[clangd] Skip ClangdVFSTest.TestStackOverflow when address sanitizer is used

[bjope]

Summary

The ClangdVFSTest.TestStackOverflow unittest does not seem to work
when building the test with address sanitizer activated. Afaict the
goal is to get a constexpr depth error, rather than stack overflow.
But with asan instrumentation we do get stack overflow complaints
from asan. As a workaround this patch simply disables the test case,
when being built with address sanitizer activated.

[bjope]

I don't know if this is a good solution. But we've had problems with our downstream bots that builds llvm with asan, and runs check-all, for awhile (probably since we merged https://reviews.llvm.org/D50993).

[sammccall]

This makes sense to me. We set the thread stack size to clang::DesiredStackSize which is an empirical hardcoded number tuned for a regular build, not asan.

Thanks, and sorry for the problems!

clang-tools-extra/clangd/unittests/ClangdTests.cpp

TEST_F(ClangdVFSTest, FallbackWhenWaitingForCompileCommand) {
   ASSERT_TRUE(Server.blockUntilIdleForTest());
   EXPECT_THAT(cantFail(runCodeComplete(Server, FooCpp, Code.point(),
                                        clangd::CodeCompleteOptions()))
                   .Completions,
               ElementsAre(AllOf(Field(&CodeCompletion::Name, "xyz"),
                                 Field(&CodeCompletion::Scope, "ns::"))));
 }
 
+// Tests fails when built with asan due to stack overflow. So skip running the
+// test as a workaround.
+#if !defined(__has_feature) || !__has_feature(address_sanitizer)
 TEST_F(ClangdVFSTest, TestStackOverflow) {
   MockFSProvider FS;
   ErrorCheckingCallbacks DiagConsumer;
   MockCompilationDatabase CDB;
   ClangdServer Server(CDB, FS, ClangdServer::optsForTest(), &DiagConsumer);
 
   const char *SourceContents = R"cpp(
     constexpr int foo() { return foo(); }
     static_assert(foo());
   )cpp";
 
   auto FooCpp = testPath("foo.cpp");
   FS.Files[FooCpp] = SourceContents;
 
   Server.addDocument(FooCpp, SourceContents);
   ASSERT_TRUE(Server.blockUntilIdleForTest()) << "Waiting for diagnostics";
   // check that we got a constexpr depth error, and not crashed by stack
   // overflow
   EXPECT_TRUE(DiagConsumer.hadErrorInLastDiags());
 }
+#endif
 
 } // namespace
 } // namespace clangd
 } // namespace clang