…or at least subtly different from ld64. Repro: 1. Download https://drive.google.com/file/d/1Gjrg4bQCv3uD9Ucqt4ZtroHrz5v0iCJX/view?resourcekey=0-f53UMW57gtrPlSis2sTjKg and unzip it 2. ~/src/llvm-project/out/gn/bin/ld64.lld.darwinnew @response.txt 3. ./base_unittests --gtest_filter='*Exception*' Expected: All 3 tests pass Actual: CallWithEHFrameTest.CatchExceptionHigher crashes. If you remove --color-diagnostics from response.txt and link with regular `ld`, it passes. The source of the test is here: https://source.chromium.org/chromium/chromium/src/+/master:base/mac/call_with_eh_frame_unittest.mm;l=25?q=CatchExceptionHigher&ss=chromium The implementation of CallWithEHFrame is here: https://source.chromium.org/chromium/chromium/src/+/master:base/mac/call_with_eh_frame_asm.S;bpv=1;bpt=0 It's assembly with a custom personality routine, so it's possible things are wrong in the code -- but it's been working for 5 years and it works with ld64. https://codereview.chromium.org/1212093002 has the motivation for that code.
This is not a subtle bug after all. Exceptions just don't work at all: % cat throw.cc int main() { try { throw 0; } catch (int i) { return i; } } % out/gn/bin/clang++ throw.cc -fuse-ld=lld.darwinnew lld: warning: Option `-no_deduplicate' is not yet implemented. Stay tuned... % ./a.out ; echo $? libc++abi.dylib: terminating with uncaught exception of type int zsh: abort ./a.out 134 Works fine with ld64.
ObjC exceptions also don't work: % cat throw.m int main() { @try { @throw (void*)0; } @catch (id i) { return i; } } % out/gn/bin/clang++ throw.m -framework Foundation -fuse-ld=lld.darwinnew throw.m:5:12: warning: incompatible pointer to integer conversion returning 'id' from a function with result type 'int' [-Wint-conversion] return i; ^ 1 warning generated. lld: warning: Option `-no_deduplicate' is not yet implemented. Stay tuned... % ./a.out 2021-01-10 13:09:10.871 a.out[73775:15821192] *** Terminating app due to uncaught exception of class 'nil' libc++abi.dylib: terminating with uncaught exception of type nil zsh: abort ./a.out (Also fine with ld64.)
Yeah, the `__eh_frame` support is not done yet (I was just asking gkm about it yesterday).
I see some LSDA / personality stuff landed. Is this expected to work now, or not yet?
The simple examples work, but the CallWithEHFrameTest still fails. To be precise, when linking, we hit the "too many personalities for compact unwind to encode" error. Just to see what would happen, I turned that error into a warning, and then ran the resulting binary -- CatchExceptionHigher passes, but CatchExceptionLower fails. So we're not quite there yet.
Figured it out :) https://reviews.llvm.org/D97245