Add SDCC Language for Eclipse CDT
https://nodamushi.github.io/nodamushi_sdcc/
Unlicense
Open "Language Mappings" page of your project property (right click on your project → "Properties" → "C/C++ General" → "Language Mappings") or the preferences("Window" menu -> "Preferences" -> "C/C++ General" -> "Language Mappings").
After that, click "Add" button and set the Languages of "C Source File" content type and "C Header File" content type to "SDCC".
If you already open C file editors, close them and reopen.