Description
NOTE -- please read
If you see lines starting with ld: warning but not other outputs, they are just warnings, not errors. You should still get a working binary, if there is no other output. Please only report if you see a link error, or a broken binary, or a warning that is not mentioned in the "warnings" section below. Thanks.
See #61229 (comment) for more notes about malformed LC_DYSYMTAB warning. Thanks.
In Xcode 15 beta it comes with Apple's new linker, ld-prime. As of beta 3 it is enabled by default. I did some experiments and found some issues for Go (cgo) with the new Apple linker. Some of the issues are reported in #61190. I'm filing a new issue to track all related faulures.
warnings
Apparently the new linker is more picky. It issues some warnings that the old linker (ld64) doesn't. This includes
ld: warning: -bind_at_load is deprecated on macOS
ld: warning: search path '/usr/local/lib' not found
ld: warning: ignoring duplicate library '-lm'
ld: warning: '.../go.o' has malformed LC_DYSYMTAB, expected 92 undefined symbols to start at index 15983, found 102 undefined symbol
These are just warnings and don't affect the correctness of the build. I'm preparing CLs for fix/work around them.
offset/addend being dropped
Mostly for c-archive, c-shared, and plugin build mode, for some relocations it seems the offset/addend being dropped and the relocation is resolved to the beginning of the section. This may cause failures like SIGILL. E.g.
% go test cmd/cgo/internal/testcarchive
--- FAIL: TestInstall (1.10s)
carchive_test.go:487: [go tool cgo -objdir /var/folders/tf/nsc4z0p112vc_drrjn299ds80000gn/T/carchive_test3584575482/_obj472038228 -exportheader p.h p/p.go]
carchive_test.go:489: [go install -buildmode=c-archive ./libgo]
carchive_test.go:489: [clang -fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/tf/nsc4z0p112vc_drrjn299ds80000gn/T/go-build2775077316=/tmp/go-build -gno-record-gcc-switches -fno-common -I /var/folders/tf/nsc4z0p112vc_drrjn299ds80000gn/T/carchive_test3584575482/pkg/darwin_arm64_shared/testcarchive -o ./testp1 main.c main_unix.c /var/folders/tf/nsc4z0p112vc_drrjn299ds80000gn/T/carchive_test3584575482/pkg/darwin_arm64_shared/testcarchive/libgo.a]
carchive_test.go:489:
carchive_test.go:489: signal: illegal instruction
...
#60694 is the same failure mode.
debug info issues
The new linker doesn't generate stab symbols for our functions, causing debug info being lost. Failure look like
--- FAIL: TestDWARF (0.00s)
--- FAIL: TestDWARF/testprogcgo (3.85s)
dwarf_test.go:171: ErrUnknownPC
FAIL
FAIL cmd/link 8.822s
There is also issues with combining DWARF into executable/shared object. Currently it is affecting c-shared build mode. ld-prime rejects the shared object if we add a DWARF segment to it.
non-PIE build doesn't work (Intel Mac only)
The new linker silently ignores the -no_pie flag and generates a PIE binary, which won't work because we assumed some addresses are not relocated. CL https://go.dev/cl/461697 changes the default to PIE and CL https://go.dev/cl/511355 contains a workaround if we are asked to build a non-PIE binary.
fixes/workarounds
CL https://golang.org/cl/505415 and the stack, as well as other CLs linked in this issue, contain tentative fixes and workarounds that address some of the issues. I'll also work with Apple to have them addressed on their side.
I'm hoping o have them addressed before Apple's new linker is finally released.