[flang][unittest] Add unit tests for runtime's crash handler

[ashermancinelli]

These tests seem to adequately verify the runtime crash mechanism and would support other gtest tests that must catch runtime crashes.

[ashermancinelli]

@awarzynski I've actually been working on a similar patch, perhaps we could merge our efforts?

[ashermancinelli]

I have submitted D98652 to discuss similar efforts.

[awarzynski]

In D98601#2627067, @ashermancinelli wrote:

I have submitted D98652 to discuss similar efforts.

Your patch is much more thorough. I'm abandoning this in favor of D98652.

flang/unittests/RuntimeGTest/CMakeLists.txt

 add_flang_unittest(FlangRuntimeTests
   CharacterTest.cpp
+  CrashHandlerTest.cpp
 )
 
 target_link_libraries(FlangRuntimeTests
   PRIVATE
   FortranRuntime
 )

flang/unittests/RuntimeGTest/CrashHandlerTest.cpp

+//===-- flang/unittests/RuntimeGTest/CrashHandlerTest.cpp -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Tests for Fortran runtime's crash handler.
+//
+//===----------------------------------------------------------------------===//
+#include "../../runtime/terminator.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cstdarg>
+#include <cstring>
+#include <string>
+
+#include "gtest/gtest.h"
+
+using namespace Fortran::runtime;
+
+// Override the Fortran runtime's Crash()
+[[noreturn]] static void CatchCrash(
+    const char *sourceFile, int sourceLine, const char *message, va_list &ap) {
+  char buffer[1000];
+  std::vsnprintf(buffer, sizeof buffer, message, ap);
+  va_end(ap);
+  llvm::errs() << (sourceFile ? sourceFile : "unknown source file") << ":"
+               << sourceLine << ": CRASH: " << buffer << '\n';
+  std::abort();
+}
+
+TEST(CrashHandler, SanityCheck_NoSourceFile) {
+  Fortran::runtime::Terminator::RegisterCrashHandler(CatchCrash);
+  const char *fileName = nullptr;
+  Terminator terminator(fileName, /*sourceLine=*/321);
+
+  std::string expectedCrashMsg(
+      "unknown source file:321: CRASH: Hello From A Failing Test");
+  EXPECT_DEATH(terminator.Crash("Hello From A Failing Test"), expectedCrashMsg);
+}
+
+TEST(CrashHandler, SanityCheck_WithSourceFile) {
+  Fortran::runtime::Terminator::RegisterCrashHandler(CatchCrash);
+  const char *fileName = "dummy-file.f90";
+  Terminator terminator(fileName, /*sourceLine=*/123);
+
+  std::string expectedCrashMsg(
+      "dummy-file.f90:123: CRASH: Hello From A Failing Test");
+  EXPECT_DEATH(terminator.Crash("Hello From A Failing Test"),
+      "Hello From A Failing Test");
+}