[clang-format]: Inserts a space after u8 string literal modifiers in C: u8"My utf-8 string" -> u8 "My utf-8 string" and breaks compilation

[WillAvudim]

It worked with clang-format-17 just fine. After upgrading to clang-format-21 (latest dev as of April 4th 2025), it started inserting spaces between string literal type and the rest of the literal.
WAS: u8"My UTF-8 string"
BECOMES: u8 "My UTF-8 string"

Needless to say that this breaks compilation.

It's weird that it still works in C++ just fine, only C is broken.

I played with all the configuration parameters that could be related but couldn't find anything fixing this. Reverting all settings to an empty (default) configuration and trying various defaults doesn't help either: it's broken disregarding the defaults or any other settings.

[llvmbot]

@llvm/issue-subscribers-clang-format

Author: None (WillAvudim)

It worked with clang 17 just fine. After upgrading to clang 21 (latest dev as of April 4th 2025), it started inserting spaces between string literal type and the rest of the literal. WAS: u8"My UTF-8 string" BECOMES: u8 "My UTF-8 string"

Needless to say that this is breaks compilation.

It's weird that it still works in C++ just fine, only C is broken.

I played with all the configuration parameters that could be related but couldn't find anything related. Reverting all settings to an empty (default) configuration and trying various defaults doesn't help either: it's broken disregarding the defaults or any other settings.