[clang-repl] Add host exception support check utility flag.

Add host exception support check utility flag. This is needed to not run tests that require exception support in few buildbots that lacks related symbols for some reason.

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D129242

clang/test/Interpreter/simple-exception.cpp

@@ -0,0 +1,14 @@
+// clang-format off
+// REQUIRES: host-supports-jit, host-supports-exception 
+// UNSUPPORTED: system-aix
+// XFAIL: arm, arm64-apple, windows-msvc, windows-gnu
+// RUN: cat %s | clang-repl | FileCheck %s
+extern "C" int printf(const char *, ...);
+
+int f() { throw "Simple exception"; return 0; }
+int checkException() { try { printf("Running f()\n"); f(); } catch (const char *e) { printf("%s\n", e); } return 0; }
+auto r1 = checkException();
+// CHECK: Running f()
+// CHECK-NEXT: Simple exception
+
+%quit

clang/test/lit.cfg.py

@@ -70,7 +70,7 @@
 if config.clang_examples:
     config.available_features.add('examples')
 
-def have_host_jit_support():
+def have_host_jit_feature_support(feature_name):
     clang_repl_exe = lit.util.which('clang-repl', config.clang_tools_dir)
 
     if not clang_repl_exe:
@@ -79,7 +79,7 @@ def have_host_jit_support():
 
     try:
         clang_repl_cmd = subprocess.Popen(
-            [clang_repl_exe, '--host-supports-jit'], stdout=subprocess.PIPE)
+            [clang_repl_exe, '--host-supports-' + feature_name], stdout=subprocess.PIPE)
     except OSError:
         print('could not exec clang-repl')
         return False
@@ -89,9 +89,12 @@ def have_host_jit_support():
 
     return 'true' in clang_repl_out
 
-if have_host_jit_support():
+if have_host_jit_feature_support('jit'):
     config.available_features.add('host-supports-jit')
 
+if have_host_jit_feature_support('exception'):
+    config.available_features.add('host-supports-exception')
+
 if config.clang_staticanalyzer:
     config.available_features.add('staticanalyzer')
     tools.append('clang-check')

clang/tools/clang-repl/ClangRepl.cpp

@@ -28,6 +28,8 @@ static llvm::cl::list<std::string>
               llvm::cl::CommaSeparated);
 static llvm::cl::opt<bool> OptHostSupportsJit("host-supports-jit",
                                               llvm::cl::Hidden);
+static llvm::cl::opt<bool> OptHostSupportsException("host-supports-exception",
+                                                    llvm::cl::Hidden);
 static llvm::cl::list<std::string> OptInputs(llvm::cl::Positional,
                                              llvm::cl::desc("[code to run]"));
 
@@ -65,6 +67,42 @@ static int checkDiagErrors(const clang::CompilerInstance *CI) {
   return Errs ? EXIT_FAILURE : EXIT_SUCCESS;
 }
 
+// Check if the host environment supports c++ exception handling
+// by querying the existence of symbol __cxa_throw.
+static bool checkExceptionSupport() {
+  auto J = llvm::orc::LLJITBuilder().create();
+  if (!J) {
+    llvm::consumeError(J.takeError());
+    return false;
+  }
+
+  std::vector<const char *> Dummy;
+  auto CI = clang::IncrementalCompilerBuilder::create(Dummy);
+  if (!CI) {
+    llvm::consumeError(CI.takeError());
+    return false;
+  }
+
+  auto Interp = clang::Interpreter::create(std::move(*CI));
+  if (!Interp) {
+    llvm::consumeError(Interp.takeError());
+    return false;
+  }
+
+  if (auto Err = (*Interp)->ParseAndExecute("")) {
+    llvm::consumeError(std::move(Err));
+    return false;
+  }
+
+  auto Sym = (*Interp)->getSymbolAddress("__cxa_throw");
+  if (!Sym) {
+    llvm::consumeError(Sym.takeError());
+    return false;
+  }
+
+  return true;
+}
+
 llvm::ExitOnError ExitOnErr;
 int main(int argc, const char **argv) {
   ExitOnErr.setBanner("clang-repl: ");
@@ -87,6 +125,14 @@ int main(int argc, const char **argv) {
     return 0;
   }
 
+  if (OptHostSupportsException) {
+    if (checkExceptionSupport())
+      llvm::outs() << "true\n";
+    else
+      llvm::outs() << "false\n";
+    return 0;
+  }
+
   // FIXME: Investigate if we could use runToolOnCodeWithArgs from tooling. It
   // can replace the boilerplate code for creation of the compiler instance.
   auto CI = ExitOnErr(clang::IncrementalCompilerBuilder::create(ClangArgv));