[libcxx-commits] [libcxx] [libc++][print] Adds ostream overloads. (PR #73262)

[Louis Dionne via libcxx-commits]

================
@@ -1195,6 +1209,140 @@ extern template class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostream<char>;
 extern template class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostream<wchar_t>;
 #endif
 
+#if _LIBCPP_STD_VER >= 23
+
+template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
+_LIBCPP_HIDE_FROM_ABI inline void
+__vprint_nonunicode(ostream& __os, string_view __fmt, format_args __args, bool __write_nl) {
+  ostream::sentry __s(__os);
+  if (__s) {
+    string __o = vformat(__os.getloc(), __fmt, __args);
+    if (__write_nl)
+      __o += '\n';
+
+    const char* __str = __o.data();
+    size_t __len      = __o.size();
+
+#  ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    try {
+#  endif // _LIBCPP_HAS_NO_EXCEPTIONS
+      typedef ostreambuf_iterator<char> _Ip;
+      if (std::__pad_and_output(
+              _Ip(__os),
+              __str,
+              (__os.flags() & ios_base::adjustfield) == ios_base::left ? __str + __len : __str,
+              __str + __len,
+              __os,
+              __os.fill())
+              .failed())
+        __os.setstate(ios_base::badbit | ios_base::failbit);
+
+#  ifndef _LIBCPP_HAS_NO_EXCEPTIONS
+    } catch (...) {
+      __os.__set_badbit_and_consider_rethrow();
+    }
+#  endif // _LIBCPP_HAS_NO_EXCEPTIONS
+  }
+}
+
+template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
+_LIBCPP_HIDE_FROM_ABI inline void vprint_nonunicode(ostream& __os, string_view __fmt, format_args __args) {
+  std::__vprint_nonunicode(__os, __fmt, __args, false);
+}
+
+// Returns the FILE* associated with the __os.
+// Returns a nullptr when no FILE* is associated with __os.
+// This function is in the dylib since the type of the buffer associated
+// with std::cout, std::cerr, and std::clog is only known in the dylib.
+//
+// This function implements part of the implementation-defined behavior
+// of [ostream.formatted.print]/3
+//   If the function is vprint_unicode and os is a stream that refers to
+//   a terminal capable of displaying Unicode which is determined in an
+//   implementation-defined manner, writes out to the terminal using the
+//   native Unicode API;
+// Whether the returned FILE* is "a terminal capable of displaying Unicode"
+// is determined in the same way as the print(FILE*, ...) overloads.
+_LIBCPP_AVAILABILITY_PRINT _LIBCPP_EXPORTED_FROM_ABI FILE* __get_ostream_file(ostream& __os);
+
+#  ifndef _LIBCPP_HAS_NO_UNICODE
+template <class = void> // TODO PRINT template or availability markup fires too eagerly (http://llvm.org/PR61563).
+_LIBCPP_AVAILABILITY_PRINT _LIBCPP_HIDE_FROM_ABI void
----------------
ldionne wrote:

In a follow-up, we could use `_LIBCPP_AVAILABILITY_HAS_PRINT` to check whether we have `__get_ostream_file` on the current deployment target. If we don't, we could instead assume that `!__file` and use `__vprint_nonunicode`. That would make this *mostly* work for older deployment targets, except for the `flush` below. But by and far, users could use `<print>` on older deployment targets with no issues.

We could then even remove the availability annotations on `__vprint_unicode` and others, since they would basically have no deployment target requirements anymore.

https://github.com/llvm/llvm-project/pull/73262