build: Set shared linker flags in toolchain file #31395

1. 
   TheCharlatan commented at 10:34 am on November 30, 2024: contributor

   These are required when cross-compiling shared libraries such as the kernel library.

   This was discovered after attempting to cross-compile the kernel library and running into the following error:

   0[100%] Linking CXX shared library libbitcoinkernel.dylib
   1/usr/bin/ld: unrecognised emulation mode: llvm
   2Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu i386pep i386pe
   3clang++: error: linker command failed with exit code 1 (use -v to see invocation)
   4gmake[3]: *** [src/kernel/CMakeFiles/bitcoinkernel.dir/build.make:1209: src/kernel/libbitcoinkernel.dylib] Error 1
   5gmake[2]: *** [CMakeFiles/Makefile2:1175: src/kernel/CMakeFiles/bitcoinkernel.dir/all] Error 2
   6gmake[1]: *** [CMakeFiles/Makefile2:1182: src/kernel/CMakeFiles/bitcoinkernel.dir/rule] Error 2
   7gmake: *** [Makefile:569: bitcoinkernel] Error 2
   

2. build: Set shared linker flags in toolchain file

   These are required when cross-compiling shared libraries such as the
   kernel library.

   a8e04704f9
3. 
   DrahtBot commented at 10:34 am on November 30, 2024: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/31395.

   Reviews

   See the guideline for information on the review process.

   Type	Reviewers
   ACK	hebasto, tdb3

   If your review is incorrectly listed, please react with 👎 to this comment and the bot will ignore it on the next update.

4. DrahtBot added the label Build system on Nov 30, 2024
5. hebasto approved
6. 
   hebasto commented at 9:25 am on December 1, 2024: member

   ACK a8e04704f930de168fdddbb1c040dd70fbbe8ff7, tested on Ubuntu 24.04:

   0$ make -C depends -j 16 HOST=arm64-apple-darwin NO_QT=1
   1$ cmake -B build --toolchain depends/arm64-apple-darwin/toolchain.cmake -DBUILD_SHARED_LIBS=ON -DBUILD_KERNEL_LIB=ON
   2$ cmake --build build -j 16 -t bitcoinkernel
   

   UPD. It seems to make sense to configure all CI jobs with -DBUILD_UTIL_CHAINSTATE=ON -DBUILD_KERNEL_LIB=ON -DBUILD_SHARED_LIBS=ON.

7. tdb3 approved
8. 
   tdb3 commented at 10:33 pm on December 1, 2024: contributor

   ACK a8e04704f930de168fdddbb1c040dd70fbbe8ff7

   On master, was able to reproduce a build error cross compiling for arm64-apple-darwin and x86_64-apple-darwin:

    0$ make -C depends HOST=arm64-apple-darwin -j11
    1$ cmake -B build -DBUILD_KERNEL_LIB=ON --toolchain depends/arm64-apple-darwin/toolchain.cmake
    2$ cmake --build build -j11
    3...
    4[ 38%] Linking CXX shared library libbitcoinkernel.dylib
    5/usr/bin/ld: unrecognised emulation mode: llvm
    6Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu i386pep i386pe
    7clang++: error: linker command failed with exit code 1 (use -v to see invocation)
    8gmake[2]: *** [src/kernel/CMakeFiles/bitcoinkernel.dir/build.make:1209: src/kernel/libbitcoinkernel.dylib] Error 1
    9gmake[1]: *** [CMakeFiles/Makefile2:1723: src/kernel/CMakeFiles/bitcoinkernel.dir/all] Error 2
   10gmake[1]: *** Waiting for unfinished jobs....
   11[ 38%] Linking CXX static library libbitcoin_common.a
   12[ 38%] Built target bitcoin_common
   13gmake: *** [Makefile:146: all] Error 2
   

    0$ make -C depends HOST=x86_64-apple-darwin -j11
    1$ cmake -B build -DBUILD_KERNEL_LIB=ON --toolchain depends/x86_64-apple-darwin/toolchain.cmake
    2$ cmake --build build -j11
    3...
    4[ 72%] Linking CXX shared library libbitcoinkernel.dylib
    5/usr/bin/ld: unrecognised emulation mode: llvm
    6Supported emulations: elf_x86_64 elf32_x86_64 elf_i386 elf_iamcu i386pep i386pe
    7clang++: error: linker command failed with exit code 1 (use -v to see invocation)
    8gmake[2]: *** [src/kernel/CMakeFiles/bitcoinkernel.dir/build.make:1211: src/kernel/libbitcoinkernel.dylib] Error 1
    9gmake[1]: *** [CMakeFiles/Makefile2:1838: src/kernel/CMakeFiles/bitcoinkernel.dir/all] Error 2
   10gmake: *** [Makefile:146: all] Error 2
   

   Was not able to reproduce the error building (on master) for riscv64-linux-gnu, arm-linux-gnueabihf, aarch64-linux-gnu, or x86_64-w64-mingw32.

   On the PR branch, was able to successfully cross compile for arm64-apple-darwin, x86_64-apple-darwin, riscv64-linux-gnu, arm-linux-gnueabihf, and aarch64-linux-gnu. (sanity checked with file build/src/kernel/libbitcoinkernel.{so/dylib} to see correct binary info).

   Ubuntu 24.04 with gcc 13.2.0 and clang 18.1.3.

9. fanquake merged this on Dec 2, 2024
10. fanquake closed this on Dec 2, 2024

    ---

11. 
    theuni commented at 6:14 pm on December 2, 2024: member

    Post-merge utACK a8e04704f930de168fdddbb1c040dd70fbbe8ff7

Contributors
TheCharlatan DrahtBot hebasto tdb3 theuni

Labels
Build system