LLVM openmp picks up math symbols despite not using them in any of its object files. $ cd /usr/ports/devel/openmp $ make install $ cd $(make -V WRKSRC) $ fgrep -lr scalbnl . ./runtime/src/libgomp.so ./runtime/src/libiomp5.so ./runtime/src/libomp.so ./runtime/exports/lin_32e/lib/libomp.so $ echo 'int main() { }' | cc ./runtime/src/libomp.so -xc - ./runtime/src/libomp.so: undefined reference to `scalbnl' ./runtime/src/libomp.so: undefined reference to `fmaxl' ./runtime/src/libomp.so: undefined reference to `logbl' ./runtime/src/libomp.so: undefined reference to `scalbnf' ./runtime/src/libomp.so: undefined reference to `logb' ./runtime/src/libomp.so: undefined reference to `logbf' ./runtime/src/libomp.so: undefined reference to `scalbn' cc: error: linker command failed with exit code 1 (use -v to see invocation) $ echo 'int main() { }' | cc -fopenmp -L/usr/local/lib -xc - /usr/local/lib/libomp.so: undefined reference to `scalbnl' /usr/local/lib/libomp.so: undefined reference to `fmaxl' /usr/local/lib/libomp.so: undefined reference to `logbl' /usr/local/lib/libomp.so: undefined reference to `scalbnf' /usr/local/lib/libomp.so: undefined reference to `logb' /usr/local/lib/libomp.so: undefined reference to `logbf' /usr/local/lib/libomp.so: undefined reference to `scalbn' cc: error: linker command failed with exit code 1 (use -v to see invocation)
Assigning to toolchain@ in order to help bisecting base change. It affects 11.0+ but not 10.3 or 9.3.
Created attachment 179304 [details] ports/devel/openmp/files/patch-link-libm.patch Sample patch for devel/openmp-3.9.0. The attached patch links libm. -Wl,--no-as-needed is necessary for forced linking. Before applying the patch) # ldd /usr/local/lib/libomp.so /usr/local/lib/libomp.so: libthr.so.3 => /lib/libthr.so.3 (0x801288000) libc.so.7 => /lib/libc.so.7 (0x800823000) After applying the patch) # ldd /usr/local/lib/libomp.so /usr/local/lib/libomp.so: libm.so.5 => /lib/libm.so.5 (0x801288000) libthr.so.3 => /lib/libthr.so.3 (0x8014b3000) libc.so.7 => /lib/libc.so.7 (0x800823000) $ echo 'int main() { }' | cc -fopenmp -L/usr/local/lib -xc - -v FreeBSD clang version 3.8.0 (tags/RELEASE_380/final 262564) (based on LLVM 3.8.0) Target: x86_64-unknown-freebsd11.0 Thread model: posix InstalledDir: /usr/bin "/usr/bin/cc" -cc1 -triple x86_64-unknown-freebsd11.0 -emit-obj -mrelax-all -disable-free -disable-llvm-verifier -main-file-name - -mrelocation-model static -mthread-model posix -mdisable-fp-elim -masm-verbose -mconstructor-aliases -munwind-tables -target-cpu x86-64 -v -dwarf-column-info -debugger-tuning=gdb -resource-dir /usr/bin/../lib/clang/3.8.0 -fdebug-compilation-dir /usr/home/nigoro -ferror-limit 19 -fmessage-length 172 -fopenmp -fobjc-runtime=gnustep -fdiagnostics-show-option -fcolor-diagnostics -o /tmp/--26d632.o -x c - clang -cc1 version 3.8.0 based upon LLVM 3.8.0 default target x86_64-unknown-freebsd11.0 #include "..." search starts here: #include <...> search starts here: /usr/bin/../lib/clang/3.8.0/include /usr/include End of search list. "/usr/bin/ld" --eh-frame-hdr -dynamic-linker /libexec/ld-elf.so.1 --hash-style=both --enable-new-dtags -o a.out /usr/lib/crt1.o /usr/lib/crti.o /usr/lib/crtbegin.o -L/usr/local/lib -L/usr/lib /tmp/--26d632.o -lomp -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/lib/crtend.o /usr/lib/crtn.o
To avoid maintenance burden it'd be nice if we fix base system regression before FreeBSD 11.1-RELEASE. devel/openmp isn't the only -lomp provider. $ fetch https://computing.llnl.gov/tutorials/openMP/samples/C/omp_hello.c $ pkg install llvm37 llvm38 llvm39 llvm40 llvm-devel $ find -s /usr/local -name libomp.so /usr/local/lib/libomp.so /usr/local/llvm-devel/lib/libomp.so /usr/local/llvm37/lib/libomp.so /usr/local/llvm38/lib/libomp.so /usr/local/llvm39/lib/libomp.so /usr/local/llvm40/lib/libomp.so $ clang37 -fopenmp omp_hello.c /usr/bin/ld: cannot find -lomp clang-3.7: error: linker command failed with exit code 1 (use -v to see invocation) $ clang37 -fopenmp omp_hello.c $(llvm-config37 --ldflags) /usr/local/llvm37/lib/libomp.so: undefined reference to `scalbnl' /usr/local/llvm37/lib/libomp.so: undefined reference to `fmaxl' /usr/local/llvm37/lib/libomp.so: undefined reference to `logbl' /usr/local/llvm37/lib/libomp.so: undefined reference to `scalbnf' /usr/local/llvm37/lib/libomp.so: undefined reference to `logb' /usr/local/llvm37/lib/libomp.so: undefined reference to `logbf' /usr/local/llvm37/lib/libomp.so: undefined reference to `scalbn' clang-3.7: error: linker command failed with exit code 1 (use -v to see invocation) $ clang38 -fopenmp omp_hello.c /usr/local/llvm38/lib/libomp.so: undefined reference to `scalbnl' /usr/local/llvm38/lib/libomp.so: undefined reference to `fmaxl' /usr/local/llvm38/lib/libomp.so: undefined reference to `logbl' /usr/local/llvm38/lib/libomp.so: undefined reference to `scalbnf' /usr/local/llvm38/lib/libomp.so: undefined reference to `logb' /usr/local/llvm38/lib/libomp.so: undefined reference to `logbf' /usr/local/llvm38/lib/libomp.so: undefined reference to `scalbn' clang-3.8: error: linker command failed with exit code 1 (use -v to see invocation) $ clang39 -fopenmp omp_hello.c /usr/local/llvm39/lib/libomp.so: undefined reference to `scalbnl' /usr/local/llvm39/lib/libomp.so: undefined reference to `fmaxl' /usr/local/llvm39/lib/libomp.so: undefined reference to `logbl' /usr/local/llvm39/lib/libomp.so: undefined reference to `scalbnf' /usr/local/llvm39/lib/libomp.so: undefined reference to `logb' /usr/local/llvm39/lib/libomp.so: undefined reference to `logbf' /usr/local/llvm39/lib/libomp.so: undefined reference to `scalbn' clang-3.9: error: linker command failed with exit code 1 (use -v to see invocation) $ clang40 -fopenmp omp_hello.c /usr/local/llvm40/lib/libomp.so: undefined reference to `scalbnl' /usr/local/llvm40/lib/libomp.so: undefined reference to `fmaxl' /usr/local/llvm40/lib/libomp.so: undefined reference to `logbl' /usr/local/llvm40/lib/libomp.so: undefined reference to `scalbnf' /usr/local/llvm40/lib/libomp.so: undefined reference to `logb' /usr/local/llvm40/lib/libomp.so: undefined reference to `logbf' /usr/local/llvm40/lib/libomp.so: undefined reference to `scalbn' clang-4.0: error: linker command failed with exit code 1 (use -v to see invocation) $ clang-devel -fopenmp omp_hello.c /usr/bin/ld: cannot find -lomp clang-5.0: error: linker command failed with exit code 1 (use -v to see invocation) $ clang-devel -fopenmp omp_hello.c $(llvm-config-devel --ldflags) /usr/local/llvm-devel/lib/libomp.so: undefined reference to `scalbnl' /usr/local/llvm-devel/lib/libomp.so: undefined reference to `fmaxl' /usr/local/llvm-devel/lib/libomp.so: undefined reference to `logbl' /usr/local/llvm-devel/lib/libomp.so: undefined reference to `scalbnf' /usr/local/llvm-devel/lib/libomp.so: undefined reference to `logb' /usr/local/llvm-devel/lib/libomp.so: undefined reference to `logbf' /usr/local/llvm-devel/lib/libomp.so: undefined reference to `scalbn' clang-5.0: error: linker command failed with exit code 1 (use -v to see invocation)
Comment on attachment 179304 [details] ports/devel/openmp/files/patch-link-libm.patch The workaround isn't really correct. FreeBSD versions before 11.0 don't really need -lm. $ clang40 -fopenmp omp_hello.c $ ldd a.out a.out: libomp.so => /usr/local/llvm40/lib/libomp.so (0x80081f000) libc.so.7 => /lib/libc.so.7 (0x800aa3000) libthr.so.3 => /lib/libthr.so.3 (0x800e50000)
(In reply to Jan Beich (mail not working) from comment #4) A library cannot 'pick up symbols without referencing them'. The presence of the the undefined references means that there are real references in the code. Note that existence of libm.so as a separate shared object from libc is a minor optimization. The libm services are mandated by the C standard, so the separate library is only a way to slighly reduce working set of the programs that do not need them. Linking it in is fine. If you are so intolerate to the presence of -lm in the dependency list even when symbols are not referenced, you can use '-Wl,--as-needed -lm -Wl,--no-as-needed' construct to only record DT_NEEDED fro libm.so when references actually exist.
(In reply to Konstantin Belousov from comment #5) > If you are so intolerate to the presence of -lm in the dependency > list even when symbols are not referenced, you can use > '-Wl,--as-needed -lm -Wl,--no-as-needed' construct to only record > DT_NEEDED fro libm.so when references actually exist. devel/openmp already adds -Wl,--as-needed and it doesn't work because the references come either from libgcc, crt or something similar.
LDFLAGS+=-Wl,--verbose diff shows: +(/usr/lib/libgcc.a)mulxc3.o +(/usr/lib/libgcc.a)mulsc3.o +(/usr/lib/libgcc.a)muldc3.o +(/usr/lib/libgcc.a)divxc3.o +(/usr/lib/libgcc.a)divsc3.o +(/usr/lib/libgcc.a)divdc3.o while nm kmp_atomic.cpp.o diff shows: - U _GLOBAL_OFFSET_TABLE_ + U __divdc3 + U __divsc3 + U __divxc3 + U __muldc3 + U __mulsc3 + U __mulxc3 but using older libgcc.a won't help: $ nm -A /poudriere/jails/103amd64/usr/lib/libgcc.a | fgrep scalbnl /poudriere/jails/103amd64/usr/lib/libgcc.a:divxc3.o: U scalbnl $ nm -A /poudriere/jails/110amd64/usr/lib/libgcc.a | fgrep scalbnl /poudriere/jails/110amd64/usr/lib/libgcc.a:divxc3.o: U scalbnl /poudriere/jails/110amd64/usr/lib/libgcc.a:divtc3.o: U scalbnl
(In reply to Jan Beich (mail not working) from comment #7) Which means that libm is really needed.
Maybe but cc -E doesn't show any calls to __divdc3 et al.
(In reply to Jan Beich (mail not working) from comment #9) Why it should ? The symbols like __divdc3 are referenced by a compiler-generated code, for instance the __divdc3 definition is complex double __divdc3 (double a, double b, double c, double d) with the semantic of return ((a + i * b) / (c + i * d)), where i is imaginary one. The source code should contain complex division operation, not __divdc3 call, to get the reference.
Because if compiler emits undefined references the linker cannot be expected to know when -lm is required. Looking at contrib/llvm/tools/clang/lib/Driver/Tools.cpp there are already cases when -lm is passed together with --no-as-needed. Maybe something like https://reviews.llvm.org/D5698 added one more case.
2017Q2 is around the corner, so I've landed before upstream review. ;\ https://svnweb.freebsd.org/changeset/ports/437204
A commit references this bug: Author: jbeich Date: Wed Mar 29 14:43:30 UTC 2017 New revision: 437204 URL: https://svnweb.freebsd.org/changeset/ports/437204 Log: devel/openmp: link libomp.so against -lm for clang 3.6+ PR: 214258 Submitted by: Yuta Satoh <nigoro.dev@gmail.com> Approved by: portmgr blanket Changes: head/devel/llvm-devel/Makefile head/devel/llvm-devel/files/openmp-patch-bug32279 head/devel/llvm37/Makefile head/devel/llvm37/files/openmp-patch-bug32279 head/devel/llvm38/Makefile head/devel/llvm38/files/openmp-patch-bug32279 head/devel/llvm39/Makefile head/devel/llvm39/files/openmp-patch-bug32279 head/devel/llvm40/Makefile head/devel/llvm40/files/openmp-patch-bug32279 head/devel/openmp/Makefile head/devel/openmp/files/patch-bug32279