rocksdb: Fix scan-build 'Called C++ object pointer is null' and 'Dereference of null pointer' bugs

Summary:
In the existing implementation of `ASSERT*`, test termination happens in `~Tester`, which is called when instance of `Tester` goes out of scope. This is the cause of many scan-build bugs.

This diff changes `ASSERT*` to terminate the test immediately. Also added one suppression in `util/signal_test.cc`

scan-build bugs
before: http://home.fburl.com/~sugak/latest/index.html
after: http://home.fburl.com/~sugak/latest2/index.html

Test Plan:
Modify some test to fail an assertion and make sure that `ASSERT*` terminated the test.

Run `make analyze` and make sure no 'Called C++ object pointer is null' and 'Dereference of null pointer' bugs reported.

Run tests and make sure no failing tests:
```lang=bash
% make check
% USE_CLANG=1 make check
```

Reviewers: meyering, lgalanis, sdong, rven, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D33381

util/signal_test.cc

@@ -9,8 +9,11 @@
 namespace {
 void f0() {
   char *p = nullptr;
+
+#ifndef __clang_analyzer__
   // cppcheck-suppress nullPointer
   *p = 10;  /* SIGSEGV here!! */
+#endif
 }
 
 void f1() {

util/testharness.h

@@ -46,27 +46,19 @@ extern std::string TmpDir(Env* env = Env::Default());
 // runs may be able to vary the seed.
 extern int RandomSeed();
 
+class TesterHelper;
+
 // An instance of Tester is allocated to hold temporary state during
 // the execution of an assertion.
 class Tester {
+  friend class TesterHelper;
+
  private:
   bool ok_;
-  const char* fname_;
-  int line_;
   std::stringstream ss_;
 
  public:
-  Tester(const char* f, int l)
+  Tester() : ok_(true) {}
-      : ok_(true), fname_(f), line_(l) {
-  }
-
-  ~Tester() {
-    if (!ok_) {
-      fprintf(stderr, "%s:%d:%s\n", fname_, line_, ss_.str().c_str());
-      port::PrintStack(2);
-      exit(1);
-    }
-  }
 
   Tester& Is(bool b, const char* msg) {
     if (!b) {
@@ -118,38 +110,85 @@ class Tester {
     }
     return *this;
   }
+
+  operator bool() const { return ok_; }
 };
 
-#define ASSERT_TRUE(c) ::rocksdb::test::Tester(__FILE__, __LINE__).Is((c), #c)
+class TesterHelper {
-#define ASSERT_OK(s) ::rocksdb::test::Tester(__FILE__, __LINE__).IsOk((s))
+ private:
-#define ASSERT_NOK(s) ::rocksdb::test::Tester(__FILE__, __LINE__).IsNotOk((s))
+  const char* fname_;
-#define ASSERT_EQ(a,b) ::rocksdb::test::Tester(__FILE__, __LINE__).IsEq((a),(b))
+  int line_;
-#define ASSERT_NE(a,b) ::rocksdb::test::Tester(__FILE__, __LINE__).IsNe((a),(b))
-#define ASSERT_GE(a,b) ::rocksdb::test::Tester(__FILE__, __LINE__).IsGe((a),(b))
-#define ASSERT_GT(a,b) ::rocksdb::test::Tester(__FILE__, __LINE__).IsGt((a),(b))
-#define ASSERT_LE(a,b) ::rocksdb::test::Tester(__FILE__, __LINE__).IsLe((a),(b))
-#define ASSERT_LT(a,b) ::rocksdb::test::Tester(__FILE__, __LINE__).IsLt((a),(b))
 
-#define TCONCAT(a,b) TCONCAT1(a,b)
+ public:
-#define TCONCAT1(a,b) a##b
+  TesterHelper(const char* f, int l) : fname_(f), line_(l) {}
 
-#define TEST(base,name)                                                 \
+  void operator=(const Tester& tester) {
-class TCONCAT(_Test_,name) : public base {                              \
+    fprintf(stderr, "%s:%d:%s\n", fname_, line_, tester.ss_.str().c_str());
- public:                                                                \
+    port::PrintStack(2);
-  void _Run();                                                          \
+    exit(1);
-  static void _RunIt() {                                                \
+  }
-    TCONCAT(_Test_,name) t;                                             \
+};
-    t._Run();                                                           \
+
-  }                                                                     \
+// This is trying to solve:
-};                                                                      \
+// * Evaluate expression
-bool TCONCAT(_Test_ignored_,name) =                                     \
+// * Abort the test if the evaluation is not successful with the evaluation
-  ::rocksdb::test::RegisterTest(#base, #name, &TCONCAT(_Test_,name)::_RunIt); \
+// details.
-void TCONCAT(_Test_,name)::_Run()
+// * Support operator << with ASSERT* for extra messages provided by the user
+// code of ASSERT*
+//
+// For the third, we need to make sure that an expression at the end of macro
+// supports << operator. But since we can have multiple of << we cannot abort
+// inside implementation of operator <<, as we may miss some extra message. That
+// is why there is TesterHelper with operator = which has lower precedence then
+// operator <<, and it will be called after all messages from use code are
+// accounted by <<.
+//
+// operator bool is added to Tester to make possible its declaration inside if
+// statement and do not pollute its outer scope with the name tester. But in C++
+// we cannot do any other operations inside if statement besides declaration.
+// Then in order to get inside if body there are two options: make operator
+// Tester::bool return true if ok_ == false or put the body into else part.
+#define TEST_EXPRESSION_(expression)                  \
+  if (::rocksdb::test::Tester& tester = (expression)) \
+    ;                                                 \
+  else                                                \
+  ::rocksdb::test::TesterHelper(__FILE__, __LINE__) = tester
+
+#define ASSERT_TRUE(c) TEST_EXPRESSION_(::rocksdb::test::Tester().Is((c), #c))
+#define ASSERT_OK(s) TEST_EXPRESSION_(::rocksdb::test::Tester().IsOk((s)))
+#define ASSERT_NOK(s) TEST_EXPRESSION_(::rocksdb::test::Tester().IsNotOk((s)))
+#define ASSERT_EQ(a, b) \
+  TEST_EXPRESSION_(::rocksdb::test::Tester().IsEq((a), (b)))
+#define ASSERT_NE(a, b) \
+  TEST_EXPRESSION_(::rocksdb::test::Tester().IsNe((a), (b)))
+#define ASSERT_GE(a, b) \
+  TEST_EXPRESSION_(::rocksdb::test::Tester().IsGe((a), (b)))
+#define ASSERT_GT(a, b) \
+  TEST_EXPRESSION_(::rocksdb::test::Tester().IsGt((a), (b)))
+#define ASSERT_LE(a, b) \
+  TEST_EXPRESSION_(::rocksdb::test::Tester().IsLe((a), (b)))
+#define ASSERT_LT(a, b) \
+  TEST_EXPRESSION_(::rocksdb::test::Tester().IsLt((a), (b)))
+
+#define TCONCAT(a, b) TCONCAT1(a, b)
+#define TCONCAT1(a, b) a##b
+
+#define TEST(base, name)                                              \
+  class TCONCAT(_Test_, name) : public base {                         \
+   public:                                                            \
+    void _Run();                                                      \
+    static void _RunIt() {                                            \
+      TCONCAT(_Test_, name) t;                                        \
+      t._Run();                                                       \
+    }                                                                 \
+  };                                                                  \
+  bool TCONCAT(_Test_ignored_, name) = ::rocksdb::test::RegisterTest( \
+      #base, #name, &TCONCAT(_Test_, name)::_RunIt);                  \
+  void TCONCAT(_Test_, name)::_Run()
 
 // Register the specified test.  Typically not used directly, but
 // invoked via the macro expansion of TEST.
 extern bool RegisterTest(const char* base, const char* name, void (*func)());
 
-
 }  // namespace test
 }  // namespace rocksdb