On Mon, 20 Oct 2025, Pali Rohár wrote:
I understand your concerns. This code is also using lower level WinAPI
calls and constants and also direct ntdll.dll syscalls which is also not
so well documented and in most cases marked as "can be changed".
Oh, I missed that bit (I didn't read the patch that far). Even more reason
to stay away from doing it...
More times, I hit the problem that I cannot simply read binary file from
stdin and freopen "fix" did not work. So we are in situation that
applications do not use freopen stdin because it does not work with
existing toolchains.
Indeed; the canonical way of doing this so far is using _setmode. It's of
course a little harder to discover, when the supposedly standard function
for doing it doesn't work.
And providing the fix into toolchain is harder as
it needs to touch internals of CRT and low level ntdll.dll calls which
of course makes sense to not take it as it has a questionable usage.
One idea: The primary motivation of this change is ability to switch
binary/text mode. What about reducing the freopen-NULL ability to just
change the 'b', 't' and ',ccs=' flags with completely ignoring all
others? This can be done by the _setmode() function (fifth step only)
and do not need to touch any internals.
That would be much more acceptables, yes.
It is something which is useful? Or it is worse to have such
reduced/incomplete implementation and it is really better to rather do
not change the existing freopen support provided by mingw-w64?
That is a good question - I'm not sure.
In one sense, it would make the common case of switching stdin/stdout to
binary mode much more discoverable, using standard C99 functions. But on
the other hand, it also fragments the Windows development landscape -
users code end up silently depending on this, while the same code does
compile fine on MSVC, but just not working in the same way.
I'm not sure if it is better to have such a half-support for the feature
or not. Especially as there is no existing code out there that does
this...
What do the other regulars think about this?
// Martin
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