[libc++] Implement P1147R1 (Printing volatile T*)

Differential Revision: https://reviews.llvm.org/D113482

libcxx/docs/Status/Cxx2bPapers.csv

@@ -27,7 +27,7 @@
 "`P0798R8 <https://wg21.link/P0798R8>`__","LWG","Monadic operations for ``std::optional``","October 2021","",""
 "`P0849R8 <https://wg21.link/P0849R8>`__","LWG","``auto(x)``: ``DECAY_COPY`` in the language","October 2021","",""
 "`P1072R10 <https://wg21.link/P1072R10>`__","LWG","``basic_string::resize_and_overwrite``","October 2021","",""
-"`P1147R1 <https://wg21.link/P1147R1>`__","LWG","Printing ``volatile`` Pointers","October 2021","",""
+"`P1147R1 <https://wg21.link/P1147R1>`__","LWG","Printing ``volatile`` Pointers","October 2021","|Complete|","14.0"
 "`P1272R4 <https://wg21.link/P1272R4>`__","LWG","Byteswapping for fun&&nuf","October 2021","",""
 "`P1675R2 <https://wg21.link/P1675R2>`__","LWG","``rethrow_exception`` must be allowed to copy","October 2021","",""
 "`P2077R3 <https://wg21.link/P2077R3>`__","LWG","Heterogeneous erasure overloads for associative containers","October 2021","",""

libcxx/include/ostream

@@ -55,6 +55,7 @@ public:
     basic_ostream& operator<<(double f);
     basic_ostream& operator<<(long double f);
     basic_ostream& operator<<(const void* p);
+    basic_ostream& operator<<(const volatile void* val); // C++23
     basic_ostream& operator<<(basic_streambuf<char_type,traits>* sb);
     basic_ostream& operator<<(nullptr_t);
 
@@ -210,6 +211,14 @@ public:
     basic_ostream& operator<<(double __f);
     basic_ostream& operator<<(long double __f);
     basic_ostream& operator<<(const void* __p);
+
+#if _LIBCPP_STD_VER > 20
+    _LIBCPP_HIDE_FROM_ABI
+    basic_ostream& operator<<(const volatile void* __p) {
+        return operator<<(const_cast<const void*>(__p));
+    }
+#endif
+
     basic_ostream& operator<<(basic_streambuf<char_type, traits_type>* __sb);
 
     _LIBCPP_INLINE_VISIBILITY

libcxx/test/std/input.output/iostream.format/output.streams/ostream.formatted/ostream.inserters.arithmetic/pointer.volatile.pass.cpp

@@ -0,0 +1,77 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <ostream>
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
+// template <class charT, class traits = char_traits<charT> >
+//   class basic_ostream;
+
+// basic_ostream& operator<<(const volatile void* val);
+
+#include <ostream>
+#include <cassert>
+
+template <class CharT>
+class testbuf : public std::basic_streambuf<CharT> {
+  typedef std::basic_streambuf<CharT> base;
+  std::basic_string<CharT> str_;
+
+public:
+  testbuf() {}
+
+  std::basic_string<CharT> str() const { return std::basic_string<CharT>(base::pbase(), base::pptr()); }
+
+protected:
+  virtual typename base::int_type overflow(typename base::int_type ch = base::traits_type::eof()) {
+    if (ch != base::traits_type::eof()) {
+      int n = static_cast<int>(str_.size());
+      str_.push_back(static_cast<CharT>(ch));
+      str_.resize(str_.capacity());
+      base::setp(const_cast<CharT*>(str_.data()), const_cast<CharT*>(str_.data() + str_.size()));
+      base::pbump(n + 1);
+    }
+    return ch;
+  }
+};
+
+int main(int, char**) {
+  testbuf<char> sb1;
+  std::ostream os1(&sb1);
+  int n1;
+  os1 << &n1;
+  assert(os1.good());
+  std::string s1 = sb1.str();
+
+  testbuf<char> sb2;
+  std::ostream os2(&sb2);
+  os2 << static_cast<volatile void*>(&n1);
+  assert(os2.good());
+  std::string s2 = sb2.str();
+
+  testbuf<char> sb3;
+  std::ostream os3(&sb3);
+  volatile int n3;
+  os3 << &n3;
+  assert(os3.good());
+  std::string s3 = sb3.str();
+
+  // %p is implementation defined. Instead of validating the
+  // output, at least ensure that it does not generate an empty
+  // string. Also make sure that given two distinct addresses, the
+  // output of %p is different.
+  assert(!s1.empty());
+  assert(!s2.empty());
+  assert(s1 == s2);
+
+  assert(!s3.empty());
+  assert(s2 != s3);
+
+  return 0;
+}