Header extension .h interpreted as C

[clangd]

Header extension .h interpreted as C

[VukanJ]

Sure, you just need to run :CocConfig and write the following line to your coc-settings.json file:

{
    "clangd.fallbackFlags" : ["-xc++ -othercompilerflagsofyourchoice"]
}

For my use cases, setting fallbackFlags to the compiler flags I always use is sufficient. But adding the -xc++ flag to compile_flags.txt works as well

[VukanJ]

I figured it out by myself: Setting the language flag -xc++ explicitly sets the language for all files. Sorry for the spam

[proc-moe]

Thanks, clangd interpreted .h as C++ in my machine, I solved it by adding -xc to compile_commands.json like this

[
  {
    "arguments": [
      "-xc"
      ]
    }
]

[Mikael-Pereira]

I know this is old but it helped a lot.
For those searching latter it might be useful to add, you can add this same argument in a .clangd file at the root of the source files (if you have project specific configs there) or in the global config.yaml file.

CompileFlags: Add: [ -xc++, -std=c++20, ]

For me it was complaining about -std=c++20:

clang: Invalid argument '-std=c++20' not allowed with 'C' [drv_argument_not_allowed_with]

For me he was treating all .h files as C headers.

[chvolow24]

can you please elaborate your solution?

Sure thing. In the root directory of your project, create a file called .clangd if it does not already exist. In that file, add any compiler flags you want clangd to emulate inside the square brackets, separated by commas:

CompileFlags:
    Add: [-xc]

(-xc is the one that fixed the issue for me)

Hope this works for you too!

[chvolow24]

I had a similar problem. clangd thought the.h files in my C project were "Objective-C++" (didn't even know that was a thing). I would contend that that is a bug, maybe to do with how libc is set up on MacOS. I finally fixed it after finding this thread and adding -xc to CompileFlags.

[yaoyhu]

can you please elaborate your solution?

Sure thing. In the root directory of your project, create a file called .clangd if it does not already exist. In that file, add any compiler flags you want clangd to emulate inside the square brackets, separated by commas:

CompileFlags:
    Add: [-xc]

(-xc is the one that fixed the issue for me)

Hope this works for you too!

Thanks! I think I have figured it out that it can't be done(set C & C++ standard at the same time in clangd.fallbackFlags) or it will cause the Invalid argument '-std=c99' not allowed with 'Objective-C++'clang error.

But still thanks for letting me know the -x flag in clang. Thanks!

For future readers:

1. https://stackoverflow.com/a/78185524/17001641
2. https://stackoverflow.com/a/19413311/17001641

[zhengweidi]

Hey, can you tell me how you solved this problem?

[zhengweidi]

Sure, you just need to run :CocConfig and write the following line to your coc-settings.json file:

{
    "clangd.fallbackFlags" : ["-xc++ -othercompilerflagsofyourchoice"]
}

For my use cases, setting fallbackFlags to the compiler flags I always use is sufficient. But adding the -xc++ flag to compile_flags.txt works as well

thx!

[yaoyhu]

I had a similar problem. clangd thought the.h files in my C project were "Objective-C++" (didn't even know that was a thing). I would contend that that is a bug, maybe to do with how libc is set up on MacOS. I finally fixed it after finding this thread and adding -xc to CompileFlags.

I'm experiencing the same error in vscode-clangd, can you please elaborate your solution?