Static Linux SDK: `SIGSEGV: invalid address` when concurrently creating `Calendar` instances.

[barnard-b]

Creating instances of Calendar concurrently on Linux (Static SDK) reliably results in a segmentation fault. It occurs in both debug and release configurations. The same code runs without issue on macOS.

Host: macOS 15.2 (24C101), Xcode 16.2 (16C5032a)
Swift: Apple Swift version 6.0.3 (swift-6.0.3-RELEASE), arm64-apple-macosx15.0
Static Linux SDK: swift-6.0.3-RELEASE_static-linux-0.0.1
Target: Alma Linux 8.10 (x86_64 Static SDK)

FoundationTest.swift

import Foundation

@main
struct App {
    static func main() async throws {
        await withTaskGroup(of: Void.self) { group in
            for _ in 0...1_000_000 {
                group.addTask {
                    _ = Calendar(identifier: .gregorian)
                }
            }
        }
    }
}

Package.swift

// swift-tools-version: 6.0

import PackageDescription

let package = Package(
    name: "FoundationTest",
    platforms: [
        .macOS(.v12)
    ],
    targets: [
        .executableTarget(name: "FoundationTest")
    ]
)

Build for Linux

xcrun --toolchain swift swift build --swift-sdk x86_64-swift-linux-musl

Build for macOS

xcrun --toolchain swift swift build

Core Dump (Linux)

Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00000000007df69a in swift_isUniquelyReferenced_nonNull_native ()
[Current thread is 1 (LWP 11637)]
(gdb) bt
#0  0x00000000007df69a in swift_isUniquelyReferenced_nonNull_native ()
#1  0x0000000000a6ae14 in $sSD8_VariantV8setValue_6forKeyyq_n_xtFSi_20FoundationEssentials17_TimeZoneProtocol_pTg5Tf4enn_n ()
#2  0x0000000000a66908 in $s20FoundationEssentials13TimeZoneCacheV5StateV011findCurrentcD0AA0cD0VyF ()
#3  0x0000000000a68ead in $s20FoundationEssentials13TimeZoneCacheV7defaultAA0cD0VvgAfC5StateVzYbXEfU_ ()
#4  0x000000000089d50f in $s20FoundationEssentials11LockedStateV8withLockyqd__qd__xzYbKXEKlF ()
#5  0x0000000000a68e79 in $s20FoundationEssentials13TimeZoneCacheV7currentAA0cD0VvgTm ()
#6  0x0000000000a6484d in $s20FoundationEssentials8TimeZoneV7defaultACSgvgZ ()
#7  0x00000000008bab78 in $s20FoundationEssentials18_CalendarGregorianC10identifier8timeZone6locale12firstWeekday22minimumDaysInFirstWeek18gregorianStartDateAcA0C0V10IdentifierO_AA04TimeG0VSgAA6LocaleVSgSiSgAtA0R0VSgtcfcTf4dnnnnnn_n ()
#8  0x00000000008b9b01 in $s20FoundationEssentials18_CalendarGregorianCAA01_C8ProtocolA2aDP10identifier8timeZone6locale12firstWeekday22minimumDaysInFirstWeek18gregorianStartDatexAA0C0V10IdentifierO_AA04TimeH0VSgAA6LocaleVSgSiSgAvA0S0VSgtcfCTW ()
#9  0x000000000089b388 in $s20FoundationEssentials13CalendarCacheV5fixedyAA01_C8Protocol_pAA0C0V10IdentifierOFAaE_pAC5StateVzYbXEfU_TA ()
#10 0x000000000089d50f in $s20FoundationEssentials11LockedStateV8withLockyqd__qd__xzYbKXEKlF ()
#11 0x000000000089a15f in $s20FoundationEssentials13CalendarCacheV5fixedyAA01_C8Protocol_pAA0C0V10IdentifierOF ()
#12 0x0000000000891311 in $s20FoundationEssentials8CalendarV10identifierA2C10IdentifierOh_tcfC ()
#13 0x00000000004103e3 in $s14FoundationTest3AppV4mainyyYaKFZyScGyytGzYaXEfU_yyYacfU_TY0_ ()
#14 0x00000000008612e3 in swift::runJobInEstablishedExecutorContext(swift::Job*) ()
#15 0x0000000000862085 in swift_job_run ()
#16 0x000000000087634c in _dispatch_continuation_pop ()
#17 0x00000000008761b9 in _dispatch_async_redirect_invoke ()
#18 0x000000000087f8c6 in _dispatch_worker_thread ()
#19 0x0000000000b7f0cb in start ()
#20 0x0000000000000000 in ?? ()

LLDB (Linux)

Run 1:

Process 11086 stopped
* thread #4, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x00000000007df69a FoundationTest`swift_isUniquelyReferenced_nonNull_native [inlined] swift::RefCountBitsT<(swift::RefCountInlinedness)1> std::__1::__cxx_atomic_load[abi:hn170006]<swift::RefCountBitsT<(__a=0x8000000000000008, __order=memory_order_consume)1>>(std::__1::__cxx_atomic_base_impl<swift::RefCountBitsT<(swift::RefCountInlinedness)1>> const*, std::__1::memory_order) at cxx_atomic_impl.h:363:12
  thread #7, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x00000000004543f4 FoundationTest`$ss22__RawDictionaryStorageC4findys10_HashTableV6BucketV6bucket_Sb5foundtxSHRzlFSi_Tg5 at DictionaryStorage.swift:0
Note: this address is compiler-generated code in function $ss22__RawDictionaryStorageC4findys10_HashTableV6BucketV6bucket_Sb5foundtxSHRzlFSi_Tg5 that has no source code associated with it.
  thread #10, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x00000000007df69a FoundationTest`swift_isUniquelyReferenced_nonNull_native [inlined] swift::RefCountBitsT<(swift::RefCountInlinedness)1> std::__1::__cxx_atomic_load[abi:hn170006]<swift::RefCountBitsT<(__a=0x8000000000000008, __order=memory_order_consume)1>>(std::__1::__cxx_atomic_base_impl<swift::RefCountBitsT<(swift::RefCountInlinedness)1>> const*, std::__1::memory_order) at cxx_atomic_impl.h:363:12

Run 2:

Process 11128 stopped
* thread #2, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x0000000000a669fe FoundationTest`$sSDyq_SgxcigSi_20FoundationEssentials17_TimeZoneProtocol_pTg5 at <compiler-generated>:0
Note: this address is compiler-generated code in function $sSDyq_SgxcigSi_20FoundationEssentials17_TimeZoneProtocol_pTg5 that has no source code associated with it.
  thread #4, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x0000000000a669fe FoundationTest`$sSDyq_SgxcigSi_20FoundationEssentials17_TimeZoneProtocol_pTg5 at <compiler-generated>:0
Note: this address is compiler-generated code in function $sSDyq_SgxcigSi_20FoundationEssentials17_TimeZoneProtocol_pTg5 that has no source code associated with it.
  thread #5, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x0000000000a669fe FoundationTest`$sSDyq_SgxcigSi_20FoundationEssentials17_TimeZoneProtocol_pTg5 at <compiler-generated>:0
Note: this address is compiler-generated code in function $sSDyq_SgxcigSi_20FoundationEssentials17_TimeZoneProtocol_pTg5 that has no source code associated with it.
  thread #6, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x00000000007df69a FoundationTest`swift_isUniquelyReferenced_nonNull_native [inlined] swift::RefCountBitsT<(swift::RefCountInlinedness)1> std::__1::__cxx_atomic_load[abi:hn170006]<swift::RefCountBitsT<(__a=0x8000000000000008, __order=memory_order_consume)1>>(std::__1::__cxx_atomic_base_impl<swift::RefCountBitsT<(swift::RefCountInlinedness)1>> const*, std::__1::memory_order) at cxx_atomic_impl.h:363:12
  thread #7, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x00000000007df69a FoundationTest`swift_isUniquelyReferenced_nonNull_native [inlined] swift::RefCountBitsT<(swift::RefCountInlinedness)1> std::__1::__cxx_atomic_load[abi:hn170006]<swift::RefCountBitsT<(__a=0x8000000000000008, __order=memory_order_consume)1>>(std::__1::__cxx_atomic_base_impl<swift::RefCountBitsT<(swift::RefCountInlinedness)1>> const*, std::__1::memory_order) at cxx_atomic_impl.h:363:12
  thread #9, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x00000000007df69a FoundationTest`swift_isUniquelyReferenced_nonNull_native [inlined] swift::RefCountBitsT<(swift::RefCountInlinedness)1> std::__1::__cxx_atomic_load[abi:hn170006]<swift::RefCountBitsT<(__a=0x8000000000000008, __order=memory_order_consume)1>>(std::__1::__cxx_atomic_base_impl<swift::RefCountBitsT<(swift::RefCountInlinedness)1>> const*, std::__1::memory_order) at cxx_atomic_impl.h:363:12
  thread #10, name = 'FoundationTest', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)
    frame #0: 0x0000000000a669fe FoundationTest`$sSDyq_SgxcigSi_20FoundationEssentials17_TimeZoneProtocol_pTg5 at <compiler-generated>:0
Note: this address is compiler-generated code in function $sSDyq_SgxcigSi_20FoundationEssentials17_TimeZoneProtocol_pTg5 that has no source code associated with it.

[barnard-b]

Slightly different core dump from the full program:

#0  0x00000000027b8dfa in swift_isUniquelyReferenced_nonNull_native ()
#1  0x0000000002e82873 in $sSD8_VariantV8setValue_6forKeyyq_n_xtF20FoundationEssentials8CalendarV10IdentifierO_AE01_H8Protocol_pTg5Tf4enn_n ()
#2  0x0000000002e82c1a in $s20FoundationEssentials13CalendarCacheV5fixedyAA01_C8Protocol_pAA0C0V10IdentifierOFAaE_pAC5StateVzYbXEfU_TA ()
#3  0x0000000002e84d7f in $s20FoundationEssentials11LockedStateV8withLockyqd__qd__xzYbKXEKlF ()
#4  0x0000000002e819cf in $s20FoundationEssentials13CalendarCacheV5fixedyAA01_C8Protocol_pAA0C0V10IdentifierOF ()
#5  0x0000000002e7c471 in $s20FoundationEssentials8CalendarV10identifierA2C10IdentifierOh_tcfC ()
#6  0x0000000000eeacfb in <my app>
#7  0x000000000283aaa3 in swift::runJobInEstablishedExecutorContext(swift::Job*) ()
#8  0x000000000283ba15 in swift_job_run ()
#9  0x00000000028f11dc in _dispatch_continuation_pop ()
#10 0x00000000028f1049 in _dispatch_async_redirect_invoke ()
#11 0x00000000028fa756 in _dispatch_worker_thread ()
#12 0x00000000035c2cbb in start ()
#13 0x0000000000000000 in ?? ()