TWIMC,
Some time ago, I reported that fork() didn't work when running the current cygwin distro on the AMD64 on Windows. At the time, I debugged far enough to get an approximate picture of what Cygwin was doing with VirtualXXX calls to implement fork, and I posted some questions in the hopes of understanding it well enough to try to make a fix. As far as I could see, I didn't get a reply.
To summarize, it seemed to me as if the code was making some assumptions about what virtual addresses ranges would be available and assigned under certain conditions related to fork, and that these assumptions were not valid on the AMD64, leading to failures.
Presumably, a ground-rule of Cygwin is to program only to the documented Win32 API, and not to resort to the NT API substrate as illustrated in Nebbett.
In any case, the offer is still open; if someone would be so kind as to offer up a summary of the design of fork(), I'd be willing to make some effort to diagnose and propose mods to adapt it.
Since this hasn't been answered by more knowledgeable people, I'll stick my neck out. No, I don't believe anyone has found satisfactory support for fork() within the documented Win32 API. Thus, cygwin is easily broken by changes which Microsoft has made in the various "64-bit" Windows versions. I do believe Cygwin has ground rules of running only on released Windows versions for which cgf has been provided a working hardware platform. If you're talking about the Physical Address Extension Windows with 48-bit virtual/40-bit physical- addressing for AMD64, that meets neither of those criteria. Apparently, no one has been willing to provide any "64-bit" Windows hardware for the Cygwin project, even for the released ia64 Windows. If you don't have more time than I to look at the source and try to understand how fork() was implemented, I think you're wasting bandwidth. Likewise, if you're proposing supporting a version of Windows which Microsoft will not permit the Cygwin project to use. If you're talking about standard released 32-bit Windows running on an AMD, my impression is there should be no problem.
Tim Prince
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