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gollvm: -fPIC is not supported, if using ld or lld, with Clang++ #41527

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advancedwebdeveloper opened this issue Sep 21, 2020 · 4 comments
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@advancedwebdeveloper
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@advancedwebdeveloper advancedwebdeveloper commented Sep 21, 2020

I was figuring out linker's options.
So if I am properly dealing with CMake's flags

cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_USE_LINKER=ld -DGOLLVM_DEFAULT_LINKER=ld -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_FLAGS=' -stdlib=libc++ -fuse-ld=ld ' -DLLVM_TARGETS_TO_BUILD=X86 -G Ninja ../llvm-project/llvm

should be what I tried.
And lld is invoked via

cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_USE_LINKER=lld -DGOLLVM_DEFAULT_LINKER=lld -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_FLAGS=' -stdlib=libc++ -fuse-ld=lld ' -DLLVM_TARGETS_TO_BUILD=X86 -G Ninja ../llvm-project/llvm
.
One of there option lad to this:

-- The C compiler identification is Clang 11.0.0
-- The CXX compiler identification is Clang 11.0.0
-- The ASM compiler identification is Clang
-- Found assembler: /usr/bin/clang
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/clang - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Performing Test LLVM_LIBSTDCXX_MIN
-- Performing Test LLVM_LIBSTDCXX_MIN - Success
-- Performing Test LLVM_LIBSTDCXX_SOFT_ERROR
-- Performing Test LLVM_LIBSTDCXX_SOFT_ERROR - Success
-- Looking for dlfcn.h
-- Looking for dlfcn.h - found
-- Looking for errno.h
-- Looking for errno.h - found
-- Looking for fcntl.h
-- Looking for fcntl.h - found
-- Looking for link.h
-- Looking for link.h - found
-- Looking for malloc/malloc.h
-- Looking for malloc/malloc.h - not found
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Looking for signal.h
-- Looking for signal.h - found
-- Looking for sys/ioctl.h
-- Looking for sys/ioctl.h - found
-- Looking for sys/mman.h
-- Looking for sys/mman.h - found
-- Looking for sys/param.h
-- Looking for sys/param.h - found
-- Looking for sys/resource.h
-- Looking for sys/resource.h - found
-- Looking for sys/stat.h
-- Looking for sys/stat.h - found
-- Looking for sys/time.h
-- Looking for sys/time.h - found
-- Looking for sys/types.h
-- Looking for sys/types.h - found
-- Looking for sysexits.h
-- Looking for sysexits.h - found
-- Looking for termios.h
-- Looking for termios.h - found
-- Looking for unistd.h
-- Looking for unistd.h - found
-- Looking for valgrind/valgrind.h
-- Looking for valgrind/valgrind.h - found
-- Looking for fenv.h
-- Looking for fenv.h - found
-- Looking for FE_ALL_EXCEPT
-- Looking for FE_ALL_EXCEPT - found
-- Looking for FE_INEXACT
-- Looking for FE_INEXACT - found
-- Looking for mach/mach.h
-- Looking for mach/mach.h - not found
-- Looking for histedit.h
-- Looking for histedit.h - not found
-- Looking for CrashReporterClient.h
-- Looking for CrashReporterClient.h - not found
-- Looking for linux/magic.h
-- Looking for linux/magic.h - found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Looking for pthread_getspecific in pthread
-- Looking for pthread_getspecific in pthread - found
-- Looking for pthread_rwlock_init in pthread
-- Looking for pthread_rwlock_init in pthread - found
-- Looking for pthread_mutex_lock in pthread
-- Looking for pthread_mutex_lock in pthread - found
-- Looking for dlopen in dl
-- Looking for dlopen in dl - found
-- Looking for clock_gettime in rt
-- Looking for clock_gettime in rt - found
-- Looking for pfm_initialize in pfm
-- Looking for pfm_initialize in pfm - not found
-- Looking for pthread.h
-- Looking for pthread.h - found
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD
-- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
-- Looking for pthread_create in pthreads
-- Looking for pthread_create in pthreads - not found
-- Looking for pthread_create in pthread
-- Looking for pthread_create in pthread - found
-- Found Threads: TRUE
-- Found ZLIB: /usr/lib/x86_64-linux-gnu/libz.so (found version "1.2.11")
-- Looking for compress2
-- Looking for compress2 - found
-- Could NOT find LibXml2 (missing: LIBXML2_LIBRARY LIBXML2_INCLUDE_DIR)
-- Looking for xar_open in xar
-- Looking for xar_open in xar - not found
-- Looking for arc4random
-- Looking for arc4random - not found
-- Looking for backtrace
-- Looking for backtrace - found
-- backtrace facility detected in default set of libraries
-- Found Backtrace: /usr/include
-- Performing Test C_SUPPORTS_WERROR_UNGUARDED_AVAILABILITY_NEW
-- Performing Test C_SUPPORTS_WERROR_UNGUARDED_AVAILABILITY_NEW - Success
-- Looking for _Unwind_Backtrace
-- Looking for _Unwind_Backtrace - found
-- Looking for getpagesize
-- Looking for getpagesize - found
-- Looking for sysconf
-- Looking for sysconf - found
-- Looking for getrusage
-- Looking for getrusage - found
-- Looking for setrlimit
-- Looking for setrlimit - found
-- Looking for isatty
-- Looking for isatty - found
-- Looking for futimens
-- Looking for futimens - found
-- Looking for futimes
-- Looking for futimes - found
-- Looking for posix_fallocate
-- Looking for posix_fallocate - found
-- Looking for sigaltstack
-- Looking for sigaltstack - found
-- Looking for lseek64
-- Looking for lseek64 - found
-- Looking for mallctl
-- Looking for mallctl - not found
-- Looking for mallinfo
-- Looking for mallinfo - found
-- Looking for malloc_zone_statistics
-- Looking for malloc_zone_statistics - not found
-- Looking for getrlimit
-- Looking for getrlimit - found
-- Looking for posix_spawn
-- Looking for posix_spawn - found
-- Looking for pread
-- Looking for pread - found
-- Looking for sbrk
-- Looking for sbrk - found
-- Looking for strerror
-- Looking for strerror - found
-- Looking for strerror_r
-- Looking for strerror_r - found
-- Looking for strerror_s
-- Looking for strerror_s - not found
-- Looking for setenv
-- Looking for setenv - found
-- Looking for dlopen
-- Looking for dlopen - found
-- Looking for dladdr
-- Looking for dladdr - not found
-- Performing Test HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC
-- Performing Test HAVE_STRUCT_STAT_ST_MTIMESPEC_TV_NSEC - Failed
-- Performing Test HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC
-- Performing Test HAVE_STRUCT_STAT_ST_MTIM_TV_NSEC - Success
-- Looking for GLIBC
-- Looking for GLIBC - found
-- Looking for pthread_getname_np
-- Looking for pthread_getname_np - found
-- Looking for pthread_setname_np
-- Looking for pthread_setname_np - found
-- Performing Test HAVE_STD_IS_TRIVIALLY_COPYABLE
-- Performing Test HAVE_STD_IS_TRIVIALLY_COPYABLE - Success
-- Performing Test HAVE_CXX_ATOMICS_WITHOUT_LIB
-- Performing Test HAVE_CXX_ATOMICS_WITHOUT_LIB - Success
-- Performing Test HAVE_CXX_ATOMICS64_WITHOUT_LIB
-- Performing Test HAVE_CXX_ATOMICS64_WITHOUT_LIB - Success
-- Performing Test LLVM_HAS_ATOMICS
-- Performing Test LLVM_HAS_ATOMICS - Success
-- Performing Test SUPPORTS_VARIADIC_MACROS_FLAG
-- Performing Test SUPPORTS_VARIADIC_MACROS_FLAG - Success
-- Performing Test SUPPORTS_GNU_ZERO_VARIADIC_MACRO_ARGUMENTS_FLAG
-- Performing Test SUPPORTS_GNU_ZERO_VARIADIC_MACRO_ARGUMENTS_FLAG - Success
-- Native target architecture is X86
-- Threads enabled.
-- Doxygen disabled.
-- Go bindings disabled.
-- Ninja version: 1.10.0.git.kitware.jobserver-1
-- Could NOT find OCaml (missing: OCAMLFIND OCAML_VERSION OCAML_STDLIB_PATH)
-- Could NOT find OCaml (missing: OCAMLFIND OCAML_VERSION OCAML_STDLIB_PATH)
-- OCaml bindings disabled.
-- Could NOT find Python module pygments
-- Could NOT find Python module pygments.lexers.c_cpp
-- Could NOT find Python module yaml
-- LLVM host triple: x86_64-unknown-linux-gnu
-- LLVM default target triple: x86_64-unknown-linux-gnu
-- Performing Test CXX_SUPPORTS_CUSTOM_LINKER
-- Performing Test CXX_SUPPORTS_CUSTOM_LINKER - Success
-- Performing Test C_SUPPORTS_FPIC
-- Performing Test C_SUPPORTS_FPIC - Success
-- Performing Test CXX_SUPPORTS_FPIC
-- Performing Test CXX_SUPPORTS_FPIC - Failed
> CMake Warning at cmake/modules/HandleLLVMOptions.cmake:261 (message):
-fPIC is not supported.

Call Stack (most recent call first):
cmake/modules/HandleLLVMOptions.cmake:297 (add_flag_or_print_warning)
CMakeLists.txt:697 (include)

-- Performing Test SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG
-- Performing Test SUPPORTS_FVISIBILITY_INLINES_HIDDEN_FLAG - Success
-- Performing Test C_SUPPORTS_WERROR_DATE_TIME
-- Performing Test C_SUPPORTS_WERROR_DATE_TIME - Success
-- Performing Test CXX_SUPPORTS_WERROR_DATE_TIME
-- Performing Test CXX_SUPPORTS_WERROR_DATE_TIME - Failed
-- Performing Test CXX_SUPPORTS_WERROR_UNGUARDED_AVAILABILITY_NEW
-- Performing Test CXX_SUPPORTS_WERROR_UNGUARDED_AVAILABILITY_NEW - Failed
-- Performing Test CXX_SUPPORTS_MISSING_FIELD_INITIALIZERS_FLAG
-- Performing Test CXX_SUPPORTS_MISSING_FIELD_INITIALIZERS_FLAG - Success
-- Performing Test C_SUPPORTS_IMPLICIT_FALLTHROUGH_FLAG
-- Performing Test C_SUPPORTS_IMPLICIT_FALLTHROUGH_FLAG - Success
-- Performing Test CXX_SUPPORTS_IMPLICIT_FALLTHROUGH_FLAG
-- Performing Test CXX_SUPPORTS_IMPLICIT_FALLTHROUGH_FLAG - Failed
-- Performing Test C_SUPPORTS_COVERED_SWITCH_DEFAULT_FLAG
-- Performing Test C_SUPPORTS_COVERED_SWITCH_DEFAULT_FLAG - Success
-- Performing Test CXX_SUPPORTS_COVERED_SWITCH_DEFAULT_FLAG
-- Performing Test CXX_SUPPORTS_COVERED_SWITCH_DEFAULT_FLAG - Failed
-- Performing Test CXX_SUPPORTS_CLASS_MEMACCESS_FLAG
-- Performing Test CXX_SUPPORTS_CLASS_MEMACCESS_FLAG - Failed
-- Performing Test CXX_SUPPORTS_NOEXCEPT_TYPE_FLAG
-- Performing Test CXX_SUPPORTS_NOEXCEPT_TYPE_FLAG - Success
-- Performing Test CXX_WONT_WARN_ON_FINAL_NONVIRTUALDTOR
-- Performing Test CXX_WONT_WARN_ON_FINAL_NONVIRTUALDTOR - Success
-- Performing Test C_SUPPORTS_DELETE_NON_VIRTUAL_DTOR_FLAG
-- Performing Test C_SUPPORTS_DELETE_NON_VIRTUAL_DTOR_FLAG - Success
-- Performing Test CXX_SUPPORTS_DELETE_NON_VIRTUAL_DTOR_FLAG
-- Performing Test CXX_SUPPORTS_DELETE_NON_VIRTUAL_DTOR_FLAG - Failed
-- Performing Test CXX_SUPPORTS_SUGGEST_OVERRIDE_FLAG
-- Performing Test CXX_SUPPORTS_SUGGEST_OVERRIDE_FLAG - Success
-- Performing Test CXX_WSUGGEST_OVERRIDE_ALLOWS_ONLY_FINAL
-- Performing Test CXX_WSUGGEST_OVERRIDE_ALLOWS_ONLY_FINAL - Success
-- Performing Test C_WCOMMENT_ALLOWS_LINE_WRAP
-- Performing Test C_WCOMMENT_ALLOWS_LINE_WRAP - Success
-- Performing Test C_SUPPORTS_STRING_CONVERSION_FLAG
-- Performing Test C_SUPPORTS_STRING_CONVERSION_FLAG - Success
-- Performing Test CXX_SUPPORTS_STRING_CONVERSION_FLAG
-- Performing Test CXX_SUPPORTS_STRING_CONVERSION_FLAG - Failed
-- Performing Test LINKER_SUPPORTS_COLOR_DIAGNOSTICS
-- Performing Test LINKER_SUPPORTS_COLOR_DIAGNOSTICS - Failed
-- Performing Test C_SUPPORTS_FNO_FUNCTION_SECTIONS
-- Performing Test C_SUPPORTS_FNO_FUNCTION_SECTIONS - Success
-- Performing Test C_SUPPORTS_FFUNCTION_SECTIONS
-- Performing Test C_SUPPORTS_FFUNCTION_SECTIONS - Success
-- Performing Test CXX_SUPPORTS_FFUNCTION_SECTIONS
-- Performing Test CXX_SUPPORTS_FFUNCTION_SECTIONS - Failed
-- Performing Test C_SUPPORTS_FDATA_SECTIONS
-- Performing Test C_SUPPORTS_FDATA_SECTIONS - Success
-- Performing Test CXX_SUPPORTS_FDATA_SECTIONS
-- Performing Test CXX_SUPPORTS_FDATA_SECTIONS - Failed
-- Looking for os_signpost_interval_begin
-- Looking for os_signpost_interval_begin - not found
-- Found Python3: /usr/bin/python3.8 (found version "3.8.2") found components: Interpreter
-- Constructing LLVMBuild project information
-- Linker detection: GNU ld
-- Found Git: /usr/bin/git (found version "2.25.1")
-- Targeting X86
-- default linker set to "ld"
-- Performing Test C_SUPPORTS_CF_PROTECTION_BRANCH
-- Performing Test C_SUPPORTS_CF_PROTECTION_BRANCH - Success
-- Performing Test SPLIT_STACK_FUNCTIONAL
-- Performing Test SPLIT_STACK_FUNCTIONAL - Success
-- starting libgo configuration.
-- Performing Test HAVE_ATOMIC_FUNCTIONS
-- Performing Test HAVE_ATOMIC_FUNCTIONS - Success
-- Looking for clock_gettime
-- Looking for clock_gettime - found
-- Looking for strnlen
-- Looking for strnlen - found
-- Looking for dl_iterate_phdr
-- Looking for dl_iterate_phdr - found
-- Looking for fcntl
-- Looking for fcntl - found
-- Looking for getexecname
-- Looking for getexecname - not found
-- Looking for lstat
-- Looking for lstat - found
-- Looking for readlink
-- Looking for readlink - found
-- Looking for mmap
-- Looking for mmap - found
-- Looking for accept4
-- Looking for accept4 - found
-- Looking for dup3
-- Looking for dup3 - found
-- Looking for epoll_create1
-- Looking for epoll_create1 - found
-- Looking for faccessat
-- Looking for faccessat - found
-- Looking for fallocate
-- Looking for fallocate - found
-- Looking for fchmodat
-- Looking for fchmodat - found
-- Looking for fchownat
-- Looking for fchownat - found
-- Looking for futimesat
-- Looking for futimesat - found
-- Looking for inotify_add_watch
-- Looking for inotify_add_watch - found
-- Looking for inotify_init
-- Looking for inotify_init - found
-- Looking for inotify_init1
-- Looking for inotify_init1 - found
-- Looking for inotify_rm_watch
-- Looking for inotify_rm_watch - found
-- Looking for listxattr
-- Looking for listxattr - found
-- Looking for mincore
-- Looking for mincore - found
-- Looking for mkdirat
-- Looking for mkdirat - found
-- Looking for openat
-- Looking for openat - found
-- Looking for removexattr
-- Looking for removexattr - found
-- Looking for renameat
-- Looking for renameat - found
-- Looking for setxattr
-- Looking for setxattr - found
-- Looking for splice
-- Looking for splice - found
-- Looking for sync_file_range
-- Looking for sync_file_range - found
-- Looking for syscall
-- Looking for syscall - found
-- Looking for tee
-- Looking for tee - found
-- Looking for unlinkat
-- Looking for unlinkat - found
-- Looking for unsetenv
-- Looking for unsetenv - found
-- Looking for unshare
-- Looking for unshare - found
-- Looking for utimensat
-- Looking for utimensat - found
-- Looking for wait4
-- Looking for wait4 - found
-- Looking for open64
-- Looking for open64 - found
-- Looking for mknodat
-- Looking for mknodat - found
-- Looking for pipe2
-- Looking for pipe2 - found
-- Looking for memmem
-- Looking for memmem - found
-- Looking for inttypes.h
-- Looking for inttypes.h - found
-- Looking for linux/ether.h
-- Looking for linux/ether.h - not found
-- Looking for linux/filter.h
-- Looking for linux/filter.h - found
-- Looking for linux/fs.h
-- Looking for linux/fs.h - found
-- Looking for linux/if_addr.h
-- Looking for linux/if_addr.h - found
-- Looking for linux/if_ether.h
-- Looking for linux/if_ether.h - found
-- Looking for linux/if_tun.h
-- Looking for linux/if_tun.h - found
-- Looking for linux/netlink.h
-- Looking for linux/netlink.h - found
-- Looking for linux/ptrace.h
-- Looking for linux/ptrace.h - found
-- Looking for linux/reboot.h
-- Looking for linux/reboot.h - found
-- Looking for linux/rtnetlink.h
-- Looking for linux/rtnetlink.h - found
-- Looking for memory.h
-- Looking for memory.h - found
-- Looking for net/if.h
-- Looking for net/if.h - found
-- Looking for net/if_arp.h
-- Looking for net/if_arp.h - found
-- Looking for net/route.h
-- Looking for net/route.h - found
-- Looking for netinet/icmp6.h
-- Looking for netinet/icmp6.h - found
-- Looking for netinet/if_ether.h
-- Looking for netinet/if_ether.h - found
-- Looking for netinet/in_systm.h
-- Looking for netinet/in_systm.h - found
-- Looking for netinet/ip.h
-- Looking for netinet/ip.h - found
-- Looking for netinet/ip_mroute.h
-- Looking for netinet/ip_mroute.h - not found
-- Looking for netpacket/packet.h
-- Looking for netpacket/packet.h - found
-- Looking for port.h
-- Looking for port.h - not found
-- Looking for sched.h
-- Looking for sched.h - found
-- Looking for semaphore.h
-- Looking for semaphore.h - found
-- Looking for stdint.h
-- Looking for stdint.h - found
-- Looking for stdlib.h
-- Looking for stdlib.h - found
-- Looking for strings.h
-- Looking for strings.h - found
-- Looking for sys/epoll.h
-- Looking for sys/epoll.h - found
-- Looking for sys/file.h
-- Looking for sys/file.h - found
-- Looking for sys/inotify.h
-- Looking for sys/inotify.h - found
-- Looking for sys/mount.h
-- Looking for sys/mount.h - found
-- Looking for sys/prctl.h
-- Looking for sys/prctl.h - found
-- Looking for sys/ptrace.h
-- Looking for sys/ptrace.h - found
-- Looking for sys/select.h
-- Looking for sys/select.h - found
-- Looking for sys/statfs.h
-- Looking for sys/statfs.h - found
-- Looking for sys/syscall.h
-- Looking for sys/syscall.h - found
-- Looking for sys/sysinfo.h
-- Looking for sys/sysinfo.h - found
-- Looking for sys/timex.h
-- Looking for sys/timex.h - found
-- Looking for sys/user.h
-- Looking for sys/user.h - found
-- Looking for sys/utsname.h
-- Looking for sys/utsname.h - found
-- Looking for sys/vfs.h
-- Looking for sys/vfs.h - found
-- Looking for syscall.h
-- Looking for syscall.h - found
-- Looking for utime.h
-- Looking for utime.h - found
-- Looking for compress in z
-- Looking for compress in z - found
-- Looking for stddef.h
-- Looking for stddef.h - found
-- Check size of double
-- Check size of double - done
-- Check size of long double
-- Check size of long double - done
-- Check size of long double
-- Check size of long double - done
-- Check size of void*
-- Check size of void* - done
-- Looking for alloca.h
-- Looking for alloca.h - found
-- Looking for alloca
-- Looking for alloca - not found
-- Looking for memcpy
-- Looking for memcpy - found
-- Performing Test HAVE_SYNC_BOOL_COMPARE_AND_SWAP_4
-- Performing Test HAVE_SYNC_BOOL_COMPARE_AND_SWAP_4 - Success
-- Performing Test HAVE_SYNC_BOOL_COMPARE_AND_SWAP_8
-- Performing Test HAVE_SYNC_BOOL_COMPARE_AND_SWAP_8 - Success
-- Performing Test HAVE_AS_X86_AES
-- Performing Test HAVE_AS_X86_AES - Success
-- Libgo: creating stdlib package targets
-- Libgo: generating check targets
-- libgo configuration complete.
-- starting gotools configuration.
-- gotools: generating check targets
-- gotools configuration complete.
-- Registering Bye as a pass plugin (static build: OFF)
-- Failed to find LLVM FileCheck
-- Version: 0.0.0
-- Performing Test HAVE_CXX_FLAG_STD_CXX11
-- Performing Test HAVE_CXX_FLAG_STD_CXX11 - Success
-- Performing Test HAVE_CXX_FLAG_WALL
-- Performing Test HAVE_CXX_FLAG_WALL - Success
-- Performing Test HAVE_CXX_FLAG_WEXTRA
-- Performing Test HAVE_CXX_FLAG_WEXTRA - Success
-- Performing Test HAVE_CXX_FLAG_WSHADOW
-- Performing Test HAVE_CXX_FLAG_WSHADOW - Success
-- Performing Test HAVE_CXX_FLAG_PEDANTIC
-- Performing Test HAVE_CXX_FLAG_PEDANTIC - Success
-- Performing Test HAVE_CXX_FLAG_PEDANTIC_ERRORS
-- Performing Test HAVE_CXX_FLAG_PEDANTIC_ERRORS - Success
-- Performing Test HAVE_CXX_FLAG_WSHORTEN_64_TO_32
-- Performing Test HAVE_CXX_FLAG_WSHORTEN_64_TO_32 - Success
-- Performing Test HAVE_CXX_FLAG_WFLOAT_EQUAL
-- Performing Test HAVE_CXX_FLAG_WFLOAT_EQUAL - Success
-- Performing Test HAVE_CXX_FLAG_FSTRICT_ALIASING
-- Performing Test HAVE_CXX_FLAG_FSTRICT_ALIASING - Success
-- Performing Test HAVE_CXX_FLAG_FNO_EXCEPTIONS
-- Performing Test HAVE_CXX_FLAG_FNO_EXCEPTIONS - Success
-- Performing Test HAVE_CXX_FLAG_WNO_SUGGEST_OVERRIDE
-- Performing Test HAVE_CXX_FLAG_WNO_SUGGEST_OVERRIDE - Success
-- Performing Test HAVE_CXX_FLAG_WSTRICT_ALIASING
-- Performing Test HAVE_CXX_FLAG_WSTRICT_ALIASING - Success
-- Performing Test HAVE_CXX_FLAG_WD654
-- Performing Test HAVE_CXX_FLAG_WD654 - Failed
-- Performing Test HAVE_CXX_FLAG_WTHREAD_SAFETY
-- Performing Test HAVE_CXX_FLAG_WTHREAD_SAFETY - Success
-- Performing Test HAVE_THREAD_SAFETY_ATTRIBUTES
-- Performing Test HAVE_THREAD_SAFETY_ATTRIBUTES
-- Performing Test HAVE_THREAD_SAFETY_ATTRIBUTES -- failed to compile
-- Performing Test HAVE_CXX_FLAG_COVERAGE
-- Performing Test HAVE_CXX_FLAG_COVERAGE - Success
-- Performing Test HAVE_GNU_POSIX_REGEX
-- Performing Test HAVE_GNU_POSIX_REGEX
-- Performing Test HAVE_GNU_POSIX_REGEX -- failed to compile
-- Performing Test HAVE_POSIX_REGEX
-- Performing Test HAVE_POSIX_REGEX
-- Performing Test HAVE_POSIX_REGEX -- success
-- Performing Test HAVE_STEADY_CLOCK
-- Performing Test HAVE_STEADY_CLOCK
-- Performing Test HAVE_STEADY_CLOCK -- success
-- Configuring done
-- Generating done
-- Build files have been written to: /home/oceanfish81/workarea/gollvm_compile_attempt

If I do like this:

cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_FLAGS=' -stdlib=libc++ ' -DLLVM_TARGETS_TO_BUILD=X86 -G Ninja ../llvm-project/llvm
CMake reports that "gold" is choosen, as a linker.
What is confusing is that I do not clearly where and how specific linker is chosen to link gollvm and which linker would be estimated for invoking by llvm-goc (after the installation).

There is no clear/current summary on -fPIC flag support, in some practical manner. I am proposing that it should be documented.

Ivan

@ianlancetaylor ianlancetaylor changed the title [gollvm] -fPIC is not supported, if using ld or lld, with Clang++ gollvm: -fPIC is not supported, if using ld or lld, with Clang++ Sep 21, 2020
@ianlancetaylor ianlancetaylor added this to the gollvm milestone Sep 21, 2020
@ianlancetaylor
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@ianlancetaylor ianlancetaylor commented Sep 21, 2020

@thanm
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@thanm thanm commented Sep 21, 2020

For some reason it looks as though some of the cmake config checks that LLVM runs (this is outside of the gollvm cmake rules) are using -Werror (but only for C++ compiles, not for C compiles). So what's happening is that the cmake rules run "clang++ -c foo.cpp -fuse-ld=..." and clang warns because the linker option is not used ... and then the warning is turned into an error. I guess I would tack on "-Qunused-arguments" in this situation in addition to "-fuse-ld=xxx".

Also, not sure what the intended effect of "-fuse-ld=ld" is. The argument of this option should be one of {bfd,gold,ldd}.

@advancedwebdeveloper
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@advancedwebdeveloper advancedwebdeveloper commented Sep 22, 2020

@lattner , @topperc, @RKSimon, @arsenm, @echristo , @tobiasgrosser , @EricWF , @ppc : could you clarify an actual summary, for specific linkers, without CMake's auto-detection?
I guess that requires updating CMake's configs, to allow providing gollvm specific warnings/constraints, during the build process.

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