orig	2026-07-23 19:58:12 UTC
+++ meson.build
@@ -22,6 +22,17 @@ add_project_arguments(['-g1'], language: ['cpp'])
 # We want some debugging symbols
 add_project_arguments(['-g1'], language: ['cpp'])
 
+# On FreeBSD/Clang libc++ defaults to comparing type_info object addresses. The
+# same C++ class template instantiations are emitted into both
+# libdwave-optimization.so and the individual Cython extension modules, so
+# each shared object gets its own type_info copy and cross-DSO dynamic_cast
+# and std::type_index lookups fail. Force the "non-unique" implementation,
+# which compares mangled type names, so types match across shared libraries.
+add_project_arguments(
+    '-D_LIBCPP_TYPEINFO_COMPARISON_IMPLEMENTATION=2',
+    language: 'cpp',
+)
+
 cpp = meson.get_compiler('cpp')
 py = import('python').find_installation(pure: false)