Error when cross-compiling Swift package with Cxx interop enabled with Swift 6.2

Development C++ interoperability
1

I've compiled Swift for armv7 and have had success building the CxxStdlib module for versions since 5.10 up to 6.1.2. However, when I switch to a nightly 6.2 or development snapshot, I get this error when trying to compile a Swift package with Cxx interop enabled:

/src/sysroot-debian-bookworm/usr/lib/swift/linux/Glibc.swiftmodule/armv7-unknown-linux-gnueabihf.private.swiftinterface:92:44: error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 90 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt, _ ptr: Swift.UnsafeMutableRawPointer) -> Swift.CInt
 91 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt) -> Swift.CInt
 92 | public typealias sighandler_t = SwiftGlibc.__sighandler_t
    |                                            `- error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 93 | #if compiler(>=5.3) && $NonescapableTypes
 94 | public var SIG_DFL: Glibc.sighandler_t? {

/src/sysroot-debian-bookworm/usr/include/signal.h:72:16: note: type alias declared here
 70 | 
 71 | /* Type of a signal handler.  */
 72 | typedef void (*__sighandler_t) (int);
    |                `- note: type alias declared here
 73 | 
 74 | /* The X/Open definition of `signal' specifies the SVID semantic.  Use

/src/sysroot-debian-bookworm/usr/lib/swift/linux/Glibc.swiftmodule/armv7-unknown-linux-gnueabihf.private.swiftinterface:1:1: error: failed to build module 'Glibc' for importation due to the errors above; the textual interface may be broken by project issues or a compiler bug
  1 | // swift-interface-format-version: 1.0
    | `- error: failed to build module 'Glibc' for importation due to the errors above; the textual interface may be broken by project issues or a compiler bug
  2 | // swift-compiler-version: Swift version 6.2-dev effective-5.10 (LLVM 367909f98241076, Swift 1aab25d9909cc47)
  3 | // swift-module-flags: -target armv7-unknown-linux-gnueabihf -disable-objc-interop -autolink-force-load -enable-library-evolution -module-link-name swiftGlibc -static -swift-version 5 -O -library-level api -enforce-exclusivity=unchecked -disable-objc-interop -target-min-inlining-version min -enable-experimental-feature NoncopyableGenerics2 -enable-experimental-feature SuppressedAssociatedTypes -enable-experimental-feature SE427NoInferenceOnExtension -enable-experimental-feature NonescapableTypes -enable-experimental-feature LifetimeDependence -enable-experimental-feature InoutLifetimeDependence -enable-experimental-feature LifetimeDependenceMutableAccessors -enable-upcoming-feature MemberImportVisibility -module-name Glibc

/src/sysroot-debian-bookworm/usr/lib/swift/linux/Glibc.swiftmodule/armv7-unknown-linux-gnueabihf.private.swiftinterface:92:44: error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 90 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt, _ ptr: Swift.UnsafeMutableRawPointer) -> Swift.CInt
 91 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt) -> Swift.CInt
 92 | public typealias sighandler_t = SwiftGlibc.__sighandler_t
    |                                            `- error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 93 | #if compiler(>=5.3) && $NonescapableTypes
 94 | public var SIG_DFL: Glibc.sighandler_t? {

/src/sysroot-debian-bookworm/usr/include/signal.h: 0:
/src/sysroot-debian-bookworm/usr/lib/swift/linux/Glibc.swiftmodule/armv7-unknown-linux-gnueabihf.private.swiftinterface:92:44: error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 90 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt, _ ptr: Swift.UnsafeMutableRawPointer) -> Swift.CInt
 91 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt) -> Swift.CInt
 92 | public typealias sighandler_t = SwiftGlibc.__sighandler_t
    |                                            `- error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 93 | #if compiler(>=5.3) && $NonescapableTypes
 94 | public var SIG_DFL: Glibc.sighandler_t? {

/src/sysroot-debian-bookworm/usr/include/signal.h:72:16: note: type alias declared here
 70 | 
 71 | /* Type of a signal handler.  */
 72 | typedef void (*__sighandler_t) (int);
    |                `- note: type alias declared here
 73 | 
 74 | /* The X/Open definition of `signal' specifies the SVID semantic.  Use

/src/sysroot-debian-bookworm/usr/lib/swift/linux/Synchronization.swiftmodule/armv7-unknown-linux-gnueabihf.private.swiftinterface: 0:
/src/sysroot-debian-bookworm/usr/lib/swift/linux/Glibc.swiftmodule/armv7-unknown-linux-gnueabihf.private.swiftinterface:92:44: error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 90 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt, _ ptr: Swift.UnsafeMutableRawPointer) -> Swift.CInt
 91 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt) -> Swift.CInt
 92 | public typealias sighandler_t = SwiftGlibc.__sighandler_t
    |                                            `- error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 93 | #if compiler(>=5.3) && $NonescapableTypes
 94 | public var SIG_DFL: Glibc.sighandler_t? {

/src/sysroot-debian-bookworm/usr/include/signal.h: 0:
/src/sysroot-debian-bookworm/usr/lib/swift/linux/Glibc.swiftmodule/armv7-unknown-linux-gnueabihf.private.swiftinterface:92:44: error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 90 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt, _ ptr: Swift.UnsafeMutableRawPointer) -> Swift.CInt
 91 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt) -> Swift.CInt
 92 | public typealias sighandler_t = SwiftGlibc.__sighandler_t
    |                                            `- error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 93 | #if compiler(>=5.3) && $NonescapableTypes
 94 | public var SIG_DFL: Glibc.sighandler_t? {

/src/sysroot-debian-bookworm/usr/include/signal.h: 0:
/src/sysroot-debian-bookworm/usr/lib/swift/linux/Synchronization.swiftmodule/armv7-unknown-linux-gnueabihf.private.swiftinterface: 0:
/src/sysroot-debian-bookworm/usr/lib/swift/linux/Glibc.swiftmodule/armv7-unknown-linux-gnueabihf.private.swiftinterface:92:44: error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 90 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt, _ ptr: Swift.UnsafeMutableRawPointer) -> Swift.CInt
 91 | public func ioctl(_ fd: Swift.CInt, _ request: Swift.UInt) -> Swift.CInt
 92 | public typealias sighandler_t = SwiftGlibc.__sighandler_t
    |                                            `- error: cannot use type alias '__sighandler_t' here; C++ types from imported module 'SwiftGlibc' do not support library evolution
 93 | #if compiler(>=5.3) && $NonescapableTypes
 94 | public var SIG_DFL: Glibc.sighandler_t? {

/src/sysroot-debian-bookworm/usr/include/signal.h: 0:

Any ideas where these error would come from? Is this an indication of maybe the CxxStdlib module not compiling correctly?

2

Seems like we hit the same issue here: Bug: C++ types from imported module '__ObjC' do not support library evolution · Issue #696 · mrousavy/nitro · GitHub

3

I’m not so sure it’s the same issue. I’m compiling with swift build and on Linux to boot. I found that just doing import Foundation and cross compiling with a 6.2 Swift SDK causes the issue above. I’ve created a bug on swift-package-manager: