--- /dev/null
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: libcpp-has-no-stdin, libcpp-has-no-stdout
+
+// Make sure that the iostreams are initialized before everything else.
+// This has been an issue when statically linking libc++ in some contexts.
+// See https://llvm.org/PR28954 for details.
+//
+// This test works by checking that std::{cin,cout,cerr} is the same in a
+// static object constructor and in the main function. It dumps the memory of
+// each stream in the static object constructor and compares it with the memory
+// in the main function.
+//
+// The assumption is that if there are no uses of the stream object (such as
+// construction), then its memory must be the same. In the case where the test
+// "fails" and we are actually accessing an uninitialized object when we perform
+// the memcpy, the behavior is technically undefined (so the test could still
+// pass).
+
+#include <cassert>
+#include <cstring>
+#include <iostream>
+
+struct Checker {
+ char *cerr_mem_dump;
+ char *cin_mem_dump;
+ char *cout_mem_dump;
+ char *clog_mem_dump;
+
+ char *wcerr_mem_dump;
+ char *wcin_mem_dump;
+ char *wcout_mem_dump;
+ char *wclog_mem_dump;
+
+ Checker()
+ : cerr_mem_dump(new char[sizeof(std::cerr)])
+ , cin_mem_dump(new char[sizeof(std::cin)])
+ , cout_mem_dump(new char[sizeof(std::cout)])
+ , clog_mem_dump(new char[sizeof(std::clog)])
+
+ , wcerr_mem_dump(new char[sizeof(std::wcerr)])
+ , wcin_mem_dump(new char[sizeof(std::wcin)])
+ , wcout_mem_dump(new char[sizeof(std::wcout)])
+ , wclog_mem_dump(new char[sizeof(std::wclog)])
+ {
+ std::memcpy(cerr_mem_dump, (char*)&std::cerr, sizeof(std::cerr));
+ std::memcpy(cin_mem_dump, (char*)&std::cin, sizeof(std::cin));
+ std::memcpy(cout_mem_dump, (char*)&std::cout, sizeof(std::cout));
+ std::memcpy(clog_mem_dump, (char*)&std::clog, sizeof(std::clog));
+
+ std::memcpy(wcerr_mem_dump, (char*)&std::wcerr, sizeof(std::wcerr));
+ std::memcpy(wcin_mem_dump, (char*)&std::wcin, sizeof(std::wcin));
+ std::memcpy(wcout_mem_dump, (char*)&std::wcout, sizeof(std::wcout));
+ std::memcpy(wclog_mem_dump, (char*)&std::wclog, sizeof(std::wclog));
+ }
+
+ ~Checker() {
+ delete[] cerr_mem_dump;
+ delete[] cin_mem_dump;
+ delete[] cout_mem_dump;
+ delete[] clog_mem_dump;
+
+ delete[] wcerr_mem_dump;
+ delete[] wcin_mem_dump;
+ delete[] wcout_mem_dump;
+ delete[] wclog_mem_dump;
+ }
+};
+
+static Checker check;
+
+int main() {
+ assert(std::memcmp(check.cerr_mem_dump, (char const*)&std::cerr, sizeof(std::cerr)) == 0);
+ assert(std::memcmp(check.cin_mem_dump, (char const*)&std::cin, sizeof(std::cin)) == 0);
+ assert(std::memcmp(check.cout_mem_dump, (char const*)&std::cout, sizeof(std::cout)) == 0);
+ assert(std::memcmp(check.clog_mem_dump, (char const*)&std::clog, sizeof(std::clog)) == 0);
+
+ assert(std::memcmp(check.wcerr_mem_dump, (char const*)&std::wcerr, sizeof(std::wcerr)) == 0);
+ assert(std::memcmp(check.wcin_mem_dump, (char const*)&std::wcin, sizeof(std::wcin)) == 0);
+ assert(std::memcmp(check.wcout_mem_dump, (char const*)&std::wcout, sizeof(std::wcout)) == 0);
+ assert(std::memcmp(check.wclog_mem_dump, (char const*)&std::wclog, sizeof(std::wclog)) == 0);
+}