Build fails on Debian 13: fmt cannot format ICU UErrorCode in src/utils/slugify.cpp

[crystarm]

Environment

• OS: Debian GNU/Linux 13 (trixie)
• Kernel: 6.12.74+deb13+1-amd64
• Compiler: g++ 14.2.0
• CMake: 3.31.6
• Python: 3.13.5
• Ninja: 1.12.1
• libfmt-dev: 10.1.1+ds1-4
• libicu-dev: 76.1-4
• libre2-dev: 20240702-3+b1
• libabsl-dev: 20240722.0-4

Reproduction

1. Configure:
   cmake -B build_release -DCMAKE_BUILD_TYPE=Release -DCMAKE_EXPORT_COMPILE_COMMANDS=ON -DUSERVER_FORCE_DOWNLOAD_RE2=ON
2. Build:
   cmake --build build_release -j 8 --target realmedium_sample

What happened

The build failed in src/utils/slugify.cpp at fmt::format(..., status), where status is ICU’s UErrorCode. On Debian 13 with fmt 10.1.x, this type is not considered formattable, so compilation stops with Cannot format an argument and type_is_unformattable_for<UErrorCode, char>. This is not a runtime service bug, but a compile-time type-formatting incompatibility.

Check the attached log!! repro.log

[crystarm]

Created a PR with a fix for this issue: #29