Troubleshooting
Fixes for known build and runtime issues
iOS linker error: DebugStringConvertible / Sealable undefined symbols (RN 0.84+)
On React Native 0.84 and newer, iOS links against a prebuilt React core framework by default. Its Release flavor is compiled with NDEBUG, which removes debug-only C++ symbols like facebook::react::DebugStringConvertible and facebook::react::Sealable. When the prebuilt core on disk doesn't match your build configuration (stale Pods/ state, an interrupted build, or a CocoaPods cache carrying over an old extraction), every Fabric library built from source fails to link with errors like:
Undefined symbols for architecture arm64:
"facebook::react::Sealable::Sealable()", referenced from:
facebook::react::NFMaskedViewProps::NFMaskedViewProps() in libNFMaskedView.a(NFMaskedViewComponentView.o)This is not specific to @rednegniw/masked-view: the same error hits any from-source Fabric component (it's just often the first one in an otherwise JS-only app). To fix it, reset the pods state so the correct core flavor is re-extracted:
cd ios
rm -rf Pods build
pod installThen clean the build folder in Xcode (Product > Clean Build Folder) and rebuild.
Don't work around this by defining REACT_NATIVE_PRODUCTION=1 in your Podfile. It silences the linker error but creates an ABI mismatch in ViewProps that crashes at runtime. Also make sure your Podfile calls react_native_post_install(installer, ...) in post_install; it aligns compiler flags with the prebuilt core in Release builds.