[libc++] Ensure that all public C++ headers include <__assert>

This patch changes the requirement for getting the declaration of the
assertion handler from including <__assert> to including any public
C++ header of the library. Note that C compatibility headers are
excluded because we don't implement all the C headers ourselves --
some of them are taken straight from the C library, like assert.h.

It also adds a generated test to check it. Furthermore, this new
generated test is designed in a way that will make it possible to
replace almost all the existing test-generation scripts with this
system in upcoming patches.

Differential Revision: https://reviews.llvm.org/D122506

Author: ldionne

libcxx/docs/UsingLibcxx.rst

@@ -733,6 +733,7 @@ template <class BidirectionalIterator, class Compare>
 
 */
 
+#include <__assert> // all public C++ headers provide the assertion handler
 #include <__bits>
 #include <__config>
 #include <__debug>

libcxx/include/algorithm

@@ -80,6 +80,7 @@ namespace std {
 
 */
 
+#include <__assert> // all public C++ headers provide the assertion handler
 #include <__availability>
 #include <__config>
 #include <__utility/forward.h>

libcxx/include/any

@@ -112,7 +112,7 @@ template <size_t I, class T, size_t N> const T&& get(const array<T, N>&&) noexce
 #include <__algorithm/fill_n.h>
 #include <__algorithm/lexicographical_compare.h>
 #include <__algorithm/swap_ranges.h>
-#include <__assert>
+#include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <__tuple>
 #include <__utility/integer_sequence.h>

libcxx/include/array

@@ -518,6 +518,7 @@ template <class T>
 
 */
 
+#include <__assert> // all public C++ headers provide the assertion handler
 #include <__availability>
 #include <__chrono/duration.h>
 #include <__config>

libcxx/include/atomic

@@ -45,6 +45,7 @@ namespace std
 
 */
 
+#include <__assert> // all public C++ headers provide the assertion handler
 #include <__availability>
 #include <__config>
 #include <__thread/timed_backoff_policy.h>

libcxx/include/barrier

@@ -61,7 +61,7 @@ namespace std {
 
 */
 
-#include <__assert>
+#include <__assert> // all public C++ headers provide the assertion handler
 #include <__bit/bit_cast.h>
 #include <__bit/byteswap.h>
 #include <__bits> // __libcpp_clz

libcxx/include/bit

@@ -113,6 +113,7 @@ template <size_t N> struct hash<std::bitset<N>>;
 */
 
 #include <__algorithm/fill.h>
+#include <__assert> // all public C++ headers provide the assertion handler
 #include <__bit_reference>
 #include <__config>
 #include <__functional/unary_function.h>

libcxx/include/bitset

@@ -16,6 +16,7 @@ Macros:
 
 */
 
+#include <__assert> // all public C++ headers provide the assertion handler
 #include <__config>
 #include <assert.h>
 

libcxx/include/cassert

@@ -17,12 +17,11 @@
 
 */
 
+#include <__assert> // all public C++ headers provide the assertion handler
 #include <complex>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
-// hh 080623 Created
-
 #endif // _LIBCPP_CCOMPLEX