macros: Add compile-time checking/inferencing for native method registration

Convert existing NATIVE_METHOD/FAST_NATIVE_METHOD macros into
also checking that the JNI signature descriptor matches the C++ function
type.

For example it matches "(J)V" with "void funcname(JNIEnv*, jclass, jlong)"
with regular native methods.

Also add several new macros:
  MAKE_JNI_[FAST_|CRITICAL_]NATIVE_METHOD - Non-convention-requiring macro.
  MAKE_JNI_[FAST_|CRITICAL_]NATIVE_METHOD_AUTOSIG - Infer signature for above.
  [FAST_|CRITICAL_]NATIVE_METHOD_AUTOSIG - Convention-requiring signature inferencing.

All of the checking/inferencing is done purely at compile time and has
zero runtime cost. If any of the checks fail there will be a compilation
error with a stack trace pointing to the reason.

See jni_macros.h for exact details on check/inference rules.

Bug: 35325126
Change-Id: I98797727ca80caf7bc462582f582b23701a1b661
Test: make -j32 JniSafeRegisterNativeMethods_test \
      && out/host/linux-x86/nativetest64/JniSafeRegisterNativeMethods_test/JniSafeRegisterNativeMethods_test
Test: make -j32  # build all of android, then see if it boots.
diff --git a/tests/JniSafeRegisterNativeMethods_test.cpp b/tests/JniSafeRegisterNativeMethods_test.cpp
new file mode 100644
index 0000000..5a1f8e9
--- /dev/null
+++ b/tests/JniSafeRegisterNativeMethods_test.cpp
@@ -0,0 +1,882 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wused-but-marked-unused"
+#pragma clang diagnostic ignored "-Wdeprecated-dynamic-exception-spec"
+#pragma clang diagnostic ignored "-Wdeprecated"
+#include <gtest/gtest.h>
+#pragma clang diagnostic pop
+#include <sstream>
+
+#define PARSE_FAILURES_NONFATAL  // return empty optionals wherever possible instead of asserting.
+#include "nativehelper/jni_macros.h"
+
+// Provide static storage to these values so they can be used in a runtime context.
+// This has to be defined local to the test translation unit to avoid ODR violations prior to C++17.
+#define STORAGE_FN_FOR_JNI_TRAITS(jtype, ...)                                  \
+constexpr char nativehelper::detail::jni_type_trait<jtype>::type_descriptor[]; \
+constexpr char nativehelper::detail::jni_type_trait<jtype>::type_name[];
+
+DEFINE_JNI_TYPE_TRAIT(STORAGE_FN_FOR_JNI_TRAITS)
+
+template <typename T>
+auto stringify_helper(const T& val) -> decltype(std::stringstream().str()) {  // suppress incorrect warnings about compiler not support 'auto'
+  std::stringstream ss;
+  ss << val;
+  return ss.str();
+}
+
+#define EXPECT_STRINGIFY_EQ(x, y) EXPECT_EQ(stringify_helper(x), stringify_helper(y))
+
+TEST(JniSafeRegisterNativeMethods, StringParsing) {
+  using namespace nativehelper::detail;                                \
+
+  // Super basic bring-up tests for core functionality.
+
+  {
+    constexpr ConstexprStringView v_str = "V";
+    EXPECT_EQ(1u, v_str.size());
+    EXPECT_EQ(false, v_str.empty());
+
+    std::stringstream ss;
+    ss << v_str;
+    EXPECT_EQ("V", ss.str());
+  }
+
+  {
+    auto parse = ParseSingleTypeDescriptor("", /*allow_void*/true);
+    EXPECT_EQ("", parse->token);
+    EXPECT_EQ("", parse->remainder);
+  }
+
+  {
+    auto parse = ParseSingleTypeDescriptor("V", /*allow_void*/true);
+    EXPECT_EQ("V", parse->token);
+    EXPECT_EQ("", parse->remainder);
+  }
+
+  {
+    auto parse = ParseSingleTypeDescriptor("[I");
+    EXPECT_EQ("[I", parse->token);
+    EXPECT_EQ("", parse->remainder);
+  }
+
+  // Stringify is used for convenience to make writing out tests easier.
+  // Transforms as "(XYZ)W" -> "args={X,Y,Z}, ret=W"
+
+#define PARSE_SIGNATURE_AS_LIST(str) (ParseSignatureAsList<sizeof(str)>(str))
+
+  {
+    constexpr auto jni_descriptor = PARSE_SIGNATURE_AS_LIST("()V");
+    EXPECT_STRINGIFY_EQ("args={}, ret=V", jni_descriptor);
+  }
+
+  {
+    constexpr auto
+        jni_descriptor = PARSE_SIGNATURE_AS_LIST("()Ljava/lang/Object;");
+    EXPECT_STRINGIFY_EQ("args={}, ret=Ljava/lang/Object;", jni_descriptor);
+  }
+
+  {
+    constexpr auto jni_descriptor = PARSE_SIGNATURE_AS_LIST("()[I");
+    EXPECT_STRINGIFY_EQ("args={}, ret=[I", jni_descriptor);
+  }
+
+#define EXPECT_OK_SIGNATURE_PARSE(signature, args, ret) \
+  do { \
+    constexpr auto jni_descriptor = PARSE_SIGNATURE_AS_LIST(signature); \
+    EXPECT_EQ(true, jni_descriptor.has_value());                        \
+    EXPECT_STRINGIFY_EQ("args={" args "}, ret=" ret, jni_descriptor);   \
+  } while (0)
+
+  // Exhaustive tests for successful parsing.
+
+  EXPECT_OK_SIGNATURE_PARSE("()V", /*args*/"", /*ret*/"V");
+  EXPECT_OK_SIGNATURE_PARSE("()Z", /*args*/"", /*ret*/"Z");
+  EXPECT_OK_SIGNATURE_PARSE("()B", /*args*/"", /*ret*/"B");
+  EXPECT_OK_SIGNATURE_PARSE("()C", /*args*/"", /*ret*/"C");
+  EXPECT_OK_SIGNATURE_PARSE("()S", /*args*/"", /*ret*/"S");
+  EXPECT_OK_SIGNATURE_PARSE("()I", /*args*/"", /*ret*/"I");
+  EXPECT_OK_SIGNATURE_PARSE("()F", /*args*/"", /*ret*/"F");
+  EXPECT_OK_SIGNATURE_PARSE("()J", /*args*/"", /*ret*/"J");
+  EXPECT_OK_SIGNATURE_PARSE("()D", /*args*/"", /*ret*/"D");
+  EXPECT_OK_SIGNATURE_PARSE("()Ljava/lang/Object;", /*args*/
+                            "", /*ret*/
+                            "Ljava/lang/Object;");
+  EXPECT_OK_SIGNATURE_PARSE("()[Ljava/lang/Object;", /*args*/
+                            "", /*ret*/
+                            "[Ljava/lang/Object;");
+  EXPECT_OK_SIGNATURE_PARSE("()[I", /*args*/"", /*ret*/"[I");
+  EXPECT_OK_SIGNATURE_PARSE("()[[I", /*args*/"", /*ret*/"[[I");
+  EXPECT_OK_SIGNATURE_PARSE("()[[[I", /*args*/"", /*ret*/"[[[I");
+
+
+  EXPECT_OK_SIGNATURE_PARSE("(Z)V", /*args*/"Z", /*ret*/"V");
+  EXPECT_OK_SIGNATURE_PARSE("(B)V", /*args*/"B", /*ret*/"V");
+  EXPECT_OK_SIGNATURE_PARSE("(C)D", /*args*/"C", /*ret*/"D");
+  EXPECT_OK_SIGNATURE_PARSE("(S)V", /*args*/"S", /*ret*/"V");
+  EXPECT_OK_SIGNATURE_PARSE("(I)V", /*args*/"I", /*ret*/"V");
+  EXPECT_OK_SIGNATURE_PARSE("(F)V", /*args*/"F", /*ret*/"V");
+  EXPECT_OK_SIGNATURE_PARSE("(J)F", /*args*/"J", /*ret*/"F");
+  EXPECT_OK_SIGNATURE_PARSE("(D)V", /*args*/"D", /*ret*/"V");
+  EXPECT_OK_SIGNATURE_PARSE("(Ljava/lang/Object;)V", "Ljava/lang/Object;", "V");
+  EXPECT_OK_SIGNATURE_PARSE("([Ljava/lang/Object;)V",
+                            "[Ljava/lang/Object;",
+                            "V");
+  EXPECT_OK_SIGNATURE_PARSE("([I)V", /*ret*/"[I", "V");
+  EXPECT_OK_SIGNATURE_PARSE("([[I)V", /*ret*/"[[I", "V");
+  EXPECT_OK_SIGNATURE_PARSE("([[[I)V", /*ret*/"[[[I", "V");
+
+  EXPECT_OK_SIGNATURE_PARSE("(ZIJ)V", /*args*/"Z,I,J", /*ret*/"V");
+  EXPECT_OK_SIGNATURE_PARSE("(B[IJ)V", /*args*/"B,[I,J", /*ret*/"V");
+  EXPECT_OK_SIGNATURE_PARSE("(Ljava/lang/Object;B)D", /*args*/
+                            "Ljava/lang/Object;,B", /*ret*/
+                            "D");
+  EXPECT_OK_SIGNATURE_PARSE("(Ljava/lang/Object;Ljava/lang/String;IF)D", /*args*/
+                            "Ljava/lang/Object;,Ljava/lang/String;,I,F", /*ret*/
+                            "D");
+  EXPECT_OK_SIGNATURE_PARSE("([[[Ljava/lang/Object;Ljava/lang/String;IF)D", /*args*/
+                            "[[[Ljava/lang/Object;,Ljava/lang/String;,I,F", /*ret*/
+                            "D");
+
+  /*
+   * Test Failures in Parsing
+   */
+
+#define EXPECT_FAILED_SIGNATURE_PARSE(jni_descriptor) \
+  EXPECT_STRINGIFY_EQ(ConstexprOptional<JniSignatureDescriptor<sizeof(jni_descriptor)>>{},\
+                      ParseSignatureAsList<sizeof(jni_descriptor)>(jni_descriptor))
+
+  // For the failures to work we must turn off 'PARSE_FAILURES_FATAL'.
+  // Otherwise they immediately cause a crash, which is actually the desired behavior
+  // when this is used by the end-user in REGISTER_NATIVE_METHOD.
+  {
+    EXPECT_FAILED_SIGNATURE_PARSE("");
+    EXPECT_FAILED_SIGNATURE_PARSE("A");
+    EXPECT_FAILED_SIGNATURE_PARSE(")");
+    EXPECT_FAILED_SIGNATURE_PARSE("V");
+    EXPECT_FAILED_SIGNATURE_PARSE("(");
+    EXPECT_FAILED_SIGNATURE_PARSE("(A");
+    EXPECT_FAILED_SIGNATURE_PARSE("()");
+    EXPECT_FAILED_SIGNATURE_PARSE("()A");
+    EXPECT_FAILED_SIGNATURE_PARSE("()VV");
+    EXPECT_FAILED_SIGNATURE_PARSE("()L");
+    EXPECT_FAILED_SIGNATURE_PARSE("()L;");
+    EXPECT_FAILED_SIGNATURE_PARSE("()BAD;");
+    EXPECT_FAILED_SIGNATURE_PARSE("()Ljava/lang/Object");
+    EXPECT_FAILED_SIGNATURE_PARSE("()Ljava/lang/Object;X");
+
+    EXPECT_FAILED_SIGNATURE_PARSE("(V)V");
+    EXPECT_FAILED_SIGNATURE_PARSE("(ILcat)V");
+    EXPECT_FAILED_SIGNATURE_PARSE("([dog)V");
+    EXPECT_FAILED_SIGNATURE_PARSE("(IV)V");
+    EXPECT_FAILED_SIGNATURE_PARSE("([V)V");
+    EXPECT_FAILED_SIGNATURE_PARSE("([[V)V");
+    EXPECT_FAILED_SIGNATURE_PARSE("()v");
+    EXPECT_FAILED_SIGNATURE_PARSE("()i");
+    EXPECT_FAILED_SIGNATURE_PARSE("()f");
+  }
+
+}
+
+#define EXPECT_IS_VALID_JNI_ARGUMENT_TYPE(expected, expr) \
+ { constexpr bool is_valid = (expr); \
+   EXPECT_EQ(expected, is_valid) << #expr; \
+ }
+
+// Basic smoke tests for parameter validity.
+// See below for more exhaustive tests.
+TEST(JniSafeRegisterNativeMethods, ParameterTypes) {
+  using namespace nativehelper::detail;
+  EXPECT_TRUE(IsJniParameterCountValid(kCriticalNative, 0u));
+  EXPECT_TRUE(IsJniParameterCountValid(kCriticalNative, 1u));
+  EXPECT_TRUE(IsJniParameterCountValid(kCriticalNative, 2u));
+  EXPECT_TRUE(IsJniParameterCountValid(kCriticalNative, 3u));
+  EXPECT_TRUE(IsJniParameterCountValid(kCriticalNative, 4u));
+
+  EXPECT_FALSE(IsJniParameterCountValid(kNormalNative, 0u));
+  EXPECT_FALSE(IsJniParameterCountValid(kNormalNative, 1u));
+  EXPECT_TRUE(IsJniParameterCountValid(kNormalNative, 2u));
+  EXPECT_TRUE(IsJniParameterCountValid(kNormalNative, 3u));
+  EXPECT_TRUE(IsJniParameterCountValid(kNormalNative, 4u));
+
+  EXPECT_TRUE((IsValidJniParameter<void>(kNormalNative, kReturnPosition)));
+  EXPECT_IS_VALID_JNI_ARGUMENT_TYPE(true,(is_valid_jni_argument_type<kNormalNative, /*pos*/0u, JNIEnv*>::value));
+  EXPECT_IS_VALID_JNI_ARGUMENT_TYPE(true,(is_valid_jni_argument_type<kNormalNative, /*pos*/1u, jobject>::value));
+  EXPECT_IS_VALID_JNI_ARGUMENT_TYPE(true,(is_valid_jni_argument_type<kNormalNative, /*pos*/1u, jclass>::value));
+  EXPECT_IS_VALID_JNI_ARGUMENT_TYPE(false,(is_valid_jni_argument_type<kNormalNative, /*pos*/1u, jstring>::value));
+}
+
+struct TestReturnAnything {
+  template <typename T>
+  operator T() const {
+    return T{};
+  }
+};
+
+namespace test_jni {
+  void empty_fn() {}
+}
+struct TestJni {
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-parameter"
+
+  // Always bad.
+  static void bad_cptr(const char* ptr) {}
+  static void* bad_ret_ptr() { return nullptr; }
+  static JNIEnv* bad_ret_env() { return nullptr; }
+  static void bad_wrongplace_env(jobject, JNIEnv*) {}
+  static void bad_wrongplace_env2(jobject, jobject, JNIEnv*) {}
+  static void v_e(JNIEnv*) {}
+  static void v_ei(JNIEnv*, jint l) {}
+  static void v_el(JNIEnv*, jlong l) {}
+  static void v_et(JNIEnv*, jstring) {}
+  static jobject o_none() { return nullptr; }
+  static void bad_noref_jint_norm(JNIEnv*, jclass, jint&) {}
+  static void bad_noref_jint_crit(jint&) {}
+
+  // Good depending on the context:
+
+  // CriticalNative
+  static void empty_fn() {}
+  static jint int_fn() { return 0; }
+
+  static void v_() {}
+  static void v_vol_i(volatile jint) {}
+  static void v_const_i(const jint) {}
+  static void v_i(jint) {}
+  static void v_l(jlong) {}
+  static void v_lib(jlong, jint, jboolean) {}
+  static jshort s_lib(jlong, jint, jboolean) { return 0; }
+
+  // Normal or FastNative.
+  static void v_eo(JNIEnv*, jobject) {}
+  static void v_eoo(JNIEnv*, jobject, jobject) {}
+  static void v_ek(JNIEnv*, jclass) {}
+  static void v_eolib(JNIEnv*, jobject, jlong, jint, jboolean) {}
+  static jshort s_eolAibA(JNIEnv*, jobject, jlongArray, jint, jbooleanArray) { return 0; }
+
+#define DEC_TEST_FN_IMPL(name, ret_t, ...) \
+  static ret_t name (__VA_ARGS__) { return TestReturnAnything{}; }
+
+#define DEC_TEST_FN(name, correct, ret_t, ...) \
+  DEC_TEST_FN_IMPL(normal_ ## name, ret_t, JNIEnv*, jobject, __VA_ARGS__) \
+  DEC_TEST_FN_IMPL(normal2_ ## name, ret_t, JNIEnv*, jclass, __VA_ARGS__) \
+  DEC_TEST_FN_IMPL(critical_ ## name, ret_t, __VA_ARGS__)
+
+#define DEC_TEST_FN0(name, correct, ret_t) \
+  DEC_TEST_FN_IMPL(normal_ ## name, ret_t, JNIEnv*, jobject) \
+  DEC_TEST_FN_IMPL(normal2_ ## name, ret_t, JNIEnv*, jclass) \
+  DEC_TEST_FN_IMPL(critical_ ## name, ret_t)
+
+#define JNI_TEST_FN(FN, FN0) \
+  FN0(a0,CRITICAL,void) \
+  FN0(a ,CRITICAL,jboolean) \
+  FN0(a1,CRITICAL,jbyte) \
+  FN0(g, CRITICAL,jchar) \
+  FN0(c, CRITICAL,jshort) \
+  FN0(b, CRITICAL,jint) \
+  FN0(f, CRITICAL,jlong) \
+  FN0(d, CRITICAL,jfloat) \
+  FN0(e, CRITICAL,jdouble) \
+  FN0(f2,NORMAL  ,jobject) \
+  FN0(f3,NORMAL  ,jclass) \
+  FN0(fr,NORMAL  ,jstring) \
+  FN0(fa,NORMAL  ,jarray) \
+  FN0(fb,NORMAL  ,jobjectArray) \
+  FN0(fc,NORMAL  ,jbooleanArray) \
+  FN0(fd,NORMAL  ,jcharArray) \
+  FN0(fe,NORMAL  ,jshortArray) \
+  FN0(ff,NORMAL  ,jintArray) \
+  FN0(fg,NORMAL  ,jlongArray) \
+  FN0(fk,NORMAL  ,jfloatArray) \
+  FN0(fi,NORMAL  ,jdoubleArray) \
+  FN0(fl,NORMAL  ,jthrowable) \
+  FN(aa, CRITICAL,jboolean,jboolean) \
+  FN(ax, CRITICAL,jbyte,jbyte) \
+  FN(ag, CRITICAL,jchar,jchar) \
+  FN(ac, CRITICAL,jshort,jshort) \
+  FN(ac2,CRITICAL,jshort,jshort,jchar) \
+  FN(ab, CRITICAL,jint,jint) \
+  FN(af, CRITICAL,jlong,jlong) \
+  FN(ad, CRITICAL,jfloat,jfloat) \
+  FN(ae, CRITICAL,jdouble,jdouble) \
+  FN(af2,NORMAL  ,jobject,jobject) \
+  FN(af3,NORMAL  ,jclass,jclass) \
+  FN(afr,NORMAL  ,jstring,jstring) \
+  FN(afa,NORMAL  ,jarray,jarray) \
+  FN(afb,NORMAL  ,jobjectArray,jobjectArray) \
+  FN(afc,NORMAL  ,jbooleanArray,jbooleanArray) \
+  FN(afd,NORMAL  ,jcharArray,jcharArray) \
+  FN(afe,NORMAL  ,jshortArray,jshortArray) \
+  FN(aff,NORMAL  ,jintArray,jintArray) \
+  FN(afg,NORMAL  ,jlongArray,jlongArray) \
+  FN(afk,NORMAL  ,jfloatArray,jfloatArray) \
+  FN(afi,NORMAL  ,jdoubleArray,jdoubleArray) \
+  FN(agi,NORMAL  ,jdoubleArray,jdoubleArray,jobject) \
+  FN(afl,NORMAL  ,jthrowable,jthrowable) \
+  \
+  FN0(z0,ILLEGAL ,JNIEnv*) \
+  FN(z1, ILLEGAL ,void, JNIEnv*) \
+  FN(z2, ILLEGAL ,JNIEnv*, JNIEnv*) \
+  FN(z3, ILLEGAL ,void, void*) \
+  FN0(z4,ILLEGAL ,void*) \
+
+#define JNI_TEST_FN_BOTH(x) JNI_TEST_FN(x,x)
+
+// we generate a return statement because some functions are non-void.
+// disable the useless warning about returning from a non-void function.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wreturn-type"
+  JNI_TEST_FN(DEC_TEST_FN, DEC_TEST_FN0);
+#pragma clang diagnostic pop
+
+  // TODO: probably should be an x-macro table
+  // and that way we can add critical/normal to it as well
+  // and also the type descriptor, and reuse this for multiple tests.
+
+#pragma clang diagnostic pop
+};
+// Note: Using function-local structs does not work.
+// Template parameters must have linkage, which function-local structs lack.
+
+TEST(JniSafeRegisterNativeMethods, FunctionTypes) {
+  using namespace nativehelper::detail;
+  // The exact error messages are not tested but they would be seen in the compiler
+  // stack trace when used from a constexpr context.
+
+#define IS_VALID_JNI_FUNCTION_TYPE(native_kind, func) (IsValidJniFunctionType<native_kind, decltype(func), (func)>())
+#define IS_VALID_NORMAL_JNI_FUNCTION_TYPE(func) IS_VALID_JNI_FUNCTION_TYPE(kNormalNative, func)
+#define IS_VALID_CRITICAL_JNI_FUNCTION_TYPE(func) IS_VALID_JNI_FUNCTION_TYPE(kCriticalNative, func)
+
+#define EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(func)                      \
+    do {                                                            \
+       EXPECT_FALSE(IS_VALID_CRITICAL_JNI_FUNCTION_TYPE(func));    \
+       EXPECT_FALSE(IS_VALID_NORMAL_JNI_FUNCTION_TYPE(func));      \
+    } while (false)
+
+#define EXPECT_EITHER_JNI_FUNCTION_TYPE(func)                       \
+    do {                                                            \
+       EXPECT_TRUE(IS_VALID_CRITICAL_JNI_FUNCTION_TYPE(func));     \
+       EXPECT_TRUE(IS_VALID_NORMAL_JNI_FUNCTION_TYPE(func));       \
+    } while (false)
+
+#define EXPECT_NORMAL_JNI_FUNCTION_TYPE(func)                       \
+    do {                                                            \
+       EXPECT_FALSE(IS_VALID_CRITICAL_JNI_FUNCTION_TYPE(func));    \
+       EXPECT_TRUE(IS_VALID_NORMAL_JNI_FUNCTION_TYPE(func));       \
+    } while (false)
+
+#define EXPECT_CRITICAL_JNI_FUNCTION_TYPE(func)                    \
+  do {                                                             \
+     EXPECT_TRUE(IS_VALID_CRITICAL_JNI_FUNCTION_TYPE(func));      \
+     EXPECT_FALSE(IS_VALID_NORMAL_JNI_FUNCTION_TYPE(func));       \
+  } while (false)
+
+  {
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::bad_cptr);
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::bad_ret_ptr);
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::bad_ret_env);
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::bad_wrongplace_env);
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::bad_wrongplace_env2);
+
+    EXPECT_CRITICAL_JNI_FUNCTION_TYPE(TestJni::empty_fn);
+    EXPECT_CRITICAL_JNI_FUNCTION_TYPE(test_jni::empty_fn);
+    EXPECT_CRITICAL_JNI_FUNCTION_TYPE(TestJni::int_fn);
+
+    EXPECT_CRITICAL_JNI_FUNCTION_TYPE(TestJni::v_);
+    EXPECT_CRITICAL_JNI_FUNCTION_TYPE(TestJni::v_vol_i);
+    EXPECT_CRITICAL_JNI_FUNCTION_TYPE(TestJni::v_const_i);
+    EXPECT_CRITICAL_JNI_FUNCTION_TYPE(TestJni::v_i);
+    EXPECT_CRITICAL_JNI_FUNCTION_TYPE(TestJni::v_l);
+
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::v_e);
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::v_ei);
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::v_el);
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::v_et);
+
+    EXPECT_NORMAL_JNI_FUNCTION_TYPE(TestJni::v_eo);
+    EXPECT_NORMAL_JNI_FUNCTION_TYPE(TestJni::v_ek);
+
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::o_none);
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::bad_noref_jint_norm);
+    EXPECT_ILLEGAL_JNI_FUNCTION_TYPE(TestJni::bad_noref_jint_crit);
+  }
+
+  enum class TestJniKind {
+    ILLEGAL,
+    NORMAL,
+    CRITICAL
+  };
+
+  // ILLEGAL signatures are always illegal.
+  bool kExpected_ILLEGAL_against_NORMAL = false;
+  bool kExpected_ILLEGAL_against_CRITICAL = false;
+  // NORMAL signatures are only legal for Normal JNI.
+  bool kExpected_NORMAL_against_NORMAL = true;
+  bool kExpected_NORMAL_against_CRITICAL = false;
+  // CRITICAL signatures are legal for both Normal+Critical JNI.
+  bool kExpected_CRITICAL_against_CRITICAL = true;
+  bool kExpected_CRITICAL_against_NORMAL = true;
+  // Note that we munge normal and critical type signatures separately
+  // and that a normal_ prefixed is always a bad critical signature,
+  // and a critical_ prefixed signature is always a bad normal signature.
+  // See JNI_TEST_FN_MAKE_TEST for the implementation of this logic.
+
+#undef EXPECTED_FOR
+#define EXPECTED_FOR(jni_kind, context) \
+  (kExpected_ ## jni_kind ## _against_ ## context)
+
+  {
+#define JNI_TEST_FN_MAKE_TEST(name, jni_kind, ...) \
+     do {                                                            \
+       EXPECT_EQ(EXPECTED_FOR(jni_kind, NORMAL),                     \
+                 IS_VALID_NORMAL_JNI_FUNCTION_TYPE(TestJni::normal_ ## name));  \
+       EXPECT_FALSE(IS_VALID_CRITICAL_JNI_FUNCTION_TYPE(TestJni::normal_ ## name)); \
+       EXPECT_EQ(EXPECTED_FOR(jni_kind, NORMAL),                     \
+                 IS_VALID_NORMAL_JNI_FUNCTION_TYPE(TestJni::normal2_ ## name)); \
+       EXPECT_FALSE(IS_VALID_CRITICAL_JNI_FUNCTION_TYPE(TestJni::normal2_ ## name)); \
+       EXPECT_EQ(EXPECTED_FOR(jni_kind, CRITICAL),                   \
+                 IS_VALID_CRITICAL_JNI_FUNCTION_TYPE(TestJni::critical_ ## name)); \
+       EXPECT_FALSE(IS_VALID_NORMAL_JNI_FUNCTION_TYPE(TestJni::critical_ ## name)); \
+    } while (false);
+
+    JNI_TEST_FN_BOTH(JNI_TEST_FN_MAKE_TEST);
+  }
+}
+
+#define EXPECT_CONSTEXPR_EQ(lhs, rhs) \
+ { constexpr auto lhs_val = (lhs);    \
+   constexpr auto rhs_val = (rhs);    \
+   EXPECT_EQ(lhs_val, rhs_val) << "LHS: " << #lhs << ", RHS: " << #rhs; \
+ }
+
+TEST(JniSafeRegisterNativeMethods, FunctionTypeDescriptorConversion) {
+  using namespace nativehelper::detail;
+  {
+    constexpr auto cvrt = MaybeMakeReifiedJniSignature<kCriticalNative,
+                                                       decltype(TestJni::v_i),
+                                                       TestJni::v_i>();
+    EXPECT_TRUE(cvrt.has_value());
+    EXPECT_CONSTEXPR_EQ(2u, cvrt->max_size);
+    EXPECT_CONSTEXPR_EQ(1u, cvrt->args.size());
+    EXPECT_STRINGIFY_EQ("args={jint}, ret=void", cvrt.value());
+  }
+
+  {
+    constexpr auto cvrt = MaybeMakeReifiedJniSignature<kNormalNative,
+                                                       decltype(TestJni::v_i),
+                                                       TestJni::v_i>();
+    EXPECT_FALSE(cvrt.has_value());
+  }
+
+  {
+    constexpr auto cvrt = MaybeMakeReifiedJniSignature<kNormalNative,
+                                                       decltype(TestJni::normal_agi),
+                                                       TestJni::normal_agi>();
+    EXPECT_TRUE(cvrt.has_value());
+    EXPECT_EQ(2u, cvrt->args.size());
+    EXPECT_STRINGIFY_EQ("args={jdoubleArray,jobject}, ret=jdoubleArray", cvrt.value());
+  }
+
+  {
+    constexpr auto cvrt = MaybeMakeReifiedJniSignature<kCriticalNative,
+                                                       decltype(TestJni::critical_ac2),
+                                                       TestJni::critical_ac2>();
+    EXPECT_TRUE(cvrt.has_value());
+    EXPECT_EQ(2u, cvrt->args.size());
+    EXPECT_STRINGIFY_EQ("args={jshort,jchar}, ret=jshort", cvrt.value());
+  }
+
+  // TODO: use JNI_TEST_FN to generate these tests automatically.
+}
+
+struct test_function_traits {
+  static int int_returning_function() { return 0; }
+};
+
+template <typename T>
+struct apply_return_type {
+  constexpr int operator()() const {
+    return sizeof(T) == sizeof(int);
+  }
+};
+
+#define FN_ARGS_PAIR(fn) decltype(fn), (fn)
+
+TEST(JniSafeRegisterNativeMethods, FunctionTraits) {
+  using namespace nativehelper::detail;
+  using traits_for_int_ret = FunctionTypeMetafunction<FN_ARGS_PAIR(test_function_traits::int_returning_function)>;
+  int applied = traits_for_int_ret::map_return<apply_return_type>();
+  EXPECT_EQ(1, applied);
+
+  auto arr = traits_for_int_ret::map_args<apply_return_type>();
+  EXPECT_EQ(0u, arr.size());
+}
+
+struct IntHolder {
+  int value;
+};
+
+constexpr int GetTestValue(const IntHolder& i) {
+  return i.value;
+}
+
+constexpr int GetTestValue(int i) {
+  return i;
+}
+
+template <typename T, size_t kMaxSize>
+constexpr size_t SumUpVector(const nativehelper::detail::ConstexprVector<T, kMaxSize>& vec) {
+  size_t s = 0;
+  for (const T& elem : vec) {
+    s += static_cast<size_t>(GetTestValue(elem));
+  }
+  return s;
+}
+
+template <typename T>
+constexpr auto make_test_int_vector() {
+  using namespace nativehelper::detail;
+  ConstexprVector<T, 5> vec_int;
+  vec_int.push_back(T{1});
+  vec_int.push_back(T{2});
+  vec_int.push_back(T{3});
+  vec_int.push_back(T{4});
+  vec_int.push_back(T{5});
+  return vec_int;
+}
+
+TEST(JniSafeRegisterNativeMethods, ConstexprVector) {
+  using namespace nativehelper::detail;
+  {
+    constexpr ConstexprVector<IntHolder, 5> vec_int = make_test_int_vector<IntHolder>();
+    constexpr size_t the_sum = SumUpVector(vec_int);
+    EXPECT_EQ(15u, the_sum);
+  }
+
+  {
+    constexpr ConstexprVector<int, 5> vec_int = make_test_int_vector<int>();
+    constexpr size_t the_sum = SumUpVector(vec_int);
+    EXPECT_EQ(15u, the_sum);
+  }
+}
+
+// Need this intermediate function to make a JniDescriptorNode from a string literal.
+// C++ doesn't do implicit conversion through two+ type constructors.
+constexpr nativehelper::detail::JniDescriptorNode MakeNode(
+    nativehelper::detail::ConstexprStringView str) {
+  return nativehelper::detail::JniDescriptorNode{str};
+}
+
+#define EXPECT_EQUALISH_JNI_DESCRIPTORS_IMPL(user_desc, derived, cond) \
+  do { \
+    constexpr bool res = CompareJniDescriptorNodeErased(MakeNode(user_desc), ReifiedJniTypeTrait::Reify<derived>()); \
+    (void)res; \
+    EXPECT_ ## cond(CompareJniDescriptorNodeErased(MakeNode(user_desc), ReifiedJniTypeTrait::Reify<derived>())); \
+  } while (0);
+
+#define EXPECT_EQUALISH_JNI_DESCRIPTORS(user_desc, derived_desc) \
+  EXPECT_EQUALISH_JNI_DESCRIPTORS_IMPL(user_desc, derived_desc, TRUE)
+
+#define EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS(user_desc, derived_desc) \
+  EXPECT_EQUALISH_JNI_DESCRIPTORS_IMPL(user_desc, derived_desc, FALSE)
+
+TEST(JniSafeRegisterNativeMethods, CompareJniDescriptorNodeErased) {
+  using namespace nativehelper::detail;
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("V", void);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("V", jint);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Z", jboolean);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Z", void);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Z", jobject);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("J", jlong);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("J", jobject);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("J", jthrowable);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("J", jint);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/String;", jstring);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Class;", jclass);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Object;", jobject);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Integer;", jobject);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("[Z", jthrowable);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("[Z", jobjectArray);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Integer;", jintArray);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Integer;", jarray);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Integer;", jarray);
+
+  // Stricter checks.
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Object;", jobjectArray);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/String;", jobject);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Class;", jobject);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("[Z", jobject);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("[Ljava/lang/Object;", jobject);
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Object;", jarray);
+
+  // Permissive checks that are weaker than normal.
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Exception;", jobject);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Error;", jobject);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("[Z", jarray);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("[I", jarray);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("[[Z", jarray);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("[[Ljava/lang/Object;", jarray);
+
+  // jthrowable-related checks.
+  EXPECT_NOT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Throwable;", jobject);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Throwable;", jthrowable);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Exception;", jthrowable);
+  EXPECT_EQUALISH_JNI_DESCRIPTORS("Ljava/lang/Error;", jthrowable);
+}
+
+#define EXPECT_SIMILAR_TYPE_DESCRIPTOR_MATCH(type_desc, type) \
+  do { \
+    constexpr auto res = ReifiedJniTypeTrait::MostSimilarTypeDescriptor(type_desc); \
+    EXPECT_TRUE((ReifiedJniTypeTrait::MostSimilarTypeDescriptor(type_desc)).has_value());\
+    if (res.has_value()) EXPECT_EQ(ReifiedJniTypeTrait::Reify<type>(), res.value());  \
+  } while (false)
+
+#define EXPECT_SIMILAR_TYPE_DESCRIPTOR_NO_MATCH(type_desc) \
+  do { \
+    auto res = ReifiedJniTypeTrait::MostSimilarTypeDescriptor(type_desc); \
+    EXPECT_FALSE(res.has_value());                                        \
+  } while (false)
+
+#define JNI_TYPE_TRAIT_MUST_BE_SAME_FN(type_name, type_desc, ...)              \
+  /* skip jarray because it aliases Ljava/lang/Object; */                      \
+  do {                                                                         \
+    constexpr auto str_type_name = ConstexprStringView(#type_name);          \
+    if (str_type_name != "jarray" && str_type_name != "JNIEnv*") {             \
+      EXPECT_SIMILAR_TYPE_DESCRIPTOR_MATCH(type_desc, type_name);              \
+    }                                                                          \
+  } while(false);
+
+TEST(JniSafeRegisterNativeMethods, MostSimilarTypeDescriptor) {
+  using namespace nativehelper::detail;
+  EXPECT_SIMILAR_TYPE_DESCRIPTOR_MATCH("Z", jboolean);
+  EXPECT_SIMILAR_TYPE_DESCRIPTOR_MATCH("[[I", jobjectArray);
+  EXPECT_SIMILAR_TYPE_DESCRIPTOR_MATCH("[[Z", jobjectArray);
+  EXPECT_SIMILAR_TYPE_DESCRIPTOR_MATCH("[Ljava/lang/String;", jobjectArray);
+  EXPECT_SIMILAR_TYPE_DESCRIPTOR_MATCH("[Ljava/lang/Integer;", jobjectArray);
+  EXPECT_SIMILAR_TYPE_DESCRIPTOR_NO_MATCH("illegal");
+  EXPECT_SIMILAR_TYPE_DESCRIPTOR_NO_MATCH("?");
+  EXPECT_SIMILAR_TYPE_DESCRIPTOR_NO_MATCH("");
+
+  DEFINE_JNI_TYPE_TRAIT(JNI_TYPE_TRAIT_MUST_BE_SAME_FN);
+}
+
+#define ENFORCE_CONSTEXPR(expr) \
+  static_assert(__builtin_constant_p(expr), "Expression must be constexpr")
+
+#define EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION_IMPL(cond, native_kind, func, desc) \
+  do {                                                                        \
+    ENFORCE_CONSTEXPR((MatchJniDescriptorWithFunctionType<                    \
+        native_kind,                                                          \
+        decltype(func),                                                       \
+        func,                                                                 \
+        sizeof(desc)>(desc)));                                                \
+    EXPECT_ ## cond((MatchJniDescriptorWithFunctionType<                      \
+        native_kind,                                                          \
+        decltype(func),                                                       \
+        func,                                                                 \
+        sizeof(desc)>(desc)));                                                \
+  } while(0)
+
+#define EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(native_kind, func, desc) \
+    EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION_IMPL(TRUE, native_kind, func, desc)
+
+#define EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(native_kind, func, desc) \
+    EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION_IMPL(FALSE, native_kind, func, desc)
+
+TEST(JniSafeRegisterNativeMethods, MatchJniDescriptorWithFunctionType) {
+  using namespace nativehelper::detail;
+  // Bad C++ signature.
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kCriticalNative, TestJni::bad_cptr, "()V");
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kNormalNative, TestJni::bad_cptr, "()V");
+
+  // JNI type descriptor is not legal (by itself).
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kCriticalNative, TestJni::v_, "BAD");
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kNormalNative, TestJni::v_eo, "BAD");
+
+  // Number of parameters in signature vs C++ function does not match.
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kCriticalNative, TestJni::v_i, "()V");
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kNormalNative, TestJni::v_eoo, "()V");
+
+  // Return types don't match.
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kCriticalNative, TestJni::v_, "()Z");
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kFastNative, TestJni::v_eo, "()Z");
+
+  // Argument types don't match.
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kCriticalNative, TestJni::v_i, "(Z)V");
+  EXPECT_NO_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kNormalNative, TestJni::v_eoo, "(Ljava/lang/Class;)V");
+
+  // OK.
+  EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kCriticalNative, TestJni::v_i, "(I)V");
+  EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kNormalNative, TestJni::v_eoo, "(Ljava/lang/Object;)V");
+
+  EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kCriticalNative, TestJni::v_lib, "(JIZ)V");
+  EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kNormalNative, TestJni::v_eolib, "(JIZ)V");
+  EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kCriticalNative, TestJni::s_lib, "(JIZ)S");
+  EXPECT_MATCH_JNI_DESCRIPTOR_AGAINST_FUNCTION(kNormalNative, TestJni::s_eolAibA, "([JI[Z)S");
+}
+
+TEST(JniSafeRegisterNativeMethods, Infer) {
+  using namespace nativehelper::detail;
+  {
+    using Infer_v_eolib_t = InferJniDescriptor<kNormalNative,
+                                               decltype(TestJni::v_eolib),
+                                               TestJni::v_eolib>;
+    EXPECT_CONSTEXPR_EQ(6u, Infer_v_eolib_t::kMaxStringSize);
+    std::string x = Infer_v_eolib_t::GetStringAtRuntime();
+    EXPECT_STRINGIFY_EQ("(JIZ)V", x.c_str());
+  }
+
+  {
+    using Infer_v_eolib_t = InferJniDescriptor<kNormalNative,
+                                               decltype(TestJni::s_eolAibA),
+                                               TestJni::s_eolAibA>;
+    EXPECT_STRINGIFY_EQ("args={[J,I,[Z}, ret=S", Infer_v_eolib_t::FromFunctionType().value());
+    EXPECT_CONSTEXPR_EQ(8u, Infer_v_eolib_t::kMaxStringSize);
+    std::string x = Infer_v_eolib_t::GetStringAtRuntime();
+    EXPECT_STRINGIFY_EQ("([JI[Z)S", x.c_str());
+  }
+}
+
+// Test the macro definition only. See other tests above for signature-match testing.
+TEST(JniSafeRegisterNativeMethods, MakeCheckedJniNativeMethod) {
+  // Ensure the temporary variables don't conflict with other local vars of same name.
+  JNINativeMethod tmp_native_method;  // shadow test.
+  (void) tmp_native_method;
+  bool is_signature_valid = true;  // shadow test.
+  (void) is_signature_valid;
+
+  // Ensure it works with critical.
+  {
+    JNINativeMethod m =
+        MAKE_CHECKED_JNI_NATIVE_METHOD(kCriticalNative,
+                                       "v_lib",
+                                       "(JIZ)V",
+                                       TestJni::v_lib);
+    (void)m;
+  }
+
+  // Ensure it works with normal.
+  {
+    JNINativeMethod m =
+        MAKE_CHECKED_JNI_NATIVE_METHOD(kNormalNative,
+                                       "v_eolib",
+                                       "(JIZ)V",
+                                       TestJni::v_eolib);
+    (void)m;
+  }
+
+  // Make sure macros properly expand inside of an array.
+  {
+    JNINativeMethod m_array[] = {
+        MAKE_CHECKED_JNI_NATIVE_METHOD(kCriticalNative,
+                                       "v_lib",
+                                       "(JIZ)V",
+                                       TestJni::v_lib),
+        MAKE_CHECKED_JNI_NATIVE_METHOD(kNormalNative,
+                                       "v_eolib",
+                                       "(JIZ)V",
+                                       TestJni::v_eolib),
+    };
+    (void)m_array;
+  }
+  {
+    JNINativeMethod m_array_direct[] {
+        MAKE_CHECKED_JNI_NATIVE_METHOD(kCriticalNative,
+                                       "v_lib",
+                                       "(JIZ)V",
+                                       TestJni::v_lib),
+        MAKE_CHECKED_JNI_NATIVE_METHOD(kNormalNative,
+                                       "v_eolib",
+                                       "(JIZ)V",
+                                       TestJni::v_eolib),
+    };
+    (void)m_array_direct;
+  }
+
+}
+
+static auto sTestCheckedAtFileScope =
+        MAKE_CHECKED_JNI_NATIVE_METHOD(kCriticalNative,
+                                       "v_lib",
+                                       "(JIZ)V",
+                                       TestJni::v_lib);
+
+static auto sTestInferredAtFileScope =
+        MAKE_INFERRED_JNI_NATIVE_METHOD(kCriticalNative,
+                                       "v_lib",
+                                       TestJni::v_lib);
+
+TEST(JniSafeRegisterNativeMethods, TestInferredJniNativeMethod) {
+  (void) sTestCheckedAtFileScope;
+  (void) sTestInferredAtFileScope;
+
+  // Ensure it works with critical.
+  {
+    JNINativeMethod m =
+        MAKE_INFERRED_JNI_NATIVE_METHOD(kCriticalNative,
+                                       "v_lib",
+                                       TestJni::v_lib);
+    (void)m;
+  }
+
+  // Ensure it works with normal.
+  {
+    JNINativeMethod m =
+        MAKE_INFERRED_JNI_NATIVE_METHOD(kNormalNative,
+                                       "v_eolib",
+                                       TestJni::v_eolib);
+    (void)m;
+  }
+}
+
+static void TestJniMacros_v_lib(jlong, jint, jboolean) {}
+static void TestJniMacros_v_lib_od(jlong, jint, jboolean) {}
+static void TestJniMacros_v_eolib(JNIEnv*, jobject, jlong, jint, jboolean) {}
+static void TestJniMacros_v_eolib_od(JNIEnv*, jobject, jlong, jint, jboolean) {}
+
+TEST(JniSafeRegisterNativeMethods, JniMacros) {
+  JNINativeMethod tmp_native_method;  // shadow variable check.
+  (void)tmp_native_method;
+  using Infer_t = int;  // shadow using check.
+  Infer_t unused;
+  (void)unused;
+
+  MAKE_JNI_CRITICAL_NATIVE_METHOD("v_lib", "(JIZ)V", TestJniMacros_v_lib);
+  MAKE_JNI_CRITICAL_NATIVE_METHOD_AUTOSIG("v_lib", TestJniMacros_v_lib);
+  CRITICAL_NATIVE_METHOD(TestJniMacros, v_lib, "(JIZ)V");
+  OVERLOADED_CRITICAL_NATIVE_METHOD(TestJniMacros, v_lib, "(JIZ)V", v_lib_od);
+  CRITICAL_NATIVE_METHOD_AUTOSIG(TestJniMacros, v_lib);
+
+  MAKE_JNI_FAST_NATIVE_METHOD("v_eolib", "(JIZ)V", TestJniMacros_v_eolib);
+  MAKE_JNI_FAST_NATIVE_METHOD_AUTOSIG("v_eolib", TestJniMacros_v_eolib);
+  FAST_NATIVE_METHOD(TestJniMacros, v_eolib, "(JIZ)V");
+  OVERLOADED_FAST_NATIVE_METHOD(TestJniMacros, v_eolib, "(JIZ)V", v_eolib_od);
+  FAST_NATIVE_METHOD_AUTOSIG(TestJniMacros, v_eolib);
+
+  MAKE_JNI_NATIVE_METHOD("v_eolib", "(JIZ)V", TestJniMacros_v_eolib);
+  MAKE_JNI_NATIVE_METHOD_AUTOSIG("v_eolib", TestJniMacros_v_eolib);
+  NATIVE_METHOD(TestJniMacros, v_eolib, "(JIZ)V");
+  OVERLOADED_NATIVE_METHOD(TestJniMacros, v_eolib, "(JIZ)V", v_eolib_od);
+  NATIVE_METHOD_AUTOSIG(TestJniMacros, v_eolib);
+
+  _NATIVEHELPER_JNI_MAKE_METHOD_OLD(kNormalNative, "v_eolib", "(JIZ)V", TestJniMacros_v_eolib);
+  tmp_native_method =
+      _NATIVEHELPER_JNI_MAKE_METHOD_OLD(kNormalNative, "v_eolib", "(JIZ)V", TestJniMacros_v_eolib);
+}