[Bug 51435] New: iostream float formatting broken

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=51435

Bug ID: 51435
           Summary: iostream float formatting broken
           Product: Wine
           Version: 6.12
          Hardware: x86-64
                OS: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: msvcrt
          Assignee: [e-mail]
          Reporter: [e-mail]
      Distribution: ---

Created attachment 70288
  --> https://bugs.winehq.org/attachment.cgi?id=70288
test case solution demonstrating the error

On wine-6.12-162-gd10887b8f56

Full solution is in the attachment, but Wine is improperly formatting floats
when using printf "%g" or iostreams. A very simple example is:
    std::cout << 9.999999999999999e-5 << std::endl;

It should print "0.0001". It does print "0".

Of course, this affects much larger and more complicated programs, too.

Tested on Ubuntu 20.04, although I don't think it matters.