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

[LIU Hao <lh_mouse@126.com>]

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在 2022-11-20 20:53, Pali Rohár 写道:
> Hello! I would like to propose a new parameter for gcc: -mcrtdll= to
> allow specifying against which Windows C Runtime library should be
> binary linked. On Windows there are more crt libraries and currently gcc
> links to libmsvcrt.a which is in most cases symlink to libmsvcrt-os.a
> (but can be changed, e.g. during mingw-w64 building). mingw-w64 project
> already builds import .a library for every crt dll library (from the old
> crtdll.dll up to the new ucrtbase.dll), so it is ready for usage. Simple
> patch for gcc which implements -mcrtdll parameter is below. Note that on
> internet are other very similar patches for -mcrtdll= parameters and
> some are parts of custom mingw32 / mingw-w64 gcc builds. What do you
> think? Could gcc have "official" support for -mcrtdll= parameter?
> 
> 

It's not enough to just link against the desired library, you will also have to define 
`__MSVCRT_VERSION__` accordingly (for UCRT it should be defined as `0xE00` i.e. 14.0).

The current status of such mechanism is that both the macro `__MSVCRT_VERSION__` and the library 
'libmsvcrt.a' are determined when building mingw-w64, configurable by `--with-default-msvcrt=`, so 
they always match.


[1] https://sourceforge.net/p/mingw-w64/mailman/message/36030072/




-- 
Best regards,
LIU Hao


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