Cygwin - preventing stdout/stderr redirection

SDL Development
1

Hey guys,

Is there a way to prevent (or work around) the stdout/stderr redirection
to stdout.txt and stderr.txt under Cgywin (without modifying the SDL
startup code :)? I’m running MingW32 library on SDL’s website. Thanks in
advance!

-Mark–
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.

2

Replying to my own post –

After poking around the SDL source, it looks like it’s not possible to
prevent or undo stdout/stderr redirection under Windows without source
modification.

Further poking ::poke, poke:: shows only Windows and Macintosh do this.
I understand why it’d be useful on Macintosh. I understand why it’d be
useful on VC++. But it’s definitely not necessary on MinGW or Cygwin
development (redirection can be used if file output is needed.)

If this is gonna be done, doesn’t it make sense to be able to turn the
console output feature on/off? At least save stdout and stderr file
handlers so things can be written to the console if necessary?

For example, it’d be nice to be able to print usage information (progname --help). This is common on X11, and I think even some Windows apps
(though not many) do this. It’s an open-source-ism if nothing else.

-MarkOn Fri, 1 Feb 2002, Mark K. Kim wrote:

Hey guys,

Is there a way to prevent (or work around) the stdout/stderr redirection
to stdout.txt and stderr.txt under Cgywin (without modifying the SDL
startup code :)? I’m running MingW32 library on SDL’s website. Thanks in
advance!

-Mark

–
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

–
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.

3

I haven’t tested it, but i’d expect you could print usage info
to the console if you do it before SDL_Init–
Dave Brondsema

— “Mark K. Kim” wrote:

Replying to my own post –

After poking around the SDL source, it looks like it’s not
possible to
prevent or undo stdout/stderr redirection under Windows
without source
modification.

Further poking ::poke, poke:: shows only Windows and Macintosh
do this.
I understand why it’d be useful on Macintosh. I understand
why it’d be
useful on VC++. But it’s definitely not necessary on MinGW or
Cygwin
development (redirection can be used if file output is
needed.)

If this is gonna be done, doesn’t it make sense to be able to
turn the
console output feature on/off? At least save stdout and
stderr file
handlers so things can be written to the console if necessary?

For example, it’d be nice to be able to print usage
information (progname --help). This is common on X11, and I think even some
Windows apps
(though not many) do this. It’s an open-source-ism if nothing
else.

-Mark

On Fri, 1 Feb 2002, Mark K. Kim wrote:

Hey guys,

Is there a way to prevent (or work around) the stdout/stderr
redirection
to stdout.txt and stderr.txt under Cgywin (without modifying
the SDL
startup code :)? I’m running MingW32 library on SDL’s
website. Thanks in
advance!

-Mark

–
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

–
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

Do You Yahoo!?
Great stuff seeking new owners in Yahoo! Auctions!
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4

The redirection occurs before main() by SDL’s startup code.

How this happens is quite clever (one might say :). For compatibility,
your code is supposed to start at “main()”. But Windows actually starts
at “WinMain()”, and the “WinMain()” symbol is linked into the SDL library
(so you can’t override it). Furthermore, “main”'s symbol is changed to
"SDL_main" by passing “-Dmain=SDL_main” to gcc. This symbol
manipulation is actually not necessary on Windows, but seems to exist for
compatibility reasons (there was a discussion earlier in the mailing list
about the necessity of mainpulating “main”; I didn’t understand what that
was about until yesterday :). The redirection is accomplished inside
"WinMain()" by “freopen()”-ing “stdin” and “stdout” before "WinMain()"
calls “SDL_main()”.

Anyway, that’s why stdin/stdout redirection can’t be overridden – because
SDL does it before “main()” is even called! Hmmm… now that I think of
it, perhaps symbol manipulation by the linker could be used, but I’d like
to discuss the possibility of SDL support to work around it nicely.

-MarkOn Sat, 2 Feb 2002, Dave Brondsema wrote:

I haven’t tested it, but i’d expect you could print usage info
to the console if you do it before SDL_Init

–
Dave Brondsema

— “Mark K. Kim” wrote:

Replying to my own post –

After poking around the SDL source, it looks like it’s not
possible to
prevent or undo stdout/stderr redirection under Windows
without source
modification.

Further poking ::poke, poke:: shows only Windows and Macintosh
do this.
I understand why it’d be useful on Macintosh. I understand
why it’d be
useful on VC++. But it’s definitely not necessary on MinGW or
Cygwin
development (redirection can be used if file output is
needed.)

If this is gonna be done, doesn’t it make sense to be able to
turn the
console output feature on/off? At least save stdout and
stderr file
handlers so things can be written to the console if necessary?

For example, it’d be nice to be able to print usage
information (progname --help). This is common on X11, and I think even some
Windows apps
(though not many) do this. It’s an open-source-ism if nothing
else.

-Mark

On Fri, 1 Feb 2002, Mark K. Kim wrote:

Hey guys,

Is there a way to prevent (or work around) the stdout/stderr
redirection
to stdout.txt and stderr.txt under Cgywin (without modifying
the SDL
startup code :)? I’m running MingW32 library on SDL’s
website. Thanks in
advance!

-Mark

–
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

–
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

Do You Yahoo!?
Great stuff seeking new owners in Yahoo! Auctions!
http://auctions.yahoo.com

SDL mailing list
SDL at libsdl.org
http://www.libsdl.org/mailman/listinfo/sdl

–
Mark K. Kim
http://www.cbreak.org/mark/
PGP key available upon request.

5

The redirection occurs before main() by SDL’s startup code.

The reason this is done is so that professional applications don’t have
a text console pop up by default. If you want to have the text console,
write your application as a console app, and just modify SDL_main.c, which
is in the public domain.

See ya,
-Sam Lantinga, Software Engineer, Blizzard Entertainment