Failure during linking when building Libretro Switch core

[aitorciki]

Platform / OS / Hardware: Nintendo Switch
Github hash: bc3c1ab
Hardware: building on AMD64 Windows + MSYS2 or Ubuntu

Trying to build a libretro core for Nintendo Switch following these steps fails during linking of the RetroArch binary with the core. Flycast core builds correctly, RetroArch builds correctly, but linking fails due to undefined references (notably to CMakeRC resources):

$ make -f Makefile.libnx
linking retroarch_switch.elf
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: /opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: DWARF error: can't find .debug_ranges section.
libretro_libnx.a(printer.o): in function `printer::BitmapWriter::BitmapWriter(int)':
printer.cpp:(.text._ZN7printer12BitmapWriterC2Ei[_ZN7printer12BitmapWriterC5Ei]+0x64): undefined reference to `cmrc::flycast::get_filesystem()'
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: /opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: DWARF error: can't find .debug_ranges section.
libretro_libnx.a(reios.o): in function `reios_reset(unsigned char*)':
reios.cpp:(.text._Z11reios_resetPh+0x9c): undefined reference to `cmrc::flycast::get_filesystem()'
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: /opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: DWARF error: can't find .debug_ranges section.
libretro_libnx.a(reios_elf.o): in function `reios_loadElf(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
reios_elf.cpp:(.text._Z13reios_loadElfRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0xa4): undefined reference to `elf_newFile'
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: reios_elf.cpp:(.text._Z13reios_loadElfRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0xe0): undefined reference to `elf_checkFile'
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: reios_elf.cpp:(.text._Z13reios_loadElfRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x104): undefined reference to `elf_getNumProgramHeaders'
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: reios_elf.cpp:(.text._Z13reios_loadElfRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x11c): undefined reference to `elf_getProgramHeaderVaddr'
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: reios_elf.cpp:(.text._Z13reios_loadElfRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x12c): undefined reference to `elf_getProgramHeaderFileSize'
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: reios_elf.cpp:(.text._Z13reios_loadElfRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x140): undefined reference to `elf_getProgramHeaderOffset'
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: reios_elf.cpp:(.text._Z13reios_loadElfRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE+0x174): undefined reference to `elf_getProgramHeaderMemorySize'
/opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: /opt/devkitpro/devkitA64/bin/../lib/gcc/aarch64-none-elf/13.1.0/../../../../aarch64-none-elf/bin/ld: DWARF error: can't find .debug_ranges section.
libretro_libnx.a(nvmem.o): in function `nvmem::loadFlashResource(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, unsigned long&)':
nvmem.cpp:(.text._ZN5nvmemL17loadFlashResourceERKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEERm+0x20): undefined reference to `cmrc::flycast::get_filesystem()'
collect2: error: ld returned 1 exit status
make: *** [/opt/devkitpro/libnx/switch_rules:81: retroarch_switch.elf] Error 1

Steps to reproduce:

• Flycast built using CMake commands used in GitHub workflows:
  • $DEVKITPRO/portlibs/switch/bin/aarch64-none-elf-cmake -B build -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=artifact -G Ninja -DLIBRETRO=ON (CMakeLists.txt slightly modified to replace expected *.obj files with the generated *.o files in last build step)
  • cmake --build build --config Release --target install
• Resulting flycast_libretro_libnx.a artifact copied to retroarch directory as libretro_libnx.a
• RetroArch built with make -f Makefile.libnx

[flyinghead]

Unfortunately the retroarch switch build isn't being maintained so it's not surprising that it's failing.
I believe you need an additional step to include all object files from dependent libraries (libelf.a, libflycast-resources.a) into the libretro_libnx.a library.

[flyinghead]

oh actually it's done in CMakeLists.txt:

add_custom_target(combined ALL
	COMMAND ${CMAKE_AR} -x $<TARGET_FILE:xxHash::xxhash>
	COMMAND ${CMAKE_AR} -x $<TARGET_FILE:chdr-static>
	COMMAND ${CMAKE_AR} -x $<TARGET_FILE:zip>
	COMMAND ${CMAKE_AR} -rs flycast_libretro_libnx.a *.obj
	COMMAND rm *.obj

Adding the two previously mentioned libraries to the list should fix the issue.

[flyinghead]

as in:

add_custom_target(combined ALL
	COMMAND ${CMAKE_AR} -x $<TARGET_FILE:xxHash::xxhash>
	COMMAND ${CMAKE_AR} -x $<TARGET_FILE:chdr-static>
	COMMAND ${CMAKE_AR} -x $<TARGET_FILE:zip>
	COMMAND ${CMAKE_AR} -x $<TARGET_FILE:elf>
	COMMAND ${CMAKE_AR} -x $<TARGET_FILE:flycast::res>
	COMMAND ${CMAKE_AR} -rs flycast_libretro_libnx.a *.obj

[aitorciki]

Hey, thanks for the guidance (I'm a total newby to CMake).

I added the dependencies as proposed (renaming *.obj to *.o, probably caused by my using a newer devkitpro version?):

add_custom_target(combined ALL
        COMMAND ${CMAKE_AR} -x $<TARGET_FILE:xxHash::xxhash>
        COMMAND ${CMAKE_AR} -x $<TARGET_FILE:chdr-static>
        COMMAND ${CMAKE_AR} -x $<TARGET_FILE:zip>
        COMMAND ${CMAKE_AR} -x $<TARGET_FILE:elf>
        COMMAND ${CMAKE_AR} -x $<TARGET_FILE:flycast::res>
        COMMAND ${CMAKE_AR} -rs flycast_libretro_libnx.a *.o
        COMMAND rm *.o
        WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_ARCHIVE_OUTPUT_DIRECTORY}
        DEPENDS xxHash::xxhash chdr-static zip elf flycast::res ${PROJECT_NAME})

The up-to-date core now builds and runs nicely!

Probably worth updating for folks who want an up-to-date Switch core, happy to make a PR if needed (still curious by the *.obj vs *.o situation though).

[flyinghead]

I'll fix CMakeLists.txt now that you've confirmed that it's building fine.

The *.obj vs. *.o issue is due to a change in the devkitpro environment. Flycast is being built with an old devkitpro version because new ones have performance issues. Unfortunately I can't test since I don't have a switch so I have to rely on user reports.

[flyinghead]

fixed by the commit above