'?' replaced by '+'

Hi,

Is anyone aware of a clang feature that would replace the ‘?’ character from a random text file (interpreted as C through `-x c` though not containing C code) to replace it with ‘+’.
I’m running clang's preprocessor stage like this `clang -E -P -x c my_file.txt`.
I have no clue what’s happening, sadly I can’t experiment much as it’s not happening on my own machine as I’m trying to help someone who has that issue I can’t reproduce.

Thanks!

Nothing that springs to mind - might be some encoding issue. Check the
text encoding of the input and output files? Hexdump to verify exactly
what the character is?