Implement more open flags and define -D_COMPILING_NEWLIB

[bartoldeman]

Implement O_CREAT, O_TRUNC, O_EXCL, O_APPEND in _open, and do proper prototyping via _COMPILING_NEWLIB.

[tkchia]

Hello @bartoldeman ,

Thank you!

Now that you mention O_TRUNC, I now think the special case of int $0x21 with %ah == 0x40, %cx == 0 should probably be factored out into a separate function -- perhaps an ftruncate ( ) function -- and then O_TRUNC changed to use that.

Then we can modify _write ( ) so that write (..., 0) has the correct POSIX-ish semantics (i.e. it does nothing or just checks for errors).

I will merge your changes first, and then try to make this change.

[bartoldeman]

Indeed. There is also the issue of naming: in Borland compilers and DJGPP, _open(), _write(), and a few other functions are not the same as open() and co but simpler functions that just wrap int21, with DJGPP doing a little bit more too. MSVC and (Open)Watcom, and also DJGPP, use _dos_open and co for this purpose.

It just happened that the initial implementation of libgloss/ia16 _open, _write and co pretty much matched the Borland style implementation but this was by accident I presume.

See e.g. http://www.delorie.com/djgpp/doc/libc/libc_601.html

Perhaps the libgloss "BSP" functions should use open, write etc then (with two underscores) for DOS compiler compatibility?

[tkchia]

Hello @bartoldeman ,

Hmm... my thinking (at least for now) is that _dos_open and friends might be useful to have. But I am not sure if they should be used to underlie the functions open, write, etc. --- or if it might be better to put them into, say, a separate library of DOS-specific functions.

Thank you!