RFC: consider dropping support for old MSYS/MinGW

[rprichard]

If anyone sees this and is currently using winpty with old MSYS/MinGW (not MSYS2 or MinGW-w64), please let me know!

The old MSYS/MinGW environment is lacking relative to MSYS2/MinGW-w64 and MSVC in various ways. It would be convenient for me if winpty did not support it anymore.

Issues with native compilation ("MinGW"):

• winpty uses DACLs to secure its named pipes, and Windows provides functions to convert between SIDs/SDs and strings. winpty doesn't actually use these functions (because they're slow), but it has convenience C++ wrappers for the APIs to aid in debugging. MinGW (a) doesn't define the SD functions, (b) doesn't define SDDL_VERSION, and (c) defines ConvertStringSidToSidW incorrectly. [src]

• MinGW does not define the "LVB" console cell attributes. [src1] [src2]

• MinGW provides an swprintf matching VC6's prototype. Unlike the other compilers, its swprintf doesn't conform to C99. vsnprintf is provided, but requires passing -std=g++11 even though vsnprintf is part of C99 (and therefore C++11). [src]

• MinGW lacks PIPE_REJECT_REMOTE_CLIENTS. [src]

• MinGW lacks MAPVK_VK_TO_VSC. [src] [added 2017-01-31]

• MinGW lacks the new version-checking APIs that MSVC and MinGW-w64 provide.[src]

• Parallel make hangs -- parallel mingw32-make works better but tends to interleave output on a byte-by-byte basis. [src]

Issues with the UNIX adapter ("MSYS"):

• While the MinGW project updates its native-targeting (the "MinGW") toolchain, the MSYS-targeting toolchain is permanently locked at GCC 3.4.x, which lacks support for things like std::wstring and modern C++.

• The native code uses pre-compiled headers, but the UNIX adapter must compile without them because MSYS GCC doesn't support them.

• select can return EAGAIN. Contemporary Cygwin/MSYS2 can return EINTR, but not EAGAIN. [src]

• At some point after MSYS forked Cygwin, the path conversion APIs were deprecated, and new ones were introduced. The winpty UNIX adapter supports both APIs. [src]

• MSYS does not support the static-libstdc++ compiler option. [src]

• MSYS lacks the pipe2 API. [commit]

• Miscellaneous bugs in MSYS:

  • [cygwin_internal]
  • [mb<->wcs conversions]
  • [printf %ls]

• MSYS errno isn't thread-local. [added 2017-02-01]

• MSYS lacks wcscpy and wcscat. [added 2017-02-01]

[rprichard]

I've noticed recently that MSYS winpty tends to crash:

rprichard@ATOM-W10 /c/rprichard/proj/winpty
$ ./build/winpty ls
error reading from internal wakeup pipe: error 0
      0 [sig] winpty 4908 open_stackdumpfile: Dumping stack trace to winpty.exe.stackdump
LICENSE   README.md    VERSION.txt  config.mk  misc  src          winpty.exe.stackdump
Makefile  RELEASES.md  build        configure  ship  vcbuild.bat
Aborted (core dumped)

I think this is a race condition involving errno -- read fails and sets errno to something, but errno is reset to 0 by another thread. errno is thread-local on all non-obsolete systems. The fix is probably to kill off the MSYS winpty support. To start, I'll probably omit the MSYS package from the next release.