[llvm-bugs] [Bug 145249] [clang-format] Formatting a C file only works with Cpp formatting settings

[LLVM Bugs via llvm-bugs]

Issue	145249
Summary	[clang-format] Formatting a C file only works with Cpp formatting settings
Labels	clang-format
Assignees
Reporter	hueychen27

    Let this be the file, `unformatted.c`, to be formatted in the examples:
```c
 int      main(int  argc , char  * argv [] ) {
     int * thing;
    int *eee;
}
```

This will not format the C code at all as `clang-format` returns `Configuration file(s) do(es) not support C++:`
```yaml
---
Language: C

IndentWidth: 9
PointerAlignment: Left
```

Adding `BaseOnStyle: LLVM` to the top of the file will run without an error, but the custom settings defined are ignored:
```yaml
BasedOnStyle: LLVM
---
Language: C

IndentWidth: 9
PointerAlignment: Left
```
Formatted file:
```c
int main(int argc, char *argv[]) {
  int *thing;
  int *eee;
}
```
For some reason, changing `Language: C` to use Cpp works.
```yaml
BasedOnStyle: LLVM
---
Language: Cpp

IndentWidth: 9
PointerAlignment: Left
```
Formatted file:
```c
int main(int argc, char* argv[]) {
 int* thing;
         int* eee;
}
```
Why is `Language: C` ignored?

clang-format version:
```
$ clang-format-21 --version
Debian clang-format version 21.0.0 (++20250612091244+3f0cf742ac4e-1~exp1)
```

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