You can (not) control the Unicode support via the CMake `FMT_UNICODE` option.

[grooverdan]

version: 11.0.0

It looks like its true, but you can't compile on MSVC without it.

As a subproject the option needs to be enabled for the target_compile_options to be applied.

include/fmt/base.h forces the define to true.

Line 457 will assert if the /utf8 isn't set.

ref: https://buildbot.mariadb.org/#/builders/234/builds/30730/steps/8/logs/stdio

[vitaut]

Thanks for reporting. Just to clarify: are you trying to disable Unicode support? Setting FMT_UNICODE macro was missing from the CMake config which is fixed in e50c8b6.

[grooverdan]

I just noticed it was there. I'm happy to enable unicode.

[vitaut]

Closing as disabling Unicode has been fixed but if there is more to it please let me know.

[Cazadorro]

I don't think this is fixed when using CUDA, tried with out cuda and it worked, but when using CUDA, the same exact /utf8 error:

Repos\cuda_experiments\cmake-build-debug\vcpkg_installed\x64-windows\include\fmt\base.h(465):
 error: static assertion failed with "Unicode support requires compiling with /utf-8"
  static_assert(!1 || use_utf8,

In fact, I don't see /utf-8 passed to CUDA when using fmt through vcpkg (october 2025 release).

nvcc.exe -forward-unknown-to-host-compiler -DFMT_SHARED -isystem Repos\cuda_experiments\cmake-build-debug\vcpkg_installed\x64-windows\include --allow-unsupported-compiler -D_WINDOWS -Xcompiler=" /EHsc" -Xcompiler=" -Ob0 -Od" -std=c++20 "--generate-code=arch=compute_75,code=[compute_75,sm_75]" -Xcompiler=-MDd -Xcompiler=-RTC1 -Xcompiler=-Zi --expt-relaxed-constexpr -MD -MT CMakeFiles\cuda_experiments.dir\main.cu.obj -MF CMakeFiles\cuda_experiments.dir\main.cu.obj.d -x cu -c Repos\cuda_experiments\main.cu -o CMakeFiles\cuda_experiments.dir\main.cu.obj -Xcompiler=-FdCMakeFiles\cuda_experiments.dir\,-FS

[Cazadorro]

Never mind, it appears to just be this issue #4167