XCode 16.3 and “old” React Native Apps

Not even two years ago (late 2023 / early 2024), I wrote a bunch of mobile apps with the “latest” version of React Native (CJExplorer, Receiptopia) at the time.

The latest version of React Native at the time was 0.73.1. The latest veresion now (May 2025) is 0.79. Unless you’re a developer who does a lot of React Native programming every day, it’s unlikely you will try to upgrade to the latest and greatest all the time.

As many developers familiar with iOS development know, XCode has the habit of changing the standard libraries with XCode versions — sometimes even the minor version say from 16.2 to 16.3.

From the release notes of XCode 16.3:

The base template for std::char_traits has been removed. If you are using std::char_traits with types other than char, wchar_t, char8_t, char16_t, char32_t or a custom character type for which you specialized std::char_traits, your code will stop working. The Standard does not mandate that a base template is provided… blah blah blah justifications.

LOL, like WTF?

Anyway, because of this, all React Native apps based on React Native < 0.76 do not compile for iOS anymore.

React Native community provided an update for 0.76.x, but if you’re on < 0.76, you’re sort of out of luck.

There is no shortage of “solutions” on how to “fix” this

1. Medium article: https://medium.com/@diptimaya.patra/fix-for-react-native-build-is-not-working-when-xcode-is-upgraded-8498f15cc009
2. Someone even recorded a youtube video: https://www.youtube.com/watch?v=7glItCzH2FM

The “solutions” boil down to either a) upgrade your React Native version; or b) downgrade your xcode.

I also tried to “upgrade” my apps to a newer React Native. In fact, I spent almost a good 20 hours spread over a month to do that. Unfortunately, it’s simply not feasible because of all the dependencies the project have that make upgrades practically infeasible. (The apps do on-device vision / machine-learning / “AI” 🙄, and so they have a lot of native code dependencies).

The rest of this article describes a third solution, that hopefully it will help others. Basically you create a precompiled header that is used for compilation for all the dependencies for your React Native iOS app:

1. Update the pod file. Add:

prefix_header_path = File.join(Pod::Config.instance.installation_root, 'YourReactNativeApp/YourReactNativeApp-Prefix.pch')

and reference it

config.build_settings['GCC_PREFIX_HEADER'] = prefix_header_path

2. Add a .pch file with #ifdef to control when the missing template instantiation should come from:

#ifdef __cplusplus
#include <string>
#include <ios>
#include "custom_char_traits.h"
#endif

3. Create a .h file with the specialization (among other things) that’s now… deprecated..

template<>
struct std::char_traits<unsigned char> : yourreactnativeapp_traits::char_traits<unsigned char> {};

Full code example here: https://github.com/chuvincent/random-scripts/tree/main/xcode16_3-react-native

If this helped you, please add a star to the github repo!