I did a very quick test and it seems that _O_{U8|U16|W}TEXT translation modes
are working starting with msvcrt40.dll, so we shouldn't bother about this being
an issue for msvcrt20.dll and older.
assert.h already maps assert to _wassert when _UNICODE or UNICODE macros are
defined. I think we could just extend this condition to include
`__MSVCRT_VERSION__ >= 0x0800 || defined (_UCRT)`, and if we want to do it for
msvcrt.dll, `__MSVCRT_VERSION__ == 0x0600`.
The only drawback I see is that stored strings will be wchar[] instead of
char[], resulting in larger binaries.
________________________________
From: Pali Rohár <[email protected]>
Sent: Tuesday, September 9, 2025 2:15 AM
To: Kirill Makurin <[email protected]>
Cc: mingw-w64-public <[email protected]>
Subject: Re: Always map assert to _wassert for msvcr80.dll and later?
Now I see that MS documents that _O_U8TEXT does not work together with
printf and hence the assert does not print anything when _O_U8TEXT is
set on stderr.
https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/setmode
Instead of redirecting the assert via #define to _wassert, I would
rather propose to overrride _assert symbol for those affected import
libraries and fix it to work also for _O_U8TEXT.
On Monday 08 September 2025 19:03:09 Pali Rohár wrote:
> Hello,
>
> This is not problem of assert, but rather of the fprintf which assert
> calls. Same problem can be triggered by using the plain fprintf(stderr,...)
> instead of assert(0).
>
> So I do not think that it makes sense to remap assert as basically all
> functions which calls fprintf(stderr,...) are affected.
>
> Is not it just the _O_U8TEXT which is broken?
>
> On Monday 08 September 2025 15:38:09 Kirill Makurin wrote:
> > Consider the following code:
> >
> > ```
> > #include <assert.h>
> > #include <fcntl.h>
> > #include <io.h>
> > #include <stdio.h>
> >
> > int main (void) {
> > _setmode (_fileno (stderr), _O_U8TEXT);
> > assert (0);
> > return 0;
> > }
> > ```
> >
> > When compiled with MSVC, it properly prints message about failed assertion.
> > When it is compiled with mingw-w64's headers (Msys2/UCRT64) it produces no
> > output.
> >
> > mingw-w64's assert.h maps assert() macro to _wassert only when _UNICODE or
> > UNICODE is defined. MSVC's assert.h always maps assert() macro to _wassert
> > and even no longer exposes _assert function.
> >
> > How about we always map assert() macro to _wassert for msvcr80.dll and
> > later? Since we also emulate _wassert for msvcrt.dll, it should be OK to
> > map it to _wassert for msvcrt.dll as well.
> >
> > - Kirill Makurin
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