[Bug libstdc++/102259] New: ifstream::read(…, count) fails when count >= 2^31 on darwin

["mimomorin at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102259

            Bug ID: 102259
           Summary: ifstream::read(…, count) fails when count >= 2^31 on
                    darwin
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mimomorin at gmail dot com
  Target Milestone: ---

Created attachment 51431
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51431&action=edit
Testcase for ifstream::read(…, count >= 2^31)

I tried to read a large file using `ifstream::read` on Mac, but it fails to
read any byte when count >= 2^31. Note that the system is 64-bit and
`std::streamsize` has 8 bytes.
Here is a testcase.

#include <iostream>
#include <fstream>
int main() {
    std::ifstream is{"2GB.bin", std::ios::binary}; // filesize >= 2^31 bytes
    auto buffer = new char[1LL << 31];
    is.read(buffer, 1LL << 31);
    std::cout << is.good() << " (" << is.gcount() << " bytes)\n";
    // Expected output: "1 (2147483648 bytes)"
    // Actual output (on Mac): "0 (0 bytes)"
}

My system is macOS 10.15 running on x86_64 Mac. The testcase failed on
Homebrew's GCC (ver. 6, 9, 10, 11) and MacPorts' GCC (ver. 6), but it succeeded
on LLVM Clang (trunk) and Apple Clang (ver. 12).

`ifstream::read(…, count)` works fine when count < 2^31. So if we split 
    is.read(buffer, 1LL << 31);
into
    is.read(buffer, (1LL << 31) - 1);
    is.read(buffer + (1LL << 31) - 1, 1);
then everything goes OK.
Additionally, `istringstream::read(…, count >= 2^31)` works fine both on GCC
and Clang.

I don't think this simple issue went unnoticed, so maybe I've missed something.