Add tests for all C11 headers.

Well, all except <threads.h> which we have no current plans to implement.

The only thing this turned up is that clang's <float.h> doesn't define
FLT_HAS_SUBNORM/DBL_HAS_SUBNORM/LDBL_HAS_SUBNORM, so for now we assert
that those are missing so that when we get a fixed clang, we notice.

Also the <tgmath.h> is utterly perfunctory, but seems like an appropriate
amount of effort to put in.

Bug: N/A
Test: ran tests
Change-Id: I7f7a7040b3271ceda625bee8a40a9d8cef52ee44
diff --git a/tests/float_test.cpp b/tests/float_test.cpp
new file mode 100644
index 0000000..a75214e
--- /dev/null
+++ b/tests/float_test.cpp
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+#include <gtest/gtest.h>
+
+#include <float.h>
+
+TEST(float_h, macros) {
+#if !defined(FLT_RADIX)
+#error FLT_RADIX
+#endif
+#if !defined(DECIMAL_DIG)
+#error DECIMAL_DIG
+#endif
+#if !defined(FLT_DECIMAL_DIG)
+#error FLT_DECIMAL_DIG
+#endif
+#if !defined(DBL_DECIMAL_DIG)
+#error DBL_DECIMAL_DIG
+#endif
+#if !defined(LDBL_DECIMAL_DIG)
+#error LDBL_DECIMAL_DIG
+#endif
+#if !defined(FLT_MIN)
+#error FLT_MIN
+#endif
+#if !defined(DBL_MIN)
+#error DBL_MIN
+#endif
+#if !defined(LDBL_MIN)
+#error LDBL_MIN
+#endif
+#if !defined(FLT_EPSILON)
+#error FLT_EPSILON
+#endif
+#if !defined(DBL_EPSILON)
+#error DBL_EPSILON
+#endif
+#if !defined(LDBL_EPSILON)
+#error LDBL_EPSILON
+#endif
+#if !defined(FLT_DIG)
+#error FLT_DIG
+#endif
+#if !defined(DBL_DIG)
+#error DBL_DIG
+#endif
+#if !defined(LDBL_DIG)
+#error LDBL_DIG
+#endif
+#if !defined(FLT_MANT_DIG)
+#error FLT_MANT_DIG
+#endif
+#if !defined(DBL_MANT_DIG)
+#error DBL_MANT_DIG
+#endif
+#if !defined(LDBL_MANT_DIG)
+#error LDBL_MANT_DIG
+#endif
+#if !defined(FLT_MIN_EXP)
+#error FLT_MIN_EXP
+#endif
+#if !defined(DBL_MIN_EXP)
+#error DBL_MIN_EXP
+#endif
+#if !defined(LDBL_MIN_EXP)
+#error LDBL_MIN_EXP
+#endif
+#if !defined(FLT_MIN_10_EXP)
+#error FLT_MIN_10_EXP
+#endif
+#if !defined(DBL_MIN_10_EXP)
+#error DBL_MIN_10_EXP
+#endif
+#if !defined(LDBL_MIN_10_EXP)
+#error LDBL_MIN_10_EXP
+#endif
+#if !defined(FLT_MAX_EXP)
+#error FLT_MAX_EXP
+#endif
+#if !defined(DBL_MAX_EXP)
+#error DBL_MAX_EXP
+#endif
+#if !defined(LDBL_MAX_EXP)
+#error LDBL_MAX_EXP
+#endif
+#if !defined(FLT_MAX_10_EXP)
+#error FLT_MAX_10_EXP
+#endif
+#if !defined(DBL_MAX_10_EXP)
+#error DBL_MAX_10_EXP
+#endif
+#if !defined(LDBL_MAX_10_EXP)
+#error LDBL_MAX_10_EXP
+#endif
+#if !defined(FLT_ROUNDS)
+#error FLT_ROUNDS
+#endif
+#if !defined(FLT_EVAL_METHOD)
+#error FLT_EVAL_METHOD
+#endif
+// TODO: FLT_HAS_SUBNORM currently missing from clang. Negate this test when fixed.
+#if defined(FLT_HAS_SUBNORM)
+#error FLT_HAS_SUBNORM
+#endif
+// TODO: DBL_HAS_SUBNORM currently missing from clang. Negate this test when fixed.
+#if defined(DBL_HAS_SUBNORM)
+#error DBL_HAS_SUBNORM
+#endif
+// TODO: LDBL_HAS_SUBNORM currently missing from clang. Negate this test when fixed.
+#if defined(LDBL_HAS_SUBNORM)
+#error LDBL_HAS_SUBNORM
+#endif
+}