Failed test `Flang :: Runtime/no-cpp-dep.c` no macOS in 13.0.1-rc2

[tru]

Hi,

While testing 13.0.1-rc2 on macOS I ran into this test error:

FAIL: Flang :: Runtime/no-cpp-dep.c (31518 of 91780)
******************** TEST 'Flang :: Runtime/no-cpp-dep.c' FAILED ********************
Script:
--
: 'RUN: at line 8';   /Users/tobias/code/llvm-releases/13.0.1/rc2/Phase2/Release/llvmCore-13.0.1-rc2.install/usr/local/bin/clang -std=c90 /Users/tobias/code/llvm-releases/13.0.1/rc2/llvm-project/flang/test/Runtime/no-cpp-dep.c -I/Users/tobias/code/llvm-releases/13.0.1/rc2/llvm-project/flang/runtime /Users/tobias/code/llvm-releases/13.0.1/rc2/Phase3/Release/llvmCore-13.0.1-rc2.obj/lib/libFortranRuntime.a -o /dev/null
--
Exit Code: 1

Command Output (stderr):
--
ld: library not found for -lSystem
clang-13: error: linker command failed with exit code 1 (use -v to see invocation)

--

This doesn't look critical - so I didn't add it into the 13.0.1 blocker column yet - but let us know if it should be fixed before release.

[llvmbot]

@llvm/issue-subscribers-flang-runtime

[tru]

This test still fails on 15.0.0-rc1.

[tru]

@banach-space @rovka any chance to get a fix for this one?

[rovka]

@tru I'm hoping to have a look, but I haven't had the time yet (I'm still trying to get the armv7 and woa binaries out and at this point that's higher priority for me, so I don't know if I'll have time to fix it before rc2 comes out, or generally in time for this release). If you're interested in having a look yourself, I can tell you that the purpose of that test is to make sure that we can link the flang runtime libraries into a C program without accidentally trying to drag in the C++ runtime. So essentially we should have a "simple" C compile line there. I don't really know what that should look like on macos and I'll probably have to look into what -lSystem is needed for and why it's not found.

[tru]

I think I am mostly interested if this could be considering a big problem and should be fixed for 15.x or if it could wait. Getting the test-suite to be clean would be nice of course, but not a requirement.

[rovka]

Ok, I think this can wait, flang isn't very mature right now so this kind of issue is probably to be expected.

[banach-space]

libSystem contains C runtime libs on MacOS. It's not easy to find this documented online. Here's a good link. Check also this message from Flang's Slack (and the corresponding thread). Basically, you may need pass something like this on MacOS for the linker to find libSystem:

-Wl,-syslibroot,/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk

Perhaps there's a more generic way, not sure.

Like @rovka , I wouldn't consider this a particularly high priority, but definitely worth fixing. I won't have any spare bandwidth this week :(

[llvmbot]

@llvm/issue-subscribers-flang-build