Crash in libicucore via NSDateFormatter dateFromString: on iOS 26.2

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Introduction:

I’m encountering a consistent crash in production on iOS 26.2 (build 23C55). The crash occurs deep within libicucore when calling [NSDateFormatter dateFromString:].

Crash Summary:

Exception Type: SIGSEGV (SEGV_ACCERR)

Fault Address: 0xffffffff

Thread: Crashed on Main Thread (Thread 0)

Library: libicucore.A.dylib

Code Snippet:

The crash is triggered by the following method. It converts a string to an NSDate using a specific format and locale:

// 获取日期date
- (NSDate *)getDateWithTime:(NSString *)time formatter:(NSString *)formatterStr {
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:formatterStr];
    formatter.timeZone = [NSTimeZone timeZoneWithName:@"Asia/Shanghai"];
    formatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];
    return [formatter dateFromString:time];
}

Backtrace:

Here is the relevant part of the crash report:

Incident Identifier: E24485B6-C53E-4115-A6CF-A7E4A952AD50
CrashReporter Key:   21FAC1CF-F56B-409A-98AA-351D3D2EB06C
Hardware Model:      iPhone18,2
Code Type:       ARM-64
Parent Process:   [1]

Date/Time:       2026-01-12T01:32:25Z
OS Version:      iPhone OS 26.2 (23C55)
Report Version:  105
SDK Version:  0.0.4

Exception Type:  SIGSEGV
Exception Codes: SEGV_ACCERR at 0xffffffff
Crashed Thread:  0

Thread 0 Crashed:
0   libicucore.A.dylib                   0x000000019b81def8 0x19b74a000 + 868088
1   libicucore.A.dylib                   0x000000019b7da91c 0x19b74a000 + 592156
2   libicucore.A.dylib                   0x000000019b8d8340 0x19b74a000 + 1631040
3   libicucore.A.dylib                   0x000000019b8eae18 0x19b74a000 + 1707544
4   libicucore.A.dylib                   0x000000019b8eb600 0x19b74a000 + 1709568
5   libicucore.A.dylib                   0x000000019b878be4 0x19b74a000 + 1240036
6   libicucore.A.dylib                   0x000000019b87ae84 0x19b74a000 + 1248900
7   libicucore.A.dylib                   0x000000019b87b2dc 0x19b74a000 + 1250012
8   libicucore.A.dylib                   0x000000019b9564ac 0x19b74a000 + 2147500
9   libicucore.A.dylib                   0x000000019b954afc 0x19b74a000 + 2140924
10  libicucore.A.dylib                   0x000000019b952794 0x19b74a000 + 2131860
11  libicucore.A.dylib                   0x000000019b98689c 0x19b74a000 + 2345116
12  CoreFoundation                       0x00000001895dbfe0 0x18953d000 + 651232
13  CoreFoundation                       0x00000001895dbaa0 0x18953d000 + 649888
14  Foundation                           0x0000000186d2029c 0x186b88000 + 1671836
15  Foundation                           0x00000001874a62dc 0x186b88000 + 9560796
16  Foundation                           0x00000001874a6384 0x186b88000 + 9560964
17  xxxx                               0x0000000105ea6e30 -[xxxxx getDateWithTime:formatter:] + 168

and

Thread 0 crashed with ARM-64 Thread State:
    pc: 0x000000019b81def8     fp: 0x000000016f96bc10     sp: 0x000000016f96bbd0     x0: 0x00000000ffffffff 
    x1: 0x000000019ba1e8e0     x2: 0x0000000000000002     x3: 0x000000000000000b     x4: 0x0000000000000074 
    x5: 0x0000000000000069     x6: 0x0000000000000000     x7: 0xfffff0003ffff800     x8: 0x000000009ba18014 
    x9: 0x00000001148dffd0    x10: 0x0000000000000002    x11: 0x0000000000000004    x12: 0x0000000000000220 
   x13: 0x0000000000000030    x14: 0x000000015b6f36b8    x15: 0x000000015cfe0000    x16: 0x00000002a19d0ff0 
   x17: 0x00000001f5590a70    x18: 0x0000000000000000    x19: 0x000000016f96bc30    x20: 0x0000000000000000 
   x21: 0x000000015cfe3200    x22: 0x000000019ba18014    x23: 0x0000000000000000    x24: 0x000000015cfe32a0 
   x25: 0x0000000000000003    x26: 0x0000000000000000    x27: 0x0000000000000000    x28: 0x000000015cfe3200 
    lr: 0x000000019b7da958   cpsr: 0x00000000a0000000

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