Re: _set_fmode?

[Greg Chicares <gchicares at sbcglobal dot net>]

On 2009-03-18 09:43Z, Corinna Vinschen wrote:
> On Mar 17 21:15, Charles Wilson wrote:
>> Is there a cygwin analogue to the msvc _set_fmode()? That is, a function
>> that sets the default mode of fopen, even if you don't explicitly
>> specify it "rb" or whatever.
>> 
>> Obviously, there's "use binary (or text) mounts".  Less obviously, you
>> can link against /usr/lib/binary.o (or -lbinmode), or text.o (or
>> automode.o or textreadmode.o and the similar .a's).  But I'm looking for
>> an actual function call to replace the following code in libarchive:
>> 
>> +#if defined(_WIN32) && !defined(__CYGWIN__)
> 
> The !defined(__CYGWIN__) is not necessary because gcc for Cygwin doesn't
> define _WIN32.
> 
>>    /* Make sure open() function will be used with a binary mode. */
>>    /* on cygwin, we need something similar, but instead link against */
>>    /* a special startup object, binmode.o */
>>    _set_fmode(_O_BINARY);
>>  #endif
>> 
>> I'm using binmode.o at present, but I'd prefer to just make a func call
>> at the same place the WIN32-specific code does.  (FWIW, you can't call
>> the w32api _set_fmode() function and expect it to work; the msvc runtime
>> and cygwin maintain different default _fmode variables).
> 
> Cygwin has no such function call except for the per-descriptor function
> setmode (fd, mode).  IMHO using binmode.o is much more elegant.  The
> only other choice you have is this:
> 
>   extern int _fmode;
>   _fmode = O_BINARY;
> 
> _fmode is defined in crt0.o so you can simply access it if you like.
> But anyway, using binmode.o is much more elegant, IMHO.  I don't see
> what speaks against using it.

If a drop-in replacement for _set_fmode() is nonetheless still wanted,
then _mingw32_init_fmode() here:
  http://cygwin.com/cgi-bin/cvsweb.cgi/src/winsup/mingw/crt1.c?cvsroot=src
might provide ideas for implementing it (or reasons to avoid it: for
example, standard streams would already have been opened before such a
function could be called).

An alternative that keeps all toolchains working the same way is to
link with 'binmode.o' for Cygwin, and 'Binmode.obj' for msvc:
  http://msdn.microsoft.com/en-us/library/ee2849wt(VS.80).aspx
if it's acceptable to change the upstream package.

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