How to add files without extension in doxygen configuration file(e.g iostream library)?

In my configuration file in the INPUT tag I added one directory. Inside that iostream is there without any extension. After running the configuration file I'm not getting information related to iostream. I want to know how to add the files without extension in doxygen configuration file.

I created a small test example (contents is not that relevant for this test), file stdio:

/// the fie
void fie(void);

From the documentation (https://www.doxygen.nl/manual/config.html#cfg_extension_mapping):

EXTENSION_MAPPING

Doxygen selects the parser to use depending on the extension of the files it parses. With this tag you can assign which parser to use for a given extension. Doxygen has a built-in mapping, but you can override or extend it using this tag. The format is ext=language, where ext is a file extension, and language is one of the parsers supported by doxygen: IDL, Java, JavaScript, Csharp (C#), C, C++, D, PHP, md (Markdown), Objective-C, Python, Slice, VHDL, Fortran (fixed format Fortran: FortranFixed, free formatted Fortran: FortranFree, unknown formatted Fortran: Fortran. In the later case the parser tries to guess whether the code is fixed or free formatted code, this is the default for Fortran type files).

For instance to make doxygen treat .inc files as Fortran files (default is PHP), and .f files as C (default is Fortran), use: inc=Fortran f=C.

Note: For files without extension you can use no_extension as a placeholder. Note that for custom extensions you also need to set FILE_PATTERNS otherwise the files are not read by doxygen.

Here we see that the possibility for no_extension and with the following setting we get the requested information:

EXTRACT_ALL=YES
INPUT = stdio
EXTENSION_MAPPING = no_extension=C++

and I do see the stdio information.

Edit In case doesn't want to add all files one by one one hast to add * to FILE_PATTERNS.