Re: [Mingw-w64-public] gcc parameter -mcrtdll= for choosing Windows C RunTime DLL library

[Matthew Brett <matthew.brett@lis.ac.uk>]

Hi,

On Sun, Nov 20, 2022 at 3:59 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > Date: Sun, 20 Nov 2022 16:44:08 +0100
> > From: Pali Rohár <pali.rohar@gmail.com>
> > Cc: gcc@gcc.gnu.org, mingw-w64-public@lists.sourceforge.net
> >
> > > Installing a redistributable is a nuisance, and dependence on non-system
> > > libraries might make the program non-free.
> >
> > On new windows versions they may be preinstalled (depends on newness of
> > windows version).
>
> I'm talking about older ones.  It is customary nowadays to build on Windows
> 11 and then run on Windows 8.
>
> > And if your application uses features unavailable in
> > older (or default) crt versions then this make application code
> > simplifier. Also redistributable packages are in most cases installed by
> > Windows update mechanism, which could be marked as system library. But
> > well, this is more license discussion than development discussion...
>
> I mentioned that because people might inadvertently build GPL'ed GNU
> software using this option, and violate the GPL without knowing it.  This is
> relevant to those who read this list and port GNU software to MS-Windows.
>
> > > > Note that with this option, you can also choose older version than the
> > > > default one (WinXP msvcrt.dll). So e.g. you can choose msvcrt20.dll or
> > > > crtdll.dll for older Windows version.
> > >
> > > Using the OS default MSVCRT already gets me that, at zero cost.
> >
> > Here "OS default MSVCRT" means Windows XP MSVCRT.DLL.
> >
> > On older windows versions there is no pre-installed MSVCRT.DLL. There
> > is MSVCRT20.DLL or CRTDLL.DLL (based on oldness of windows version). So
> > it is not at zero cost, you have yo either do that nuisance and install
> > MSVCRT.DLL as you write above or switch to older CRT version which is in
> > OS preinstalled.
>
> I never saw any problems with programs linked against MSVCRT.DLL, on all
> versions of Windows from XP up to Windows 10.  None.

It's hard to argue that it is rarely necessary or desirable to link to
- say - UCRT.  If it was, then we would not have the UCRT toolchains.
And in our particular case (Python extension modules) we need to use
UCRT linking to be compatible with the UCRT-linked standard Python
binary installs.

Cheers,

Matthew