[clang][clangd] Don't crash/assert on -gsplit-dwarf=single without output

[DmitryPolukhin]

Summary

The crash happens in clang::driver::tools::SplitDebugName when Output is
InputInfo::Nothing. It doesn't happen with standalone clang driver because
output is created in Driver::BuildJobsForActionNoCache.

Example backtrace:

* thread #1, name = 'clangd', stop reason = hit program assert
  * frame #0: 0x00007ffff5c4eacf libc.so.6`raise + 271
    frame #1: 0x00007ffff5c21ea5 libc.so.6`abort + 295
    frame #2: 0x00007ffff5c21d79 libc.so.6`__assert_fail_base.cold.0 + 15
    frame #3: 0x00007ffff5c47426 libc.so.6`__assert_fail + 70
    frame #4: 0x000055555dc0923c clangd`clang::driver::InputInfo::getFilename(this=0x00007fffffff9398) const at InputInfo.h:84:5
    frame #5: 0x000055555dcd0d8d clangd`clang::driver::tools::SplitDebugName(JA=0x000055555f6c6a50, Args=0x000055555f6d0b80, Input=0x00007fffffff9678, Output=0x00007fffffff9398) at CommonArgs.cpp:1275:40
    frame #6: 0x000055555dc955a5 clangd`clang::driver::tools::Clang::ConstructJob(this=0x000055555f6c69d0, C=0x000055555f6c64a0, JA=0x000055555f6c6a50, Output=0x00007fffffff9398, Inputs=0x00007fffffff9668, Args=0x000055555f6d0b80, LinkingOutput=0x0000000000000000) const at Clang.cpp:5690:33
    frame #7: 0x000055555dbf6b54 clangd`clang::driver::Driver::BuildJobsForActionNoCache(this=0x00007fffffffb5e0, C=0x000055555f6c64a0, A=0x000055555f6c6a50, TC=0x000055555f6c4be0, BoundArch=(Data = 0x0000000000000000, Length = 0), AtTopLevel=true, MultipleArchs=false, LinkingOutput=0x0000000000000000, CachedResults=size=1, TargetDeviceOffloadKind=OFK_None) const at Driver.cpp:5618:10
    frame #8: 0x000055555dbf4ef0 clangd`clang::driver::Driver::BuildJobsForAction(this=0x00007fffffffb5e0, C=0x000055555f6c64a0, A=0x000055555f6c6a50, TC=0x000055555f6c4be0, BoundArch=(Data = 0x0000000000000000, Length = 0), AtTopLevel=true, MultipleArchs=false, LinkingOutput=0x0000000000000000, CachedResults=size=1, TargetDeviceOffloadKind=OFK_None) const at Driver.cpp:5306:26
    frame #9: 0x000055555dbeb590 clangd`clang::driver::Driver::BuildJobs(this=0x00007fffffffb5e0, C=0x000055555f6c64a0) const at Driver.cpp:4844:5
    frame #10: 0x000055555dbe6b0f clangd`clang::driver::Driver::BuildCompilation(this=0x00007fffffffb5e0, ArgList=ArrayRef<const char *> @ 0x00007fffffffb268) at Driver.cpp:1496:3
    frame #11: 0x000055555b0cc0d9 clangd`clang::createInvocation(ArgList=ArrayRef<const char *> @ 0x00007fffffffbb38, Opts=CreateInvocationOptions @ 0x00007fffffffbb90) at CreateInvocationFromCommandLine.cpp:53:52
    frame #12: 0x000055555b378e7b clangd`clang::clangd::buildCompilerInvocation(Inputs=0x00007fffffffca58, D=0x00007fffffffc158, CC1Args=size=0) at Compiler.cpp:116:44
    frame #13: 0x000055555895a6c8 clangd`clang::clangd::(anonymous namespace)::Checker::buildInvocation(this=0x00007fffffffc760, TFS=0x00007fffffffe570, Contents= Has Value=false ) at Check.cpp:212:9
    frame #14: 0x0000555558959cec clangd`clang::clangd::check(File=(Data = "build/test.cpp", Length = 64), TFS=0x00007fffffffe570, Opts=0x00007fffffffe600) at Check.cpp:486:34
    frame #15: 0x000055555892164a clangd`main(argc=4, argv=0x00007fffffffecd8) at ClangdMain.cpp:993:12
    frame #16: 0x00007ffff5c3ad85 libc.so.6`__libc_start_main + 229
    frame #17: 0x00005555585bbe9e clangd`_start + 46

Test Plan: ninja ClangDriverTests && tools/clang/unittests/Driver/ClangDriverTests

[DmitryPolukhin]

Rebase and uun clang-format

[yaxunl]

clang/lib/Driver/ToolChains/CommonArgs.cpp

1277

I am wondering in what situation the Output here is not a file name. Is it possible to have a lit test for this?

[DmitryPolukhin]

clang/lib/Driver/ToolChains/CommonArgs.cpp

1277

It is possible to create lit test but still will be clangd lit test. I was not able to find case when it happens with clang driver itself. Nothing Output appears from https://github.com/llvm/llvm-project/blob/main/clang/lib/Driver/Driver.cpp#L5580 in case of clangd. In case of clang driver next else is taken and it produces file based Output. As far as I understand clangd prefers unittests over lit tests. But I can convert it to lit test if you think it is better.

[MaskRay]

Thanks for the patch! But I share the concern that the test is added to a wrong layer (https://maskray.me/blog/2021-08-08-toolchain-testing#the-test-checks-at-the-wrong-layer).

We can add a clang::createInvocation test to clang/unittests/Driver/ToolChainTest.cpp.

[DmitryPolukhin]

Moved test to clang/unittests/Driver/ToolChainTest.cpp

[DmitryPolukhin]

In D154602#4483600, @MaskRay wrote:

Thanks for the patch! But I share the concern that the test is added to a wrong layer (https://maskray.me/blog/2021-08-08-toolchain-testing#the-test-checks-at-the-wrong-layer).

We can add a clang::createInvocation test to clang/unittests/Driver/ToolChainTest.cpp.

Thank you for the suggestion. Done, please take another look.

[MaskRay]

https://maskray.me/blog/2021-08-08-toolchain-testing#the-test-checks-at-the-wrong-layer I think there is a minor "The test checks too little" issue as we can utilize the test to check a few more properties, but I am fine with this.
And I may try improving the test at spare time..

[MaskRay]

clang/unittests/Driver/ToolChainTest.cpp

371

Without a concrete target triple, the default is used. If the default target triple uses an object file format not supporting -gsplit-dwarf, this will fail.

[DmitryPolukhin]

Added -target arm-linux-gnueabi

[DmitryPolukhin]

clang/unittests/Driver/ToolChainTest.cpp

371

Oh, could you please advise how to select right target triple for the test or limit it to the case when triple I specify here is supported? I had issue in the past with triples and it was tricky to select something that makes all llvm bots happy. I added -target arm-linux-gnueabi and test seems to be working if only x86 arch is enabled.

[MaskRay]

clang/unittests/Driver/ToolChainTest.cpp

371

-target has been deprecated since Clang 3.4. Use --target=arm-linux-gnueabi.

If you just run the driver, you don't need a target in LLVM_TARGETS_TO_BUILD.
If you do code generation, LLVM_TARGETS_TO_BUILD is needed.
This is tricky, you likely need two build directories to check this...

% /tmp/out/custom1/bin/clang --target=aarch64 -c a.cc
error: unable to create target: 'No available targets are compatible with triple "aarch64"'
1 error generated.

[DmitryPolukhin]

Use --target=arm-linux-gnueabi

[DmitryPolukhin]

Run clang-format

[DmitryPolukhin]

clang/unittests/Driver/ToolChainTest.cpp

371

Yes, my driver test works fine regardless LLVM_TARGETS_TO_BUILD, also tested with -###
Will wait for build bots completion just in case and push tomorrow. Thank you for review and the detailed explanation.

clang/lib/Driver/ToolChains/CommonArgs.cpp

const char *tools::SplitDebugName(const JobAction &JA, const ArgList &Args,
                                   const InputInfo &Input,
                                   const InputInfo &Output) {
   auto AddPostfix = [JA](auto &F) {
     if (JA.getOffloadingDeviceKind() == Action::OFK_HIP)
       F += (Twine("_") + JA.getOffloadingArch()).str();
     F += ".dwo";
   };
   if (Arg *A = Args.getLastArg(options::OPT_gsplit_dwarf_EQ))
-    if (StringRef(A->getValue()) == "single")
+    if (StringRef(A->getValue()) == "single" && Output.isFilename())
       return Args.MakeArgString(Output.getFilename());
 
   SmallString<128> T;
   if (const Arg *A = Args.getLastArg(options::OPT_dumpdir)) {
     T = A->getValue();
   } else {
     Arg *FinalOutput = Args.getLastArg(options::OPT_o, options::OPT__SLASH_o);
     if (FinalOutput && Args.hasArg(options::OPT_c)) {

clang/unittests/Driver/ToolChainTest.cpp

CC->setPostCallback(
       [&](const Command &C, int Ret) { CallbackHasCalled = true; });
   const JobList &Jobs = CC->getJobs();
   auto &CmdCompile = Jobs.getJobs().front();
   const Command *FailingCmd = nullptr;
   CC->ExecuteCommand(*CmdCompile, FailingCmd);
   EXPECT_TRUE(CallbackHasCalled);
 }
 
+TEST(CompilerInvocation, SplitSwarfSingleCrash) {
+  static constexpr const char *Args[] = {
+      "clang",     "--target=arm-linux-gnueabi",
+      "-gdwarf-4", "-gsplit-dwarf=single",
+      "-c",        "foo.cpp"};
+  CreateInvocationOptions CIOpts;
+  std::unique_ptr<CompilerInvocation> CI = createInvocation(Args, CIOpts);
+  EXPECT_TRUE(CI); // no-crash
+}
+
 TEST(GetDriverMode, PrefersLastDriverMode) {
   static constexpr const char *Args[] = {"clang-cl", "--driver-mode=foo",
                                          "--driver-mode=bar", "foo.cpp"};
   EXPECT_EQ(getDriverMode(Args[0], llvm::ArrayRef(Args).slice(1)), "bar");
 }
 
 struct SimpleDiagnosticConsumer : public DiagnosticConsumer {
   void HandleDiagnostic(DiagnosticsEngine::Level DiagLevel,