Problems with lposix on win32

[Chris Marrin <chris@...>]

I have been trying to port lposix to compile and link under MSDev. The 
problem is that MSDev does not support many of the Posix capabilities. 
For instance there is no fork() function in Win32 and MSDev has no 
wrapper for it. This is true for many other Posix functions.

The natural solution is to use Cygwin. I can build lposix with Cygwin 
just fine. The problem comes in linking. The rest of my app 
(http://emma3d.org) builds Lua as a dll, so all the various components 
can share the interpreter. This is important because Emma is an 
extensible system. You can build an extension dll which can access the 
interpreter. So the interpreter needs to be a DLL.

The problem is that Cygwin can't link with a DLL produced by MSDev, so I 
can use GCC to link lposix. And MSDev can't link with an object produced 
by GCC (or more properly MSDev can't link with the Cygwin libraries that 
object needs). I can't build liblua.dll using Cygwin because then I 
would have to build every subsystem that links with that dll in Cygwin, 
and that is not acceptable for our app.

So I would like to suggest that we go back to the plan to make the 
'osex' package small and have it grow. We can still start with lposix, 
but toss the problematic function calls. To be honest, I'm not sure how 
practical fork() and some of the permission related calls are in many 
systems anyway.

Here is what lposix has today:

"access", "chdir", "chmod", "chown", "ctermid", "dir", "errno",
"exec", "files", "fork", "getcwd", "getenv", "getgroup",
"getlogin", "getpasswd", "getprocessid", "kill", "link",
"mkdir", "mkfifo", "pathconf", "putenv", "readlink", "rmdir",
"setgid", "setuid", "sleep", "stat", "symlink", "sysconf",
"times", "ttyname", "umask", "uname", "unlink", "utime", "wait"

Here is what I think we should take from it:

"access", "chdir", "chmod", "errno", "exec", "getcwd",
"getenv", "mkdir", "putenv", "rmdir", "sleep", "stat",
"umask"

Of the things left out, the only thing I think missing is "dir" and 
"files". These are the directory traversal functions. I left them out 
because Win32 does this sort of thing very differently. I can implement 
it pretty easily, but with a totally different stream of code. So I will 
do it later. I know there are other ideas out there about how to do 
directory traversal, so we should probably discuss and agree on a design.

I have ported all the above to Win32, using MSDev 7.1. Issues in porting 
to Win32:

1) Windows has the concept of permissions, but not for 
user/group/others. So I made it so that setting permissions for any of 
these sets the Win32 notion of permission. For instance, if you set read 
permission for user or group or other, I set read permission. (Note: 
cygwin seems to support full permissions for win32 files, looking at the 
'ls -l' command in the cygwin shell. How do they do that?)

2) Windows has no notion of an executable bit, so I just ignore it

3) Windows supports the notion of regular files, directories and 
character files, but not links, block files, fifos or sockets. So I 
ignore them.

4) Since Win32 has a Sleep function that takes milliseconds, I decided 
to change the implementation of sleep to take a double seconds value 
rather than an integer. On Win32 this means you get resolution down to 
1ms. And I used nanosleep() for the Linux implementation which gives 
resolution down to 1ns (dependent on the machine resolution, of course). 
If nanosleep does not exist elsewhere, we can always use something else, 
like sleep(), and just have 1sec resolution.

Comments?

--
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