Bug 2314420

With the 12.0.0 release of mingw-w64 the default C runtime supported has changed from MSVCRT to UCRT. However, the Fedora build hasn't been updated to use the appropriate build-time configuration. As a result all toolchains in Fedora 41 target UCRT.

The release notes are here:

   https://sourceforge.net/p/mingw-w64/mingw-w64/ci/master/tree/mingw-w64-doc/howto-build/ucrt-vs-msvcrt.txt

They say:

   Users who wish to continue using msvcrt.dll can easily do so by
   adding the --with-default-msvcrt=msvcrt argument to both the
   mingw-w64-headers and mingw-w64-crt configure scripts.

However, looking at the RPM spec file for mingw-crt 12.0.0-3.fc41 I see:

%build
pushd mingw-w64-crt
    # Filter out -fstack-protector and -lssp from LDFLAGS as libssp is not yet potentially built with the bootstrap gcc
    MINGW32_LDFLAGS="`echo %{mingw32_ldflags} | sed 's|-fstack-protector||' | sed 's|-lssp||'`"
    MINGW64_LDFLAGS="`echo %{mingw64_ldflags} | sed 's|-fstack-protector||' | sed 's|-lssp||'`"
    MINGW64_CONFIGURE_ARGS="--disable-lib32"
    UCRT64_LDFLAGS="`echo %{ucrt64_ldflags} | sed 's|-fstack-protector||' | sed 's|-lssp||'`"
    UCRT64_CONFIGURE_ARGS="--disable-lib32 --with-default-msvcrt=ucrt"
    %mingw_configure
    %mingw_make_build
popd

I believe the correct configure arguments are now:

   MINGW64_CONFIGURE_ARGS="--disable-lib32 --with-default-msvcrt=msvcrt"
   UCRT64_CONFIGURE_ARGS="--disable-lib32"


Reproducible: Always

Steps to Reproduce:
I tested this by building a Windows application using the x86_64-w64-mingw32 toolchain. The resulting executable failed to run on a system without UCRT.

Performing the same build with the x86_64-w64-mingw32ucrt toolchain resulted in an executable which was identical to the other (apart from the timestamp and checksum in the PE header).