CMake multi-module shared library build does not build with -Wl,-z,defs and -Wl,--no-undefined,--no-allow-shlib-undefined on Linux

[ADKaster]

I'm trying to start building my project with all of -z,defs, --no-undefined and --no-allow-shlib-undefined on ELF platforms.

I'm pulling in swift-collections via FetchContent.

libDequeModule.so fails to link with an "undefined symbol: ceil" error when linking with lld from a main-snapshot.

Information

• Package version: 1.1.2
• Platform version: Ubuntu 24.04
• Swift version: Swift version 6.2-dev (LLVM 1b38440e27d7b93, Swift 0a9ab413a091180)
• Swiftly list output: main-snapshot-2024-12-16 (in use)

Checklist

• If possible, I've reproduced the issue using the main branch of this package.
• I've searched for existing GitHub issues.

Steps to Reproduce

Create a directory with the following CMakeLists.txt

CMakeLists.txt

cmake_minimum_required(VERSION 3.31)

project(example LANGUAGES Swift CXX)

macro(add_cxx_compile_options)
  set(args "")
  foreach(arg ${ARGN})
    string(APPEND args ${arg}$<SEMICOLON>)
    add_compile_options("SHELL:$<$<COMPILE_LANGUAGE:Swift>:-Xcc ${arg}>")
  endforeach()
  add_compile_options($<$<COMPILE_LANGUAGE:C,CXX,ASM>:${args}>)
endmacro()

set(BUILD_SHARED_LIBS ON)

if (NOT WIN32 AND NOT APPLE)
    # NOTE: Assume ELF
    add_link_options(LINKER:-z,defs)
    add_link_options(LINKER:--no-undefined)
    add_link_options(LINKER:--no-allow-shlib-undefined)
endif()

include(FetchContent)

set(FETCHCONTENT_TRY_FIND_PACKAGE_MODE OPT_IN)
FetchContent_Declare(SwiftCollections
    GIT_REPOSITORY https://github.com/apple/swift-collections.git
    GIT_TAG main
    OVERRIDE_FIND_PACKAGE
)

FetchContent_MakeAvailable(SwiftCollections)

Generate a build:

cmake -Bbuild -GNinja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++

Run the build:

ninja -C build

Expected behavior

Successful build of all the swift-collections modules

Actual behavior

andrew@Andrew-Workstation:~/ladybird-org/testing/swift-tests/swift-collections-no-undefined$ cmake -Bbuild -GNinja -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
-- The Swift compiler identification is Apple 6.2
-- The CXX compiler identification is Clang 17.0.0
-- Check for working Swift compiler: /home/andrew/.local/bin/swiftc
-- Check for working Swift compiler: /home/andrew/.local/bin/swiftc - works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /home/andrew/.local/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
Cloning into 'swiftcollections-src'...
Already on 'main'
Your branch is up to date with 'origin/main'.
-- The C compiler identification is Clang 17.0.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /home/andrew/.local/bin/clang - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Configuring done (2.9s)
-- Generating done (0.0s)
-- Build files have been written to: /home/andrew/ladybird-org/testing/swift-tests/swift-collections-no-undefined/build
andrew@Andrew-Workstation:~/ladybird-org/testing/swift-tests/swift-collections-no-undefined$ ninja -C build/
ninja: Entering directory `build/'
[6/16] Building Swift Module 'DequeModule' with 17 sources
/home/andrew/ladybird-org/testing/swift-tests/swift-collections-no-undefined/build/_deps/swiftcollections-src/Sources/DequeModule/Deque+Collection.swift:26:18: warning: stored property '_storage' of 'Sendable'-conforming struct 'Iterator' has non-sendable type 'Deque<Element>._Storage'; this is an error in the Swift 6 language mode
 24 |   public struct Iterator: IteratorProtocol {
 25 |     @usableFromInline
 26 |     internal var _storage: Deque._Storage
    |                  `- warning: stored property '_storage' of 'Sendable'-conforming struct 'Iterator' has non-sendable type 'Deque<Element>._Storage'; this is an error in the Swift 6 language mode
 27 | 
 28 |     @usableFromInline

/home/andrew/ladybird-org/testing/swift-tests/swift-collections-no-undefined/build/_deps/swiftcollections-src/Sources/DequeModule/Deque._Storage.swift:15:10: note: consider making struct '_Storage' conform to the 'Sendable' protocol
 13 |   @frozen
 14 |   @usableFromInline
 15 |   struct _Storage {
    |          `- note: consider making struct '_Storage' conform to the 'Sendable' protocol
 16 |     @usableFromInline
 17 |     internal typealias _Buffer = ManagedBufferPointer<_DequeBufferHeader, Element>
/home/andrew/ladybird-org/testing/swift-tests/swift-collections-no-undefined/build/_deps/swiftcollections-src/Sources/DequeModule/Deque+Collection.swift:26:18: warning: stored property '_storage' of 'Sendable'-conforming struct 'Iterator' has non-sendable type 'Deque<Element>._Storage'; this is an error in the Swift 6 language mode
 24 |   public struct Iterator: IteratorProtocol {
 25 |     @usableFromInline
 26 |     internal var _storage: Deque._Storage
    |                  `- warning: stored property '_storage' of 'Sendable'-conforming struct 'Iterator' has non-sendable type 'Deque<Element>._Storage'; this is an error in the Swift 6 language mode
 27 | 
 28 |     @usableFromInline

/home/andrew/ladybird-org/testing/swift-tests/swift-collections-no-undefined/build/_deps/swiftcollections-src/Sources/DequeModule/Deque._Storage.swift:15:10: note: consider making struct '_Storage' conform to the 'Sendable' protocol
 13 |   @frozen
 14 |   @usableFromInline
 15 |   struct _Storage {
    |          `- note: consider making struct '_Storage' conform to the 'Sendable' protocol
 16 |     @usableFromInline
 17 |     internal typealias _Buffer = ManagedBufferPointer<_DequeBufferHeader, Element>
[8/16] Linking Swift shared library lib/libDequeModule.so
FAILED: lib/libDequeModule.so 
: && /home/andrew/.local/bin/swiftc -j 32 -num-threads 32 -emit-library   -Xlinker -z -Xlinker defs -Xlinker --no-undefined -Xlinker --no-allow-shlib-undefined  -Xlinker -soname -Xlinker libDequeModule.so -o lib/libDequeModule.so _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+Codable.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+Collection.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+CustomReflectable.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+Descriptions.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+Equatable.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+ExpressibleByArrayLiteral.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+Extras.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+Hashable.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+Sendable.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque+Testing.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque._Storage.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque._UnsafeHandle.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/_DequeBuffer.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/_DequeBufferHeader.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/_DequeSlot.swift.o _deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/_UnsafeWrappedBuffer.swift.o -L /home/andrew/ladybird-org/testing/swift-tests/swift-collections-no-undefined/build/lib -Xlinker -rpath -Xlinker /home/andrew/ladybird-org/testing/swift-tests/swift-collections-no-undefined/build/lib:  lib/libInternalCollectionsUtilities.so && :
error: link command failed with exit code 1 (use -v to see invocation)
_deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque._Storage.swift.o:Deque._Storage.swift.o:function $s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF:(.text.$s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF+0x208): error: undefined reference to 'round'
_deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque._Storage.swift.o:Deque._Storage.swift.o:function $s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF:(.text.$s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF+0x21f): error: undefined reference to 'rint'
_deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque._Storage.swift.o:Deque._Storage.swift.o:function $s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF:(.text.$s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF+0x233): error: undefined reference to 'trunc'
_deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque._Storage.swift.o:Deque._Storage.swift.o:function $s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF:(.text.$s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF+0x261): error: undefined reference to 'ceil'
_deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque._Storage.swift.o:Deque._Storage.swift.o:function $s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF:(.text.$s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF+0x275): error: undefined reference to 'floor'
_deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque._Storage.swift.o:Deque._Storage.swift.o:function $s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF:(.text.$s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF+0x2e3): error: undefined reference to 'ceil'
_deps/swiftcollections-build/Sources/DequeModule/CMakeFiles/DequeModule.dir/Deque._Storage.swift.o:Deque._Storage.swift.o:function $s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF:(.text.$s11DequeModule0A0V8_StorageV13_growCapacity2to8linearlyS2i_SbtF+0x2f7): error: undefined reference to 'floor'
clang: error: linker command failed with exit code 1 (use -v to see invocation)
[11/16] Building Swift Module 'HashTreeCollections' with 85 sources
ninja: build stopped: subcommand failed.

Failed link due to missing libm symbols. Adding a link_libraries(m) before FetchContent_MakeAvailable fixes the issue.

[ADKaster]

If a BUILD_SHARED_LIBS=ON config on linux is not supported, then this can be worked around by explicitly setting it to off for SwiftCollections like so:

set(BUILD_SHARED_LIBS_SAVE ${BUILD_SHARED_LIBS})
set(BUILD_SHARED_LIBS OFF)

FetchContent_MakeAvailable(SwiftCollections)

set(BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS_SAVE})

[lorentey]

The CMake configuration in this package is for compiling this code while building the Swift toolchain itself, while SwiftPM is not available. Other use is also okay, of course -- just keep in mind that this is not a stable feature; things may break with each new tag.

Patches fixing things outside of toolchain builds are welcome, too! But the configuration must keep working for that use case, no matter what.

[ADKaster]

Does that mean that swift-collections will be available as a dependency shipped with the toolchain for "external" consumers to use in the future? Similar to how swift-testing is handled?

Or is it more that external consumers of the library are expected to use SwiftPM rather than CMake to build swift-collections for their own projects? Until and unless it becomes easy to call into SwiftPM via e.g. ExternalProject with a handy wrapper CMake script to obtain dependencies for mixed Swift/C++ targets to link to, I don't think that's going to work for my project 😅.