Regex operations return incorrect results when ARM Memory Tagging Extensions (MTE) are enabled

[mic-]

Boost version:
1.90.0. I've also seen this on 1.86.0, and don't think it's specific to any particular Boost version.

Test hardware:
Google Pixel 9

Test OS:
Android 16 QPR3 Beta 2 (build CP11.251209.007.A1).
This build seems to have MTE enabled system-wide by default. Can be verified under Settings>System>Developer options>Memory Tagging Extension.

Description:
Boost regex operation return incorrect results, e.g. boost::regex_match returns false in cases when it should return true.
This seems to occur when both of the following are true:

1. Memory Tagging Extensions are enabled.
2. A character type larger than 1 byte (e.g. wchar_t) is used.

Steps to reproduce:
I have prepared a minimal reproducible example.
In Android Studio, select New>New project...>Native C++, and complete the wizard.

Then replace the contents of the following files:

app/src/main/cpp/native-lib.cpp

#include <jni.h>
#include <string>
#include "boost/regex.hpp"

using CharT = wchar_t;
using String = std::basic_string<CharT>;

extern "C" JNIEXPORT jstring JNICALL
Java_com_example_boostregex16qpr3b2_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    String input = L"ABC";
    String pattern = L"^[A-Z]{1,100}$";  // Note: 99 and below as the upper bound works for some reason.

    boost::basic_regex<CharT, boost::cpp_regex_traits<CharT>> re;
    re.imbue(std::locale::classic());
    re.assign(pattern,boost::regex::perl);

    if (boost::regex_match(input, re)) {
        return env->NewStringUTF("OK");
    } else {
        return env->NewStringUTF("Fail");
    }
}

app/src/main/cpp/CMakeLists.txt

cmake_minimum_required(VERSION 3.22.1)

project("boostregex16qpr3b2")

set(BOOST_SRC_RELATIVE_PATH "" CACHE STRING "Path to the Boost source code, relative to app/src/main")
get_filename_component(BOOSTSRCROOT ../${BOOST_SRC_RELATIVE_PATH} ABSOLUTE)

set(CMAKE_CXX_STANDARD 20)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS OFF)

add_library(boost_headers INTERFACE)
target_include_directories(boost_headers INTERFACE ${BOOSTSRCROOT})

add_library(native-lib SHARED
        native-lib.cpp
)
target_compile_options(native-lib PUBLIC
        -funwind-tables -fomit-frame-pointer
        -fno-strict-aliasing
        -Wa,--noexecstack
)
target_link_options(native-lib PRIVATE "-Wl,-z,max-page-size=16384")
target_link_libraries(native-lib
        boost_headers
        android
        log)

app/build.gradle.kts

plugins {
    alias(libs.plugins.android.application)
    alias(libs.plugins.kotlin.android)
}

android {
    namespace = "com.example.boostregex16qpr3b2"
    compileSdk {
        version = release(36)
    }

    ndkVersion = "27.3.13750724"

    defaultConfig {
        applicationId = "com.example.boostregex16qpr3b2"
        minSdk = 28
        targetSdk = 35
        versionCode = 1
        versionName = "1.0"

        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                arguments(
                    "-DBOOST_SRC_RELATIVE_PATH=../../../../../../github/boost_1_90_0"
                )
            }
        }
    }

    buildTypes {
        release {
            isMinifyEnabled = false
            proguardFiles(
                getDefaultProguardFile("proguard-android-optimize.txt"),
                "proguard-rules.pro"
            )
        }
    }
    compileOptions {
        sourceCompatibility = JavaVersion.VERSION_11
        targetCompatibility = JavaVersion.VERSION_11
    }
    kotlinOptions {
        jvmTarget = "11"
    }
    externalNativeBuild {
        cmake {
            path = file("src/main/cpp/CMakeLists.txt")
            version = "3.22.1"
        }
    }
    buildFeatures {
        viewBinding = true
    }
}

dependencies {
    implementation(libs.androidx.core.ktx)
    implementation(libs.androidx.appcompat)
    implementation(libs.material)
    implementation(libs.androidx.constraintlayout)
    testImplementation(libs.junit)
    androidTestImplementation(libs.androidx.junit)
    androidTestImplementation(libs.androidx.espresso.core)
}

Running the resulting app on the aforementioned Test device/OS will display "Fail" on the screen, instead of the expected "OK".