only .o, not .mod file is created

I try to compile a source code, normally .o and .mod files are both generated. But I experience one case that only the .o file, and no corresponding .mod file, is created.
The compilation doesn’t give me any error for this file. To compile the main file it need the .mod files of the associated modules, and this broke the compilation.
Could someone tell me a solution?


My mistake, I named the module and the file differently.